Thứ Tư, ngày 09 tháng 4 năm 2014

SQL SERVER – Find Row Count in Table – Find Largest Table in Database.

SELECT sc.name +'.'+ ta.name TableName
 ,SUM(pa.rows) RowCnt
 FROM sys.tables ta
 INNER JOIN sys.partitions pa
 ON pa.OBJECT_ID = ta.OBJECT_ID
 INNER JOIN sys.schemas sc
 ON ta.schema_id = sc.schema_id
 WHERE ta.is_ms_shipped = 0 AND pa.index_id IN (1,0)
 GROUP BY sc.name,ta.name
 ORDER BY SUM(pa.rows) DESC
More:

to get all tables in a database:
select * from INFORMATION_SCHEMA.TABLES
to get all columns in a database:
select * from INFORMATION_SCHEMA.columns
to get all views in a db:
select * from INFORMATION_SCHEMA.TABLES where table_type = 'view'

Thứ Tư, ngày 19 tháng 3 năm 2014

How to enable fingerprint device for Thinkpad L430 in Ubuntu 13.10

Supported readers (run command lsusb to find out the ID of your reader)
============
  045e:00bb        061a:0110        147e:1002
  045e:00bc        08ff:1600        147e:1003
  045e:00bd        08ff:2500        147e:2015
  045e:00ca        08ff:2580        147e:2016
  0483:2015        08ff:5501        147e:3000
  0483:2016        138a:0001        147e:3001
  05ba:0007        147e:1000        147e:5002
  05ba:0008        147e:1001        147e:5003
  05ba:000a

Installation

  1. First of all, if you have installed Fingerprint GUI manually before, get rid of it completely. Remove all binaries, shared libraries, any other files and undo all the changes you have made to your system config files (especially to files under /etc/pam.d/).
  2. Add this PPA to your sources:
    sudo add-apt-repository ppa:fingerprint/fingerprint-gui
    sudo apt-get update
    
  3. Install the packages:
    sudo apt-get install libbsapi policykit-1-fingerprint-gui fingerprint-gui
    
  4. Log out of your session and log back in (we need the new session defaults to be picked up).

Setup

After installation launch Fingerprint GUI (can be found under System > Preferences) and enrol your fingerprints.
That should be all you need to do!
Try locking your screen, logging out and in, sudo in terminal and running graphical apps requiring root privileges.

Thứ Hai, ngày 03 tháng 3 năm 2014

Removing accents (and diacritics) in any language from Java

Removing accents (and diacritics) in any language from Java


import java.text.Normalizer;
import java.text.Normalizer.Form;

// ...

public static String removeAccents(String text) {
    return text == null ? null
        : Normalizer.normalize(text, Form.NFD)
            .replaceAll("\\p{InCombiningDiacriticalMarks}+", "");
}

or 

 public static String deAccent(String str) {
     String nfdNormalizedString = Normalizer.normalize(str, Normalizer.Form.NFD); 
     Pattern pattern = Pattern.compile("\\p{InCombiningDiacriticalMarks}+");
     return pattern.matcher(nfdNormalizedString).replaceAll(""); 
        } 

Thứ Hai, ngày 24 tháng 2 năm 2014

Signatures couldn't be verified because the public key is not available: NO_PUBKEY

Eror PPA for GNOME Do Core Team ERROR:

...
Reading package lists... Done
W: GPG error: http://ppa.launchpad.net saucy Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 423A2125D782A00F
Reading package lists... Done
...

Solution:

apt-get update 2> /tmp/keymissing; for key in $(grep "NO_PUBKEY" /tmp/keymissing |sed "s/.*NO_PUBKEY //"); do echo -e "\nProcessing key: $key"; gpg --keyserver subkeys.pgp.net --recv $key && sudo gpg --export --armor $key | apt-key add -; done

Thứ Năm, ngày 06 tháng 2 năm 2014

Spring Web Flow Reference Guide

Sample Code:

cd #
mkdir spring-samples
cd spring-samples
svn co https://github.com/SpringSource/spring-webflow-samples
cd spring-webflow-samples/trunk
mvn package


This chapter begins the Users Section. It shows how to implement flows using the flow definition language. By the end of this chapter you should have a good understanding of language constructs, and be capable of authoring a flow definition.

What is a flow?

A flow encapsulates a reusable sequence of steps that can execute in different contexts. Below is a Garrett Information Architecture diagram illustrating a reference to a flow that encapsulates the steps of a hotel booking process:
Site Map illustrating a reference to a flow

What is the makeup of a typical flow?

In Spring Web Flow, a flow consists of a series of steps called "states". Entering a state typically results in a view being displayed to the user. On that view, user events occur that are handled by the state. These events can trigger transitions to other states which result in view navigations.
The example below shows the structure of the book hotel flow referenced in the previous diagram:
Flow diagram

How are flows authored?

Flows are authored by web application developers using a simple XML-based flow definition language. The next steps of this guide will walk you through the elements of this language.

Essential language elements

flow

Every flow begins with the following root element:



   
All states of the flow are defined within this element. The first state defined becomes the flow's starting point.

view-state

Use the view-state element to define a step of the flow that renders a view:

   
By convention, a view-state maps its id to a view template in the directory where the flow is located. For example, the state above might render /WEB-INF/hotels/booking/enterBookingDetails.xhtml if the flow itself was located in the /WEB-INF/hotels/booking directory.

transition

Use the transition element to handle events that occur within a state:

    

   
These transitions drive view navigations.

end-state

Use the end-state element to define a flow outcome:

   
When a flow transitions to a end-state it terminates and the outcome is returned.

Checkpoint: Essential language elements

With the three elements view-statetransition, and end-state, you can quickly express your view navigation logic. Teams often do this before adding flow behaviors so they can focus on developing the user interface of the application with end users first. Below is a sample flow that implements its view navigation logic using these elements:


    
        
    
 
    
        
        
        
    
 
    

    
  
 
   

Actions

Most flows need to express more than just view navigation logic. Typically they also need to invoke business services of the application or other actions.
Within a flow, there are several points where you can execute actions. These points are:
  • On flow start
  • On state entry
  • On view render
  • On transition execution
  • On state exit
  • On flow end

Actions are defined using a concise expression language. Spring Web Flow uses the Unified EL by default. The next few sections will cover the essential language elements for defining actions.

evaluate

The action element you will use most often is the evaluate element. Use the evaluate element to evaluate an expression at a point within your flow. With this single tag you can invoke methods on Spring beans or any other flow variable. For example:
  
   

Assigning an evaluate result

If the expression returns a value, that value can be saved in the flow's data model called flowScope:

    

Converting an evaluate result

If the expression returns a value that may need to be converted, specify the desired type using the result-type attribute:

    

Checkpoint: flow actions

Now review the sample booking flow with actions added:


    

    
        
    

    
        
    
 
    
        
        
        
    
 
    

    
  
 
   
This flow now creates a Booking object in flow scope when it starts. The id of the hotel to book is obtained from a flow input attribute.

Input/Output Mapping

Each flow has a well-defined input/output contract. Flows can be passed input attributes when they start, and can return output attributes when they end. In this respect, calling a flow is conceptually similar to calling a method with the following signature:
FlowOutcome flowId(Map inputAttributes);
  
... where a FlowOutcome has the following signature:
public interface FlowOutcome {
   public String getName();          
   public Map getOutputAttributes();
}
  

input

Use the input element to declare a flow input attribute:

   
Input values are saved in flow scope under the name of the attribute. For example, the input above would be saved under the name hotelId.

Declaring an input type

Use the type attribute to declare the input attribute's type:

    
If an input value does not match the declared type, a type conversion will be attempted.

Assigning an input value

Use the value attribute to specify an expression to assign the input value to:

    
If the expression's value type can be determined, that metadata will be used for type coersion if no type attribute is specified.

Marking an input as required

Use the required attribute to enforce the input is not null or empty:

    

output

Use the output element to declare a flow output attribute. Output attributes are declared within end-states that represent specific flow outcomes.

      

   
Output values are obtained from flow scope under the name of the attribute. For example, the output above would be assigned the value of the bookingId variable.

Specifying the source of an output value

Use the value attribute to denote a specific output value expression:
  
    

Checkpoint: input/output mapping

Now review the sample booking flow with input/output mapping:


    

    
        
    

    
        
    
 
    
        
        
        
    
 
    
        
    

    
  
 
   
The flow now accepts a hotelId input attribute and returns a bookingId output attribute when a new booking is confirmed.

Variables

A flow may declare one or more instance variables. These variables are allocated when the flow starts. Any @Autowired transient references the variable holds are also rewired when the flow resumes.

var

Use the var element to declare a flow variable:

   
Make sure your variable's class implements java.io.Serializable, as the instance state is saved between flow requests.

Calling subflows

A flow may call another flow as a subflow. The flow will wait until the subflow returns, then respond to the subflow outcome.

subflow-state

Use the subflow-state element to call another flow as a subflow:

    
          
    
    

   
The above example calls the createGuest flow, then waits for it to return. When the flow returns with a guestCreated outcome, the new guest is added to the booking's guest list.

Passing a subflow input

Use the input element to pass input to the subflow:

    
    

    

Mapping subflow output

Simply refer to a subflow output attribute by its name within a outcome transition:

      

    
In the above example, guest is the name of an output attribute returned by the guestCreated outcome.

Checkpoint: calling subflows

Now review the sample booking flow calling a subflow:


    

    
        
    

    
        
    

    
        
        
        
        
    

    
        
              
        
        
    
  
    
        
    

    
  
  
   
The flow now calls a createGuest subflow to add a new guest to the guest list.

Chapter 4. Expression Language (EL)

Introduction

Web Flow uses EL to access its data model and to invoke actions. This chapter will familiarize you with EL syntax, configuration, and special EL variables you can reference from your flow definition.
EL is used for many things within a flow including:
  1. Access client data such as declaring flow inputs or referencing request parameters.
  2. Access data in Web Flow's RequestContext such as flowScope or currentEvent.
  3. Invoke methods on Spring-managed objects through actions.
  4. Resolve expressions such as state transition criteria, subflow ids, and view names.
EL is also used to bind form parameters to model objects and reversely to render formatted form fields from the properties of a model object. That however does not apply when using Web Flow with JSF in which case the standard JSF component lifecyle applies.

Expression types

An important concept to understand is there are two types of expressions in Web Flow: standard expressions and template expressions.

Standard Expressions

The first and most common type of expression is the standard expression. Such expressions are evaluated directly by the EL and need not be enclosed in delimiters like #{}. For example:

    
The expression above is a standard expression that invokes the nextPage method on the searchCriteria variable when evaluated. If you attempt to enclose this expression in a special delimiter like #{} you will get an IllegalArgumentException. In this context the delimiter is seen as redundant. The only acceptable value for the expression attribute is an single expression string.

Template expressions

The second type of expression is a template expression. A template expression allows mixing of literal text with one or more standard expressions. Each standard expression block is explicitly surrounded with the #{} delimiters. For example:

    
The expression above is a template expression. The result of evaluation will be a string that concatenates literal text such as error- and .xhtml with the result of evaluating externalContext.locale. As you can see, explicit delimiters are necessary here to demarcate standard expression blocks within the template.

Note

See the Web Flow XML schema for a complete listing of those XML attributes that accept standard expressions and those that accept template expressions. You can also use F2 in Eclipse (or equivalent shortcut in other IDEs) to access available documentation when typing out specific flow definition attributes.

EL Implementations

Spring EL

Starting with version 2.1 Web Flow uses the Spring Expression Language (Spring EL). Spring EL was created to provide is a single, well-supported expression language for use across all the products in the Spring portfolio. It is distributed as a separate jarorg.springframework.expression in the Spring Framework. Existing applications will need to remove dependencies on org.jboss.el or org.ognl and use org.springframework.expression instead. See the section below on EL Portability for other notes on upgrading.

Unified EL

In Web Flow 2.0 Unified EL was the default expression language with jboss-el as the implementation. Use of Unified EL also implies a dependency on el-api although that is typically provided by your web container. Tomcat 6 includes it, for example. Spring EL is the default and recommended expression language to use. However it is possible to replace it with Unified EL if you wish to do so. You need the following Spring configuration to plug in the WebFlowELExpressionParser to the flow-builder-services:



    
        
    

                
Note that if your application is registering custom converters it's important to ensure the WebFlowELExpressionParser is configured with the conversion service that has those custom converters.



    
        
    
    



                

OGNL

OGNL is the third supported expression language. OGNL is the EL most familiar to Web Flow version 1.0 users. Please refer to the OGNL language guide for specifics on its EL syntax. If you wish to use OGNL this is the Spring configuration necessary to plug it in:



                
Note that if your application is registering custom converters it's important to ensure the WebFlowOgnlExpressionParser is configured with the conversion service that has those custom converters.



    



                

EL portability

In general, you will find Spring EL, Unified EL and OGNL to have a very similar syntax.
Note however there are some advantages to Spring EL. For example Spring EL is closely integrated with the type conversion of Spring 3 and that allows you to take full advantage of its features. Specifically the automatic detection of generic types as well as the use of formatting annotations is currently supported with Spring EL only.
There are some minor changes to keep in mind when upgrading to Spring EL from Unified EL or OGNL as follows:
  1. Expressions deliniated with ${} in flow definitions must be changed to #{}.
  2. Expressions testing the current event #{currentEvent == 'submit'} must be changed to #{currentEvent.id == 'submit'}.
  3. Resolving properties such as #{currentUser.name} may cause NullPointerException without any checks such as #{currentUser != null ? currentUser.name : null}. A much better alternative though is the safe navigation operator #{currentUser?.name}.
For more information on Spring EL syntax please refer to the Language Reference section in the Spring Documentation.

Special EL variables

There are several implicit variables you may reference from within a flow. These variables are discussed in this section.
Keep in mind this general rule. Variables referring to data scopes (flowScope, viewScope, requestScope, etc.) should only be used when assigning a new variable to one of the scopes.
For example when assigning the result of the call to bookingService.findHotels(searchCriteria) to a new variable called "hotels" you must prefix it with a scope variable in order to let Web Flow know where you want it stored:


 

 
  
   
  
 
 

   
However when setting an existing variable such as "searchCriteria" in the example below, you reference the variable directly without prefixing it with any scope variables:


 

 
  
   
  
 


   

The following is the list of implicit variables you can reference within a flow definition:

flowScope

Use flowScope to assign a flow variable. Flow scope gets allocated when a flow starts and destroyed when the flow ends. With the default implementation, any objects stored in flow scope need to be Serializable.

   

viewScope

Use viewScope to assign a view variable. View scope gets allocated when a view-state enters and destroyed when the state exits. View scope is only referenceable from within a view-state. With the default implementation, any objects stored in view scope need to be Serializable.

    

   

requestScope

Use requestScope to assign a request variable. Request scope gets allocated when a flow is called and destroyed when the flow returns.

   

flashScope

Use flashScope to assign a flash variable. Flash scope gets allocated when a flow starts, cleared after every view render, and destroyed when the flow ends. With the default implementation, any objects stored in flash scope need to be Serializable.
    
   

conversationScope

Use conversationScope to assign a conversation variable. Conversation scope gets allocated when a top-level flow starts and destroyed when the top-level flow ends. Conversation scope is shared by a top-level flow and all of its subflows. With the default implementation, conversation scoped objects are stored in the HTTP session and should generally be Serializable to account for typical session replication.

   

requestParameters

Use requestParameters to access a client request parameter:

   

currentEvent

Use currentEvent to access attributes of the current Event:

   

currentUser

Use currentUser to access the authenticated Principal:

   

messageContext

Use messageContext to access a context for retrieving and creating flow execution messages, including error and success messages. See the MessageContext Javadocs for more information.

   

resourceBundle

Use resourceBundle to access a message resource.

   

flowRequestContext

Use flowRequestContext to access the RequestContext API, which is a representation of the current flow request. See the API Javadocs for more information.

flowExecutionContext

Use flowExecutionContext to access the FlowExecutionContext API, which is a representation of the current flow state. See the API Javadocs for more information.

flowExecutionUrl

Use flowExecutionUrl to access the context-relative URI for the current flow execution view-state.

externalContext

Use externalContext to access the client environment, including user session attributes. See the ExternalContext API JavaDocs for more information.

   

Scope searching algorithm

As mentioned earlier in this section when assigning a variable in one of the flow scopes, referencing that scope is required. For example:

  
When simply accessing a variable in one of the scopes, referencing the scope is optional. For example:

  
When no scope is specified, like in the use of booking above, a scope searching algorithm is used. The algorithm will look in request, flash, view, flow, and conversation scope for the variable. If no such variable is found, an EvaluationException will be thrown.

Chapter 5. Rendering views

Introduction

This chapter shows you how to use the view-state element to render views within a flow.

Defining view states

Use the view-state element to define a step of the flow that renders a view and waits for a user event to resume:

    

  
By convention, a view-state maps its id to a view template in the directory where the flow is located. For example, the state above might render /WEB-INF/hotels/booking/enterBookingDetails.xhtml if the flow itself was located in the /WEB-INF/hotels/booking directory.
Below is a sample directory structure showing views and other resources like message bundles co-located with their flow definition:
Flow Packaging

Specifying view identifiers

Use the view attribute to specify the id of the view to render explicitly.

Flow relative view ids

The view id may be a relative path to view resource in the flow's working directory:

   

Absolute view ids

The view id may be a absolute path to a view resource in the webapp root directory:

   

Logical view ids

With some view frameworks, such as Spring MVC's view framework, the view id may also be a logical identifier resolved by the framework:

   
See the Spring MVC integration section for more information on how to integrate with the MVC ViewResolver infrastructure.

View scope

A view-state allocates a new viewScope when it enters. This scope may be referenced within the view-state to assign variables that should live for the duration of the state. This scope is useful for manipulating objects over a series of requests from the same view, often Ajax requests. A view-state destroys its viewScope when it exits.

Allocating view variables

Use the var tag to declare a view variable. Like a flow variable, any @Autowired references are automatically restored when the view state resumes.

   

Assigning a viewScope variable

Use the on-render tag to assign a variable from an action result before the view renders:

    

   

Manipulating objects in view scope

Objects in view scope are often manipulated over a series of requests from the same view. The following example pages through a search results list. The list is updated in view scope before each render. Asynchronous event handlers modify the current data page, then request re-rendering of the search results fragment.

    
        
    
    
        
                    
    
    
        
                  
    

   

Executing render actions

Use the on-render element to execute one or more actions before view rendering. Render actions are executed on the initial render as well as any subsequent refreshes, including any partial re-renderings of the view.

    

     

Binding to a model

Use the model attribute to declare a model object the view binds to. This attribute is typically used in conjunction with views that render data controls, such as forms. It enables form data binding and validation behaviors to be driven from metadata on your model object.
The following example declares an enterBookingDetails state manipulates the booking model:

     
The model may be an object in any accessible scope, such as flowScope or viewScope. Specifying a model triggers the following behavior when a view event occurs:
  1. View-to-model binding. On view postback, user input values are bound to model object properties for you.
  2. Model validation. After binding, if the model object requires validation that validation logic will be invoked.
For a flow event to be generated that can drive a view state transition, model binding must complete successfully. If model binding fails, the view is re-rendered to allow the user to revise their edits.

Performing type conversion

When request parameters are used to populate the model (commonly referred to as data binding), type conversion is required to parse String-based request parameter values before setting target model properties. Default type conversion is available for many common Java types such as numbers, primitives, enums, and Dates. Users also have the ability to register their own type conversion logic for user-defined types, and to override the default Converters.

Type Conversion Options

Starting with version 2.1 Spring Web Flow uses the type conversion and formatting system introduced in Spring 3 for nearly all type conversion needs. Previously Web Flow applications used a type conversion mechanism that was different from the one in Spring MVC, which relied on thejava.beans.PropertyEditor abstraction. Spring 3 offers a modern type conversion alternative to PropertyEditors that was actually influenced by Web Flow's own type conversion system. Hence Web Flow users should find it natural to work with the new Spring 3 type conversion. Another obvious and very important benefit of this change is that a single type conversion mechanism can now be used across Spring MVC And Spring Web Flow.

Upgrading to Spring 3 Type Conversion And Formatting

What does this practically mean for existing applications? Existing applications are likely registering their own converters of type org.springframework.binding.convert.converters.Converter through a sub-class of DefaultConversionService available in Spring Binding. Those converters can continue to be registered as before. They will be adapted as Spring 3 GenericConverter types and registered with a Spring 3 org.springframework.core.convert.ConversionService instance. In other words existing converters will be invoked through Spring's type conversion service.
The only exception to this rule are named converters, which can be referenced from a binding element in a view-state:
public class ApplicationConversionService extends DefaultConversionService { 
    public ApplicationConversionService() {
        addDefaultConverters();
        addDefaultAliases();
        addConverter("customConverter", new CustomConverter());  
    }
}
    


    
        
    

    
Named converters are not supported and cannot be used with the type conversion service available in Spring 3. Therefore such converters will not be adapted and will continue to work as before, i.e. will not involve the Spring 3 type conversion. However, this mechanism is deprecated and applications are encouraged to favor Spring 3 type conversion and formatting features.
Also note that the existing Spring Binding DefaultConversionService no longer registers any default converters. Instead Web Flow now relies on the default type converters and formatters in Spring 3.
In summary the Spring 3 type conversion and formatting is now used almost exclusively in Web Flow. Although existing applications will work without any changes, we encourage moving towards unifying the type conversion needs of Spring MVC and Spring Web Flow parts of applications.

Configuring Type Conversion and Formatting

In Spring MVC an instance of a FormattingConversionService is created automatically through the custom MVC namespace:


 

    
Internally that is done with the help of FormattingConversionServiceFactoryBean, which registers a default set of converters and formatters. You can customize the conversion service instance used in Spring MVC through the conversion-service attribute:

    

In Web Flow an instance of a Spring Binding DefaultConversionService is created automatically, which does not register any converters. Instead it delegates to a FormattingConversionService instance for all type conversion needs. By default this is not the sameFormattingConversionService instance as the one used in Spring 3. However that won't make a practical difference until you start registering your own formatters.
The DefaultConversionService used in Web Flow can be customized through the flow-builder-services element:

    

Connecting the dots in order to register your own formatters for use in both Spring MVC and in Spring Web Flow you can do the following. Create a class to register your custom formatters:
public class ApplicationConversionServiceFactoryBean extends FormattingConversionServiceFactoryBean {

    @Override
    protected void installFormatters(FormatterRegistry registry) {
        // ...
    }
 
}    

    
Configure it for use in Spring MVC:


    
 
    

    
 

    
Connection the Web Flow DefaultConversionService to the same "applicationConversionService" bean used in Spring MVC:
    
     
    
     
    
     
    
    
Of course it is also possible to mix and match. Register new Spring 3 Formatter types through the "applicationConversionService". Register existing Spring Binding Converter types through the "defaultConversionService".

Working With Spring 3 Type Conversion And Formatting

An important concept to understand is the difference between type converters and formatters.
Type converters in Spring 3, provided in org.springframework.core, are for general-purpose type conversion between any two object types. In addition to the most simple Converter type, two other interfaces are ConverterFactory and GenericConverter.
Formatters in Spring 3, provided in org.springframework.context, have the more specialized purpose of representing Objects as Strings. The Formatter interface extends the Printer and Parser interfaces for converting an Object to a String and turning a String into an Object.
Web developers will find the Formatter interface most relevant because it fits the needs of web applications for type conversion.

Note

An important point to be made is that Object-to-Object conversion is a generalization of the more specific Object-to-String conversion. In fact in the end Formatters are reigstered as GenericConverter types with Spring's GenericConversionService making them equal to any other converter.

Formatting Annotations

One of the best features of the new type conversion is the ability to use annotations for a better control over formatting in a concise manner. Annotations can be placed on model attributes and on arguments of @Controller methods that are mapped to requests. Out of the box Spring provides two annotations NumberFormat and DateTimeFormat but you can create your own and have them registered along with the associated formatting logic. You can see examples of the DateTimeFormat annotation in the Spring Travel and in the Petcare along with other samples in the Spring Samples repository.

Working With Dates

The DateTimeFormat annotation implies use of Joda Time. If that is present on the classpath the use of this annotation is enabled automatically. By default neither Spring MVC nor Web Flow register any other date formatters or converters. Therefore it is important for applications to register a custom formatter to specify the default way for printing and parsing dates. The DateTimeFormat annotation on the other hand provides more fine-grained control where it is necessary to deviate from the default.
For more information on working with Spring 3 type conversion and formatting please refer to the relevant sections of the Spring documentation.

Suppressing binding

Use the bind attribute to suppress model binding and validation for particular view events. The following example suppresses binding when the cancel event occurs:

    
    

  

Specifying bindings explicitly

Use the binder element to configure the exact set of model bindings usable by the view. This is particularly useful in a Spring MVC environment for restricting the set of "allowed fields" per view.

    
        
        
        
        
    
    
    


  
If the binder element is not specified, all public properties of the model are eligible for binding by the view. With the binder element specified, only the explicitly configured bindings are allowed.
Each binding may also apply a converter to format the model property value for display in a custom manner. If no converter is specified, the default converter for the model property's type will be used.

    
        
            
        
        
        
        
    
    
    


  
In the example above, the shortDate converter is bound to the checkinDate and checkoutDate properties. Custom converters may be registered with the application's ConversionService.
Each binding may also apply a required check that will generate a validation error if the user provided value is null on form postback:

    
        
        
        
        
        
        
    
    
    

  
In the example above, all of the bindings are required. If one or more blank input values are bound, validation errors will be generated and the view will re-render with those errors.

Validating a model

Model validation is driven by constraints specified against a model object. Web Flow supports enforcing such constraints programatically as well as declaratively with JSR-303 Bean Validation annotations.

JSR-303 Bean Validation

Web Flow provides built-in support for the JSR-303 Bean Validation API building on equivalent support available in Spring MVC. To enable JSR-303 validation configure the flow-builder-services with Spring MVC's LocalValidatorFactoryBean:





   
With the above in place, the configured validator will be applied to all model attributes after data binding.
Note that JSR-303 bean validation and validation by convention (explained in the next section) are not mutually exclusive. In other words Web Flow will apply all available validation mechanisms.

Programmatic validation

There are two ways to perform model validation programatically. The first is to implement validation logic in your model object. The second is to implement an external Validator. Both ways provide you with a ValidationContext to record error messages and access information about the current user.

Implementing a model validate method

Defining validation logic in your model object is the simplest way to validate its state. Once such logic is structured according to Web Flow conventions, Web Flow will automatically invoke that logic during the view-state postback lifecycle. Web Flow conventions have you structure model validation logic by view-state, allowing you to easily validate the subset of model properties that are editable on that view. To do this, simply create a public method with the name validate${state}, where ${state} is the id of your view-state where you want validation to run. For example:
public class Booking {
    private Date checkinDate;
    private Date checkoutDate;
    ...
        
    public void validateEnterBookingDetails(ValidationContext context) {
        MessageContext messages = context.getMessageContext();
        if (checkinDate.before(today())) {
            messages.addMessage(new MessageBuilder().error().source("checkinDate").
                defaultText("Check in date must be a future date").build());
        } else if (!checkinDate.before(checkoutDate)) {
            messages.addMessage(new MessageBuilder().error().source("checkoutDate").
                defaultText("Check out date must be later than check in date").build());
        }
    }
}

     

In the example above, when a transition is triggered in a enterBookingDetails view-state that is editing a Booking model, Web Flow will invoke the validateEnterBookingDetails(ValidationContext) method automatically unless validation has been suppressed for that transition. An example of such a view-state is shown below:

    

     

Any number of validation methods are defined. Generally, a flow edits a model over a series of views. In that case, a validate method would be defined for each view-state where validation needs to run.

Implementing a Validator

The second way is to define a separate object, called a Validator, which validates your model object. To do this, first create a class whose name has the pattern ${model}Validator, where ${model} is the capitialized form of the model expression, such as booking. Then define a public method with the name validate${state}, where ${state} is the id of your view-state, such as enterBookingDetails. The class should then be deployed as a Spring bean. Any number of validation methods can be defined. For example:
@Component
public class BookingValidator {
    public void validateEnterBookingDetails(Booking booking, ValidationContext context) {
        MessageContext messages = context.getMessageContext();
        if (booking.getCheckinDate().before(today())) {
            messages.addMessage(new MessageBuilder().error().source("checkinDate").
                defaultText("Check in date must be a future date").build());
        } else if (!booking.getCheckinDate().before(booking.getCheckoutDate())) {
            messages.addMessage(new MessageBuilder().error().source("checkoutDate").
                defaultText("Check out date must be later than check in date").build());
        }
    }
}
    
In the example above, when a transition is triggered in a enterBookingDetails view-state that is editing a Booking model, Web Flow will invoke the validateEnterBookingDetails(Booking, ValidationContext) method automatically unless validation has been suppressed for that transition.
A Validator can also accept a Spring MVC Errors object, which is required for invoking existing Spring Validators.
Validators must be registered as Spring beans employing the naming convention ${model}Validator to be detected and invoked automatically. In the example above, Spring 2.5 classpath-scanning would detect the @Component and automatically register it as a bean with the namebookingValidator. Then, anytime the booking model needs to be validated, this bookingValidator instance would be invoked for you.

Default validate method

Validator class can also define a method called validate not associated (by convention) with any specific view-state.
@Component
public class BookingValidator {
    public void validate(Booking booking, ValidationContext context) {
        //...
    } 
}
    
In the above code sample the method validate will be called every time a Model of type Booking is validated (unless validation has been suppressed for that transition). If needed the default method can also be called in addition to an existing state-specific method. Consider the following example:
@Component
public class BookingValidator {
    public void validate(Booking booking, ValidationContext context) {
        //...
    }
    public void validateEnterBookingDetails(Booking booking, ValidationContext context) {
        //...
    }
}
    
In above code sample the method validateEnterBookingDetails will be called first. The default validate method will be called next.

ValidationContext

A ValidationContext allows you to obtain a MessageContext to record messages during validation. It also exposes information about the current user, such as the signaled userEvent and the current user's Principal identity. This information can be used to customize validation logic based on what button or link was activated in the UI, or who is authenticated. See the API Javadocs for ValidationContext for more information.

Suppressing validation

Use the validate attribute to suppress model validation for particular view events:

    
    

  
In this example, data binding will still occur on back but validation will be suppressed.

Executing view transitions

Define one or more transition elements to handle user events that may occur on the view. A transition may take the user to another view, or it may simply execute an action and re-render the current view. A transition may also request the rendering of parts of a view called "fragments" when handling an Ajax event. Finally, "global" transitions that are shared across all views may also be defined.
Implementing view transitions is illustrated in the following sections.

Transition actions

A view-state transition can execute one or more actions before executing. These actions may return an error result to prevent the transition from exiting the current view-state. If an error result occurs, the view will re-render and should display an appropriate message to the user.
If the transition action invokes a plain Java method, the invoked method may return false to prevent the transition from executing. This technique can be used to handle exceptions thrown by service-layer methods. The example below invokes an action that calls a service and handles an exceptional situation:

    

   
public class BookingAction {
   public boolean makeBooking(Booking booking, MessageContext context) {
       try {
           bookingService.make(booking);
           return true;
       } catch (RoomNotAvailableException e) {
           context.addMessage(new MessageBuilder().error().
               .defaultText("No room is available at this hotel").build());
           return false;
       }
   }
}
   

Note

When there is more than one action defined on a transition, if one returns an error result the remaining actions in the set will not be executed. If you need to ensure one transition action's result cannot impact the execution of another, define a single transition action that invokes a method that encapsulates all the action logic.

Global transitions

Use the flow's global-transitions element to create transitions that apply across all views. Global-transitions are often used to handle global menu links that are part of the layout.

    
    

   

Event handlers

From a view-state, transitions without targets can also be defined. Such transitions are called "event handlers":

    

   
These event handlers do not change the state of the flow. They simply execute their actions and re-render the current view or one or more fragments of the current view.

Rendering fragments

Use the render element within a transition to request partial re-rendering of the current view after handling the event:

    
                

   
The fragments attribute should reference the id(s) of the view element(s) you wish to re-render. Specify multiple elements to re-render by separating them with a comma delimiter.
Such partial rendering is often used with events signaled by Ajax to update a specific zone of the view.

Working with messages

Spring Web Flow's MessageContext is an API for recording messages during the course of flow executions. Plain text messages can be added to the context, as well as internationalized messages resolved by a Spring MessageSource. Messages are renderable by views and automatically survive flow execution redirects. Three distinct message severities are provided: infowarning, and error. In addition, a convenient MessageBuilder exists for fluently constructing messages.

Adding plain text messages

MessageContext context = ...
MessageBuilder builder = new MessageBuilder();
context.addMessage(builder.error().source("checkinDate")
    .defaultText("Check in date must be a future date").build());
context.addMessage(builder.warn().source("smoking")
    .defaultText("Smoking is bad for your health").build());
context.addMessage(builder.info()
    .defaultText("We have processed your reservation - thank you and enjoy your stay").build());
   

Adding internationalized messages

MessageContext context = ...
MessageBuilder builder = new MessageBuilder();
context.addMessage(builder.error().source("checkinDate").code("checkinDate.notFuture").build());
context.addMessage(builder.warn().source("smoking").code("notHealthy")
    .resolvableArg("smoking").build());   
context.addMessage(builder.info().code("reservationConfirmation").build());
   

Using message bundles

Internationalized messages are defined in message bundles accessed by a Spring MessageSource. To create a flow-specific message bundle, simply define messages.properties file(s) in your flow's directory. Create a default messages.properties file and a .properties file for each additional Locale you need to support.
#messages.properties
checkinDate=Check in date must be a future date
notHealthy={0} is bad for your health
reservationConfirmation=We have processed your reservation - thank you and enjoy your stay
   
From within a view or a flow, you may also access message resources using the resourceBundle EL variable:

   

Understanding system generated messages

There are several places where Web Flow itself will generate messages to display to the user. One important place this occurs is during view-to-model data binding. When a binding error occurs, such as a type conversion error, Web Flow will map that error to a message retrieved from your resource bundle automatically. To lookup the message to display, Web Flow tries resource keys that contain the binding error code and target property name.
As an example, consider a binding to a checkinDate property of a Booking object. Suppose the user typed in a alphabetic string. In this case, a type conversion error will be raised. Web Flow will map the 'typeMismatch' error code to a message by first querying your resource bundle for a message with the following key:
booking.checkinDate.typeMismatch
   
The first part of the key is the model class's short name. The second part of the key is the property name. The third part is the error code. This allows for the lookup of a unique message to display to the user when a binding fails on a model property. Such a message might say:
booking.checkinDate.typeMismatch=The check in date must be in the format yyyy-mm-dd.
   
If no such resource key can be found of that form, a more generic key will be tried. This key is simply the error code. The field name of the property is provided as a message argument.
typeMismatch=The {0} field is of the wrong type.
   

Displaying popups

Use the popup attribute to render a view in a modal popup dialog:

  
When using Web Flow with the Spring Javascript, no client side code is necessary for the popup to display. Web Flow will send a response to the client requesting a redirect to the view from a popup, and the client will honor the request.

View backtracking

By default, when you exit a view state and transition to a new view state, you can go back to the previous state using the browser back button. These view state history policies are configurable on a per-transition basis by using the history attribute.

Discarding history

Set the history attribute to discard to prevent backtracking to a view:

   

Invalidating history

Set the history attribute to invalidate to prevent backtracking to a view as well all previously displayed views:

   

Chapter 6. Executing actions

Introduction

This chapter shows you how to use the action-state element to control the execution of an action at a point within a flow. It will also show how to use the decision-state element to make a flow routing decision. Finally, several examples of invoking actions from the various points possible within a flow will be discussed.

Defining action states

Use the action-state element when you wish to invoke an action, then transition to another state based on the action's outcome:

    
    
    

        
The full example below illustrates a interview flow that uses the action-state above to determine if more answers are needed to complete the interview:


    
        
    

    
        
            
        
        
            
        
    
    
    
        
        
        
    

    
    

   

Defining decision states

Use the decision-state element as an alternative to the action-state to make a routing decision using a convenient if/else syntax. The example below shows the moreAnswersNeeded state above now implemented as a decision state instead of an action-state:

    

   

Action outcome event mappings

Actions often invoke methods on plain Java objects. When called from action-states and decision-states, these method return values can be used to drive state transitions. Since transitions are triggered by events, a method return value must first be mapped to an Event object. The following table describes how common return value types are mapped to Event objects:
Table 6.1. Action method return value to event id mappings
Method return typeMapped Event identifier expression
java.lang.Stringthe String value
java.lang.Booleanyes (for true), no (for false)
java.lang.Enumthe Enum name
any other typesuccess

This is illustrated in the example action state below, which invokes a method that returns a boolean value:

    
    
    

        

Action implementations

While writing action code as POJO logic is the most common, there are several other action implementation options. Sometimes you need to write action code that needs access to the flow context. You can always invoke a POJO and pass it the flowRequestContext as an EL variable. Alternatively, you may implement the Action interface or extend from the MultiAction base class. These options provide stronger type safety when you have a natural coupling between your action code and Spring Web Flow APIs. Examples of each of these approaches are shown below.

Invoking a POJO action

 
         
public class PojoAction {
    public String method(RequestContext context) {
        ... 
    }
}
   

Invoking a custom Action implementation

 
         
public class CustomAction implements Action {
    public Event execute(RequestContext context) {
        ... 
    }
}
   

Invoking a MultiAction implementation


 
         
public class CustomMultiAction extends MultiAction {
    public Event actionMethod1(RequestContext context) {
        ... 
    }

    public Event actionMethod2(RequestContext context) {
        ... 
    }

    ...
}
   

Action exceptions

Actions often invoke services that encapsulate complex business logic. These services may throw business exceptions that the action code should handle.

Handling a business exception with a POJO action

The following example invokes an action that catches a business exception, adds a error message to the context, and returns a result event identifier. The result is treated as a flow event which the calling flow can then respond to.
 
         
public class BookingAction {
   public String makeBooking(Booking booking, RequestContext context) {
       try {
           BookingConfirmation confirmation = bookingService.make(booking);
           context.getFlowScope().put("confirmation", confirmation);
           return "success";
       } catch (RoomNotAvailableException e) {
           context.addMessage(new MessageBuilder().error().
               .defaultText("No room is available at this hotel").build());
           return "error";
       }
   }
}
   

Handling a business exception with a MultiAction

The following example is functionally equivlant to the last, but implemented as a MultiAction instead of a POJO action. The MultiAction requires its action methods to be of the signature Event ${methodName}(RequestContext), providing stronger type safety, while a POJO action allows for more freedom.
 
         
public class BookingAction extends MultiAction {
   public Event makeBooking(RequestContext context) {
       try {
           Booking booking = (Booking) context.getFlowScope().get("booking");
           BookingConfirmation confirmation = bookingService.make(booking);
           context.getFlowScope().put("confirmation", confirmation);
           return success();
       } catch (RoomNotAvailableException e) {
           context.getMessageContext().addMessage(new MessageBuilder().error().
               .defaultText("No room is available at this hotel").build());
           return error();
       }
   }
}
   

Other Action execution examples

on-start

The following example shows an action that creates a new Booking object by invoking a method on a service:


    

    
        
    


   

on-entry

The following example shows a state entry action that sets the special fragments variable that causes the view-state to render a partial fragment of its view:

    
        
    

   

on-exit

The following example shows a state exit action that releases a lock on a record being edited:

    
        
    
    
        
    
    
        
    

   

on-end

The following example shows the equivalent object locking behavior using flow start and end actions:


    

    
        
    

    
        
            
        
    

    
        
    
    

   

on-render

The following example shows a render action that loads a list of hotels to display before the view is rendered:

    
        
    
    
        
    

   

on-transition

The following example shows a transition action adds a subflow outcome event attribute to a collection:

    
          
    

Named actions

The following example shows how to execute a chain of actions in an action-state. The name of each action becomes a qualifier for the action's result event.

    
        
    
    
        
    
    

   
In this example, the flow will transition to showResults when thingTwo completes successfully.

Streaming actions

Sometimes an Action needs to stream a custom response back to the client. An example might be a flow that renders a PDF document when handling a print event. This can be achieved by having the action stream the content then record "Response Complete" status on the ExternalContext. The responseComplete flag tells the pausing view-state not to render the response because another object has taken care of it.

    
        
    

   
public class PrintBoardingPassAction extends AbstractAction {
    public Event doExecute(RequestContext context) {
        // stream PDF content here...
        // - Access HttpServletResponse by calling context.getExternalContext().getNativeResponse();
        // - Mark response complete by calling context.getExternalContext().recordResponseComplete();
        return success();
    }
}
   
In this example, when the print event is raised the flow will call the printBoardingPassAction. The action will render the PDF then mark the response as complete.

Handling File Uploads

Another common task is to use Web Flow to handle multipart file uploads in combination with Spring MVC's MultipartResolver. Once the resolver is set up correctly as described here and the submitting HTML form is configured with enctype="multipart/form-data", you can easily handle the file upload in a transition action.

Note

The file upload example below below is not relevant when using Web Flow with JSF. See the section called “Handling File Uploads with JSF” for details of how to upload files using JSF.
Given a form such as:

 Select file:   
    

   
and a backing object for handling the upload such as:
package org.springframework.webflow.samples.booking;

import org.springframework.web.multipart.MultipartFile;

public class FileUploadHandler {
    
    private transient MultipartFile file;
    
    public void processFile() {
  //Do something with the MultipartFile here
    }

    public void setFile(MultipartFile file) {
        this.file = file;
    } 
}
   
you can process the upload using a transition action as in the following example:

    
    
        
    
    

   
The MultipartFile will be bound to the FileUploadHandler bean as part of the normal form binding process so that it will be available to process during the execution of the transition action.

Chapter 7. Flow Managed Persistence

Introduction

Most applications access data in some way. Many modify data shared by multiple users and therefore require transactional data access properties. They often transform relational data sets into domain objects to support application processing. Web Flow offers "flow managed persistence" where a flow can create, commit, and close a object persistence context for you. Web Flow integrates both Hibernate and JPA object persistence technologies.
Apart from flow-managed persistence, there is the pattern of fully encapsulating PersistenceContext management within the service layer of your application. In that case, the web layer does not get involved with persistence, instead it works entirely with detached objects that are passed to and returned by your service layer. This chapter will focus on the flow-managed persistence, exploring how and when to use this feature.

FlowScoped PersistenceContext

This pattern creates a PersistenceContext in flowScope on flow startup, uses that context for data access during the course of flow execution, and commits changes made to persistent entities at the end. This pattern provides isolation of intermediate edits by only committing changes to the database at the end of flow execution. This pattern is often used in conjunction with an optimistic locking strategy to protect the integrity of data modified in parallel by multiple users. To support saving and restarting the progress of a flow over an extended period of time, a durable store for flow state must be used. If a save and restart capability is not required, standard HTTP session-based storage of flow state is sufficient. In that case, session expiration or termination before commit could potentially result in changes being lost.
To use the FlowScoped PersistenceContext pattern, first mark your flow as a persistence-context:


    
    

Then configure the correct FlowExecutionListener to apply this pattern to your flow. If using Hibernate, register the HibernateFlowExecutionListener. If using JPA, register the JpaFlowExecutionListener.

    
        
    

 

    
    

To trigger a commit at the end, annotate your end-state with the commit attribute:



That is it. When your flow starts, the listener will handle allocating a new EntityManager in flowScope. Reference this EntityManager at anytime from within your flow by using the special persistenceContext variable. In addition, any data access that occurs using a Spring managed data access object will use this EntityManager automatically. Such data access operations should always execute non transactionally or in read-only transactions to maintain isolation of intermediate edits.

Flow Managed Persistence And Sub-Flows

A flow managed PersistenceContext is automatically extended (propagated) to subflows assuming the subflow also has the  variable. When a subflow re-uses the PersistenceContext started by its parent it ignores commit flags when an end state is reached thereby deferring the final decision (to commit or not) to its parent.

Chapter 8. Securing Flows

Introduction

Security is an important concept for any application. End users should not be able to access any portion of a site simply by guessing the URL. Areas of a site that are sensitive must ensure that only authorized requests are processed. Spring Security is a proven security platform that can integrate with your application at multiple levels. This section will focus on securing flow execution.

How do I secure a flow?

Securing flow execution is a three step process:
  • Configure Spring Security with authentication and authorization rules
  • Annotate the flow definition with the secured element to define the security rules
  • Add the SecurityFlowExecutionListener to process the security rules.

Each of these steps must be completed or else flow security rules will not be applied.

The secured element

The secured element designates that its containing element should apply the authorization check before fully entering. This may not occur more then once per stage of the flow execution that is secured.
Three phases of flow execution can be secured: flows, states and transitions. In each case the syntax for the secured element is identical. The secured element is located inside the element it is securing. For example, to secure a state the secured element occurs directly inside that state:

    
    ...

  

Security attributes

The attributes attribute is a comma separated list of Spring Security authorization attributes. Often, these are specific security roles. The attributes are compared against the user's granted attributes by a Spring Security access decision manager.

   
By default, a role based access decision manager is used to determine if the user is allowed access. This will need to be overridden if your application is not using authorization roles.

Matching type

There are two types of matching available: any and all. Any, allows access if at least one of the required security attributes is granted to the user. All, allows access only if each of the required security attributes are granted to the user.

   
This attribute is optional. If not defined, the default value is any.
The match attribute will only be respected if the default access decision manager is used.

The SecurityFlowExecutionListener

Defining security rules in the flow by themselves will not protect the flow execution. A SecurityFlowExecutionListener must also be defined in the webflow configuration and applied to the flow executor.

    
        
    



  
If access is denied to a portion of the application an AccessDeniedException will be thrown. This exception will later be caught by Spring Security and used to prompt the user to authenticate. It is important that this exception be allowed to travel up the execution stack uninhibited, otherwise the end user may not be prompted to authenticate.

Custom Access Decision Managers

If your application is using authorities that are not role based, you will need to configure a custom AccessDecisionManager. You can override the default decision manager by setting the accessDecisionManager property on the security listener. Please consult the Spring Security reference documentation to learn more about decision managers.

    

   

Configuring Spring Security

Spring Security has robust configuration options available. As every application and environment has its own security requirements, the Spring Security reference documentation is the best place to learn the available options.
Both the booking-faces and booking-mvc sample applications are configured to use Spring Security. Configuration is needed at both the Spring and web.xml levels.

Spring configuration

The Spring configuration defines http specifics (such as protected URLs and login/logout mechanics) and the authentication-provider. For the sample applications, a local authentication provider is configured.

      
    



    
    
        
        
        
        
    

   

web.xml Configuration

In the web.xml file, a filter is defined to intercept all requests. This filter will listen for login/logout requests and process them accordingly. It will also catch AccesDeniedExceptions and redirect the user to the login page.

    springSecurityFilterChain
    org.springframework.web.filter.DelegatingFilterProxy



    springSecurityFilterChain
    /*

   

Chapter 9. Flow Inheritance

Introduction

Flow inheritance allows one flow to inherit the configuration of another flow. Inheritance can occur at both the flow and state levels. A common use case is for a parent flow to define global transitions and exception handlers, then each child flow can inherit those settings.
In order for a parent flow to be found, it must be added to the flow-registry just like any other flow.

Is flow inheritance like Java inheritance?

Flow inheritance is similar to Java inheritance in that elements defined in a parent are exposed via the child, however, there are key differences.
A child flow cannot override an element from a parent flow. Similar elements between the parent and child flows will be merged. Unique elements in the parent flow will be added to the child.
A child flow can inherit from multiple parent flows. Java inheritance is limited to a single class.

Types of Flow Inheritance

Flow level inheritance

Flow level inheritance is defined by the parent attribute on the flow element. The attribute contains a comma separated list of flow identifiers to inherit from. The child flow will inherit from each parent in the order it is listed adding elements and content to the resulting flow. The resulting flow from the first merge will be considered the child in the second merge, and so on.

   

State level inheritance

State level inheritance is similar to flow level inheritance, except only one state inherits from the parent, instead of the entire flow.
Unlike flow inheritance, only a single parent is allowed. Additionally, the identifier of the flow state to inherit from must also be defined. The identifiers for the flow and the state within that flow are separated by a #.
The parent and child states must be of the same type. For instance a view-state cannot inherit from an end-state, only another view-state.

   

Abstract flows

Often parent flows are not designed to be executed directly. In order to protect these flows from running, they can be marked as abstract. If an abstract flow attempts to run, a FlowBuilderException will be thrown.

  

Inheritance Algorithm

When a child flow inherits from it's parent, essentially what happens is that the parent and child are merged together to create a new flow. There are rules for every element in the Web Flow definition language that govern how that particular element is merged.
There are two types of elements: mergeable and non-mergeable. Mergeable elements will always attempt to merge together if the elements are similar. Non-mergeable elements in a parent or child flow will always be contained in the resulting flow intact. They will not be modified as part of the merge process.

Note

Paths to external resources in the parent flow should be absolute. Relative paths will break when the two flows are merged unless the parent and child flow are in the same directory. Once merged, all relative paths in the parent flow will become relative to the child flow.

Mergeable Elements

If the elements are of the same type and their keyed attribute are identical, the content of the parent element will be merged with the child element. The merge algorithm will continue to merge each sub-element of the merging parent and child. Otherwise the parent element is added as a new element to the child.
In most cases, elements from a parent flow that are added will be added after elements in the child flow. Exceptions to this rule include action elements (evaluate, render and set) which will be added at the beginning. This allows for the results of parent actions to be used by child actions.
Mergeable elements are:
  • action-state: id
  • attribute: name
  • decision-state: id
  • end-state: id
  • flow: always merges
  • if: test
  • on-end: always merges
  • on-entry: always merges
  • on-exit: always merges
  • on-render: always merges
  • on-start: always merges
  • input: name
  • output: name
  • secured: attributes
  • subflow-state: id
  • transition: on and on-exception
  • view-state: id

Non-mergeable Elements

Non-mergeable elements are:
  • bean-import
  • evaluate
  • exception-handler
  • persistence-context
  • render
  • set
  • var

Chapter 10. System Setup

Introduction

This chapter shows you how to setup the Web Flow system for use in any web environment.

webflow-config.xsd

Web Flow provides a Spring schema that allows you to configure the system. To use this schema, include it in one of your infrastructure-layer beans files:
  

    
 

  

Basic system configuration

The next section shows the minimal configuration required to set up the Web Flow system in your application.

FlowRegistry

Register your flows in a FlowRegistry:

    

   

FlowExecutor

Deploy a FlowExecutor, the central service for executing flows:

   
See the Spring MVC and Spring Faces sections of this guide on how to integrate the Web Flow system with the MVC and JSF environment, respectively.

flow-registry options

This section explores flow-registry configuration options.

Specifying flow locations

Use the location element to specify paths to flow definitions to register. By default, flows will be assigned registry identifiers equal to their filenames minus the file extension, unless a registry bath path is defined.

   

Assigning custom flow identifiers

Specify an id to assign a custom registry identifier to a flow:

   

Assigning flow meta-attributes

Use the flow-definition-attributes element to assign custom meta-attributes to a registered flow:

    
        
    

   

Registering flows using a location pattern

Use the flow-location-patterns element to register flows that match a specific resource location pattern:

   

Flow location base path

Use the base-path attribute to define a base location for all flows in the application. All flow locations are then relative to the base path. The base path can be a resource path such as '/WEB-INF' or a location on the classpath like 'classpath:org/springframework/webflow/samples'.

    

   
With a base path defined, the algorithm that assigns flow identifiers changes slightly. Flows will now be assigned registry identifiers equal to the the path segment between their base path and file name. For example, if a flow definition is located at '/WEB-INF/hotels/booking/booking-flow.xml' and the base path is '/WEB-INF' the remaining path to this flow is 'hotels/booking' which becomes the flow id.

Directory per flow definition

Recall it is a best practice to package each flow definition in a unique directory. This improves modularity, allowing dependent resources to be packaged with the flow definition. It also prevents two flows from having the same identifiers when using the convention.
If no base path is not specified or if the flow definition is directly on the base path, flow id assignment from the filename (minus the extension) is used. For example, if a flow definition file is 'booking.xml', the flow identifier is simply 'booking'.
Location patterns are particularly powerful when combined with a registry base path. Instead of the flow identifiers becoming '*-flow', they will be based on the directory path. For example:

    

   
In the above example, suppose you had flows located in /user/login/user/registration/hotels/booking, and /flights/booking directories within WEB-INF, you'd end up with flow ids of user/loginuser/registrationhotels/booking, and flights/booking, respectively.

Configuring FlowRegistry hierarchies

Use the parent attribute to link two flow registries together in a hierarchy. When the child registry is queried, if it cannot find the requested flow it will delegate to its parent.


    




    

   

Configuring custom FlowBuilder services

Use the flow-builder-services attribute to customize the services and settings used to build flows in a flow-registry. If no flow-builder-services tag is specified, the default service implementations are used. When the tag is defined, you only need to reference the services you want to customize.

    



   
The configurable services are the conversion-serviceexpression-parser, and view-factory-creator. These services are configured by referencing custom beans you define. For example:





   

conversion-service

Use the conversion-service attribute to customize the ConversionService used by the Web Flow system. Type conversion is used to convert from one type to another when required during flow execution such as when processing request parameters, invoking actions, and so on. Many common object types such as numbers, classes, and enums are supported. However you'll probably need to provide your own type conversion and formatting logic for custom data types. Please read the section called “Performing type conversion” for important information on how to provide custom type conversion logic.

expression-parser

Use the expression-parser attribute to customize the ExpressionParser used by the Web Flow system. The default ExpressionParser uses the Unified EL if available on the classpath, otherwise OGNL is used.

view-factory-creator

Use the view-factory-creator attribute to customize the ViewFactoryCreator used by the Web Flow system. The default ViewFactoryCreator produces Spring MVC ViewFactories capable of rendering JSP, Velocity, and Freemarker views.
The configurable settings are development. These settings are global configuration attributes that can be applied during the flow construction process.

development

Set this to true to switch on flow development mode. Development mode switches on hot-reloading of flow definition changes, including changes to dependent flow resources such as message bundles.

flow-executor options

This section explores flow-executor configuration options.

Attaching flow execution listeners

Use the flow-execution-listeners element to register listeners that observe the lifecycle of flow executions:

    
    

   
You may also configure a listener to observe only certain flows:

   

Tuning FlowExecution persistence

Use the flow-execution-repository element to tune flow execution persistence settings:

    

   

max-executions

Tune the max-executions attribute to place a cap on the number of flow executions that can be created per user session. When the maximum number of executions is exceeded, the oldest execution is removed.

Note

The max-executions attribute is per user session, i.e. it works across instances of any flow definition.

max-execution-snapshots

Tune the max-execution-snapshots attribute to place a cap on the number of history snapshots that can be taken per flow execution. To disable snapshotting, set this value to 0. To enable an unlimited number of snapshots, set this value to -1.

Note

History snapshots enable browser back button support. When snapshotting is disabled pressing the browser back button will not work. It will result in using an execution key that points to a snapshot that has not be recorded.

Chapter 11. Spring MVC Integration

Introduction

This chapter shows how to integrate Web Flow into a Spring MVC web application. The booking-mvc sample application is a good reference for Spring MVC with Web Flow. This application is a simplified travel site that allows users to search for and book hotel rooms.

Configuring web.xml

The first step to using Spring MVC is to configure the DispatcherServlet in web.xml. You typically do this once per web application.
The example below maps all requests that begin with /spring/ to the DispatcherServlet. An init-param is used to provide the contextConfigLocation. This is the configuration file for the web application.

    Spring MVC Dispatcher Servlet
    org.springframework.web.servlet.DispatcherServlet
    
        contextConfigLocation
        /WEB-INF/web-application-config.xml
    

 

    Spring MVC Dispatcher Servlet
    /spring/*

Dispatching to flows

The DispatcherServlet maps requests for application resources to handlers. A flow is one type of handler.

Registering the FlowHandlerAdapter

The first step to dispatching requests to flows is to enable flow handling within Spring MVC. To this, install the FlowHandlerAdapter:


    

   

Defining flow mappings

Once flow handling is enabled, the next step is to map specific application resources to your flows. The simplest way to do this is to define a FlowHandlerMapping:
  

    
    

   
Configuring this mapping allows the Dispatcher to map application resource paths to flows in a flow registry. For example, accessing the resource path /hotels/booking would result in a registry query for the flow with id hotels/booking. If a flow is found with that id, that flow will handle the request. If no flow is found, the next handler mapping in the Dispatcher's ordered chain will be queried or a "noHandlerFound" response will be returned.

Flow handling workflow

When a valid flow mapping is found, the FlowHandlerAdapter figures out whether to start a new execution of that flow or resume an existing execution based on information present the HTTP request. There are a number of defaults related to starting and resuming flow executions the adapter employs:
  • HTTP request parameters are made available in the input map of all starting flow executions.
  • When a flow execution ends without sending a final response, the default handler will attempt to start a new execution in the same request.
  • Unhandled exceptions are propagated to the Dispatcher unless the exception is a NoSuchFlowExecutionException. The default handler will attempt to recover from a NoSuchFlowExecutionException by starting over a new execution.
Consult the API documentation for FlowHandlerAdapter for more information. You may override these defaults by subclassing or by implementing your own FlowHandler, discussed in the next section.

Implementing custom FlowHandlers

FlowHandler is the extension point that can be used to customize how flows are executed in a HTTP servlet environment. A FlowHandler is used by the FlowHandlerAdapter and is responsible for:
  • Returning the id of a flow definition to execute
  • Creating the input to pass new executions of that flow as they are started
  • Handling outcomes returned by executions of that flow as they end
  • Handling any exceptions thrown by executions of that flow as they occur
These responsibilities are illustrated in the definition of the org.springframework.mvc.servlet.FlowHandler interface:
public interface FlowHandler {

    public String getFlowId();

    public MutableAttributeMap createExecutionInputMap(HttpServletRequest request);

    public String handleExecutionOutcome(FlowExecutionOutcome outcome,
        HttpServletRequest request, HttpServletResponse response);

    public String handleException(FlowException e,
        HttpServletRequest request, HttpServletResponse response);
}    
  
To implement a FlowHandler, subclass AbstractFlowHandler. All these operations are optional, and if not implemented the defaults will apply. You only need to override the methods that you need. Specifically:
  • Override getFlowId(HttpServletRequest) when the id of your flow cannot be directly derived from the HTTP request. By default, the id of the flow to execute is derived from the pathInfo portion of the request URI. For example, http://localhost/app/hotels/booking?hotelId=1 results in a flow id of hotels/booking by default.
  • Override createExecutionInputMap(HttpServletRequest) when you need fine-grained control over extracting flow input parameters from the HttpServletRequest. By default, all request parameters are treated as flow input parameters.
  • Override handleExecutionOutcome when you need to handle specific flow execution outcomes in a custom manner. The default behavior sends a redirect to the ended flow's URL to restart a new execution of the flow.
  • Override handleException when you need fine-grained control over unhandled flow exceptions. The default behavior attempts to restart the flow when a client attempts to access an ended or expired flow execution. Any other exception is rethrown to the Spring MVC ExceptionResolver infrastructure by default.

Example FlowHandler

A common interaction pattern between Spring MVC And Web Flow is for a Flow to redirect to a @Controller when it ends. FlowHandlers allow this to be done without coupling the flow definition itself with a specific controller URL. An example FlowHandler that redirects to a Spring MVC Controller is shown below:
public class BookingFlowHandler extends AbstractFlowHandler {
    public String handleExecutionOutcome(FlowExecutionOutcome outcome,
                                         HttpServletRequest request, HttpServletResponse response) {
        if (outcome.getId().equals("bookingConfirmed")) {
            return "/booking/show?bookingId=" + outcome.getOutput().get("bookingId");
        } else {
            return "/hotels/index";
        }
    }
}
   
Since this handler only needs to handle flow execution outcomes in a custom manner, nothing else is overridden. The bookingConfirmed outcome will result in a redirect to show the new booking. Any other outcome will redirect back to the hotels index page.

Deploying a custom FlowHandler

To install a custom FlowHandler, simply deploy it as a bean. The bean name must match the id of the flow the handler should apply to.

   
With this configuration, accessing the resource /hotels/booking will launch the hotels/booking flow using the custom BookingFlowHandler. When the booking flow ends, the FlowHandler will process the flow execution outcome and redirect to the appropriate controller.

FlowHandler Redirects

A FlowHandler handling a FlowExecutionOutcome or FlowException returns a String to indicate the resource to redirect to after handling. In the previous example, the BookingFlowHandler redirects to the booking/show resource URI for bookingConfirmed outcomes, and thehotels/index resource URI for all other outcomes.
By default, returned resource locations are relative to the current servlet mapping. This allows for a flow handler to redirect to other Controllers in the application using relative paths. In addition, explicit redirect prefixes are supported for cases where more control is needed.
The explicit redirect prefixes supported are:
  • servletRelative: - redirect to a resource relative to the current servlet
  • contextRelative: - redirect to a resource relative to the current web application context path
  • serverRelative: - redirect to a resource relative to the server root
  • http:// or https:// - redirect to a fully-qualified resource URI
These same redirect prefixes are also supported within a flow definition when using the externalRedirect: directive in conjunction with a view-state or end-state; for example, view="externalRedirect:http://springframework.org"

View Resolution

Web Flow 2 maps selected view identifiers to files located within the flow's working directory unless otherwise specified. For existing Spring MVC + Web Flow applications, an external ViewResolver is likely already handling this mapping for you. Therefore, to continue using that resolver and to avoid having to change how your existing flow views are packaged, configure Web Flow as follows:

    





    

  
The MvcViewFactoryCreator is the factory that allows you to configure how the Spring MVC view system is used inside Spring Web Flow. Use it to configure existing ViewResolvers, as well as other services such as a custom MessageCodesResolver. You may also enable data binding use Spring MVC's native BeanWrapper by setting the useSpringBinding flag to true. This is an alternative to using OGNL or the Unified EL for view-to-model data binding. See the JavaDoc API of this class for more information.

Signaling an event from a View

When a flow enters a view-state it pauses, redirects the user to its execution URL, and waits for a user event to resume. Events are generally signaled by activating buttons, links, or other user interface commands. How events are decoded server-side is specific to the view technology in use. This section shows how to trigger events from HTML-based views generated by templating engines such as JSP, Velocity, or Freemarker.

Using a named HTML button to signal an event

The example below shows two buttons on the same form that signal proceed and cancel events when clicked, respectively.

  
   
When a button is pressed Web Flow finds a request parameter name beginning with _eventId_ and treats the remaining substring as the event id. So in this example, submitting _eventId_proceed becomes proceed. This style should be considered when there are several different events that can be signaled from the same form.

Using a hidden HTML form parameter to signal an event

The example below shows a form that signals the proceed event when submitted:

 
   
Here, Web Flow simply detects the special _eventId parameter and uses its value as the event id. This style should only be considered when there is one event that can be signaled on the form.

Using a HTML link to signal an event

The example below shows a link that signals the cancel event when activated:
Cancel  
   
Firing an event results in a HTTP request being sent back to the server. On the server-side, the flow handles decoding the event from within its current view-state. How this decoding process works is specific to the view implementation. Recall a Spring MVC view implementation simply looks for a request parameter named _eventId. If no _eventId parameter is found, the view will look for a parameter that starts with _eventId_ and will use the remaining substring as the event id. If neither cases exist, no flow event is triggered.

Embedding A Flow On A Page

By default when a flow enters a view state, it executes a client-side redirect before rendering the view. This approach is known as POST-REDIRECT-GET. It has the advantage of separating the form processing for one view from the rendering of the next view. As a result the browser Back and Refresh buttons work seamlessly without causing any browser warnings.
Normally the client-side redirect is transparent from a user's perspective. However, there are situations where POST-REDIRECT-GET may not bring the same benefits. For example a flow may be embedded on a page and driven via Ajax requests refreshing only the area of the page that belongs to the flow. Not only is it unnecessary to use client-side redirects in this case, it is also not the desired behavior with regards to keeping the surrounding content of the page intact.
The the section called “Handling Ajax Requests” explains how to do partial rendering during Ajax requests. The focus of this section is to explain how to control flow execution redirect behavior during Ajax requests. To indicate a flow should execute in "page embedded" mode all you need to do is append an extra parameter when launching the flow:
/hotels/booking?mode=embedded
When launched in "page embedded" mode a flow will not issue flow execution redirects during Ajax requests. The mode=embedded parameter only needs to be passed when launching the flow. Your only other concern is to use Ajax requests and to render only the content required to update the portion of the page displaying the flow.

Embedded Mode Vs Default Redirect Behavior

By default Web Flow does a client-side redirect upon entering every view state. However if you remain in the same view state -- for example a transition without a "to" attribute -- during an Ajax request there will not be a client-side redirect. This behavior should be quite familiar to Spring Web Flow 2 users. It is appropriate for a top-level flow that supports the browser back button while still taking advantage of Ajax and partial rendering for use cases where you remain in the same view such as form validation, paging trough search results, and others. However transitions to a new view state are always followed with a client-side redirect. That makes it impossible to embed a flow on a page or within a modal dialog and execute more than one view state without causing a full-page refresh. Hence if your use case requires embedding a flow you can launch it in "embedded" mode.

Embedded Flow Examples

If you'd like to see examples of a flow embedded on a page and within a modal dialog please refer to the webflow-showcase project. You can check out the source code locally, build it as you would a Maven project, and import it into Eclipse:
cd some-directory
svn co https://src.springframework.org/svn/spring-samples/webflow-showcase
cd webflow-showcase
mvn package
# import into Eclipse

Chapter 12. Spring JavaScript Quick Reference

Introduction

Spring Javascript (spring-js) is a lightweight abstraction over common JavaScript toolkits such as Dojo. It aims to provide a common client-side programming model for progressively enhancing a web page with rich widget behavior and Ajax remoting.
Use of the Spring JS API is demonstrated in the the Spring MVC + Web Flow version of the Spring Travel reference application. In addition, the JSF components provided as part of the Spring Faces library build on Spring.js.

Serving Javascript Resources

Spring JS provides a generic ResourceServlet to serve web resources such as JavaScript and CSS files from jar files, as well as the webapp root directory. This servlet provides a convenient way to serve Spring.js files to your pages. To deploy this servlet, declare the following in web.xml:


    Resource Servlet
    org.springframework.js.resource.ResourceServlet

        


    Resource Servlet
    /resources/*

        
Note that starting with version 3.0.4, the Spring Framework includes a replacement for the ResourceServlet (see the Spring Framework documentation). With the new element resource requests (.js, .css) are handled by the DispatcherSevlet without the need for a separate ResourceServlet. Here is the relevant portion of the Spring MVC configuration in the mvc-booking sample:


 

 

 ...
 
 

        
This incoming maps requests for /resources to resources found under /META-INF/web-resources on the classpath. That's where Spring JavaScript resources are bundled. However, you can modify the location attribute in the above configuration in order to serve resources from any classpath or web application relative location.
Note that the full resource URL depends on how your DispatcherServlet is mapped. In the mvc-booking sample we've chosen to map it with the default servlet mapping '/':

 Spring MVC Dispatcher Servlet
 org.springframework.web.servlet.DispatcherServlet



 Spring MVC Dispatcher Servlet
 /


        
That means the full URL to load Spring.js is /myapp/resources/spring/Spring.js. If your DispatcherServlet was instead mapped to /main/* then the full URL would be /myapp/main/resources/spring/Spring.js.
When using of the default servlet mapping it is also recommended to add this to your Spring MVC configuration, which ensures that any resource requests not handled by your Spring MVC mappings will be delegated back to the Servlet container.


 ...

 
 
 

        

Including Spring Javascript in a Page

Spring JS is designed such that an implementation of its API can be built for any of the popular Javascript toolkits. The initial implementation of Spring.js builds on the Dojo toolkit.
Using Spring Javascript in a page requires including the underlying toolkit as normal, the Spring.js base interface file, and the Spring-(library implementation).js file for the underlying toolkit. As an example, the following includes obtain the Dojo implementation of Spring.js using the ResourceServlet:



        
When using the widget system of an underlying library, typically you must also include some CSS resources to obtain the desired look and feel. For the booking-mvc reference application, Dojo's tundra.css is included:
" />
        

Spring Javascript Decorations

A central concept in Spring Javascript is the notion of applying decorations to existing DOM nodes. This technique is used to progressively enhance a web page such that the page will still be functional in a less capable browser. The addDecoration method is used to apply decorations.
The following example illustrates enhancing a Spring MVC  tag with rich suggestion behavior:


        
The ElementDecoration is used to apply rich widget behavior to an existing DOM node. This decoration type does not aim to completely hide the underlying toolkit, so the toolkit's native widget type and attributes are used directly. This approach allows you to use a common decoration model to integrate any widget from the underlying toolkit in a consistent manner. See the booking-mvc reference application for more examples of applying decorations to do things from suggestions to client-side validation.
When using the ElementDecoration to apply widgets that have rich validation behavior, a common need is to prevent the form from being submitted to the server until validation passes. This can be done with the ValidateAllDecoration:


        
This decorates the "Proceed" button with a special onclick event handler that fires the client side validators and does not allow the form to submit until they pass successfully.
An AjaxEventDecoration applies a client-side event listener that fires a remote Ajax request to the server. It also auto-registers a callback function to link in the response:
Previous

        
This decorates the onclick event of the "Previous Results" link with an Ajax call, passing along a special parameter that specifies the fragment to be re-rendered in the response. Note that this link would still be fully functional if Javascript was unavailable in the client. (See the section called “Handling Ajax Requests” for details on how this request is handled on the server.)
It is also possible to apply more than one decoration to an element. The following example shows a button being decorated with Ajax and validate-all submit suppression:
  

        
It is also possible to apply a decoration to multiple elements in a single statement using Dojo's query API. The following example decorates a set of checkbox elements as Dojo Checkbox widgets:

Handling Ajax Requests

Spring Javascript's client-side Ajax response handling is built upon the notion of receiving "fragments" back from the server. These fragments are just standard HTML that is meant to replace portions of the existing page. The key piece needed on the server is a way to determine which pieces of a full response need to be pulled out for partial rendering.
In order to be able to render partial fragments of a full response, the full response must be built using a templating technology that allows the use of composition for constructing the response, and for the member parts of the composition to be referenced and rendered individually. Spring Javascript provides some simple Spring MVC extensions that make use of Tiles to achieve this. The same technique could theoretically be used with any templating system supporting composition.
Spring Javascript's Ajax remoting functionality is built upon the notion that the core handling code for an Ajax request should not differ from a standard browser request, thus no special knowledge of an Ajax request is needed directly in the code and the same hanlder can be used for both styles of request.

Providing a Library-Specific AjaxHandler

The key interface for integrating various Ajax libraries with the Ajax-aware behavior of Web Flow (such as not redirecting for a partial page update) is org.springframework.js.AjaxHandler. A SpringJavascriptAjaxHandler is configured by default that is able to detect an Ajax request submitted via the Spring JS client-side API and can respond appropriately in the case where a redirect is required. In order to integrate a different Ajax library (be it a pure JavaScript library, or a higher-level abstraction such as an Ajax-capable JSF component library), a customAjaxHandler can be injected into the FlowHandlerAdapter or FlowController.

Handling Ajax Requests with Spring MVC Controllers

In order to handle Ajax requests with Spring MVC controllers, all that is needed is the configuration of the provided Spring MVC extensions in your Spring application context for rendering the partial response (note that these extensions require the use of Tiles for templating):

    

            
This configures the AjaxUrlBasedViewResolver which in turn interprets Ajax requests and creates FlowAjaxTilesView objects to handle rendering of the appropriate fragments. Note that FlowAjaxTilesView is capable of handling the rendering for both Web Flow and pure Spring MVC requests. The fragments correspond to individual attributes of a Tiles view definition. For example, take the following Tiles view definition:

    



    
    

            
An Ajax request could specify the "body", "hotelSearchForm" or "bookingsTable" to be rendered as fragments in the request.

Handling Ajax Requests with Spring MVC + Spring Web Flow

Spring Web Flow handles the optional rendering of fragments directly in the flow definition language through use of the render element. The benefit of this approach is that the selection of fragments is completely decoupled from client-side code, such that no special parameters need to be passed with the request the way they currently must be with the pure Spring MVC controller approach. For example, if you wanted to render the "hotelSearchForm" fragment from the previous example Tiles view into a rich Javascript popup:

    
        
    
    
        
    
                
            

Chapter 13. JSF Integration

Introduction

Spring Web Flow provides a JSF integration that simplifies using JSF with Spring. It lets you use the JSF UI Component Model with Spring MVC and Spring Web Flow controllers. Along with the JSF integration Spring Web Flow provides a small Facelets component library (called Spring Faces) for use in JSF 1.2 environments and a Spring Security tag library for use in both JSF 1.2 and JSF 2.0 environments (see the section called “Using the Spring Security Facelets Tag Library” for more details).
Starting with version 2.2 the JSF integration in Web Flow supports JSF 2.0 including Sun Mojarra and Apache MyFaces runtime environments. Please, note however that JSF 2 partial state saving is not yet supported with Apache MyFaces and needs to be disabled with thejavax.faces.PARTIAL_STATE_SAVING context parameter in web.xml.
Also note that the Spring Faces component library, which provides Ajax and client-side validation capabilities is for JSF 1.2 environments only and will not be upgraded to JSF 2.0. Applications are encouraged to use 3rd party JSF 2 component libraries such as PrimeFaces and RichFaces. The swf-booking-faces sample in the Spring Web Flow distribution for example is built with JSF 2 and PrimeFaces components.
Spring Web Flow also supports using JSF in a portlet environment. Spring Web Flow's portlet integration supports Portlets API 2.0 and JSF 1.2 only. Currently JSF 2 is not supported in combination with portlets. See Chapter 14, Portlet Integration for more on Spring Web Flow's portlet integration.

JSF Integration For Spring Developers

Spring Web Flow complements the strengths of JSF, its component model, and provides more sophisticated state management and navigation. In addition you have the ability to use Spring MVC @Controller or flow definitions as controllers in the web layer.
JSF applications using Spring Web Flow applications gain benefits in the following areas:
  1. Managed bean facility
  2. Scope management
  3. Event handling
  4. Navigation
  5. Modularization and packaging of views
  6. Cleaner URLs
  7. Model-level validation
  8. Progressivy-enhancement sytle client-side validation
  9. Progressive-enhancement style Ajax requests with partial page updates
Using these features significantly reduce the amount of configuration required in faces-config.xml. They provide a cleaner separation between the view and controller layers along with better modularization of application functionals. These features are detailed in the sections to follow. The majority of these features build on the flow definition language of Spring Web Flow. Therefore it is assumed that you have an understanding of the foundations presented in Chapter 3, Defining Flows.

Configuring web.xml

The first step is to route requests to the DispatcherServlet in the web.xml file. In this example, we map all URLs that begin with /spring/ to the servlet. The servlet needs to be configured. An init-param is used in the servlet to pass the contextConfigLocation. This is the location of the Spring configuration for your web application.

    Spring MVC Dispatcher Servlet
    org.springframework.web.servlet.DispatcherServlet
    
        contextConfigLocation
        /WEB-INF/web-application-config.xml
    
    1

    

    Spring MVC Dispatcher Servlet
    /spring/*

        
In order for JSF to bootstrap correctly, the FacesServlet must be configured in web.xml as it normally would even though you generally will not need to route requests through it at all when using JSF with Spring Web Flow.


    Faces Servlet
    javax.faces.webapp.FacesServlet
    1

    


    Faces Servlet
    *.faces

        
The use of Facelets instead of JSP typically requires this in web.xml:
!-- Use JSF view templates saved as *.xhtml, for use with Facelets -->

    javax.faces.DEFAULT_SUFFIX
    .xhtml

        

Configuring web.xml in JSF 1.2

When using the JSF 1.2 Spring Faces component library, you also need to configure a servlet for serving CSS and JavaScript resources. This servlet must be mapped to /resources/* in order for the URL's rendered by the components to function correctly.


    Resource Servlet
    org.springframework.js.resource.ResourceServlet
    0

        


    Resource Servlet
    /resources/*

        
For optimal page-loading performance use the Spring Faces components includeStyles and includeScripts. These components will eagerly load the necessary CSS stylesheets and JavaScript files at the position they are placed in your JSF view template. In accordance with the recommendations of the Yahoo Performance Guildlines, these two tags should be placed in the head section of any page that uses the Spring Faces components. For example:
 




 
 Hotel Booking Sample Application
 
 
 
 
 

...


  
This shows the opening of a typical Facelets XHTML layout template that uses these components to force the loading of the needed CSS and JavaScript resources at the ideal position.
The includeStyles component includes the necessary resources for the Dojo widget theme. By default, it includes the resources for the "tundra" theme. An alternate theme may be selected by setting the optional "theme" and "themePath" attributes on the includeStyles component. For example:
 


  
will try to load a CSS stylesheet at "/styles/foobar/foobar.css" using the Spring JavaScript ResourceServlet.

Configuring Web Flow for use with JSF

This section explains how to configure Web Flow with JSF. The next section provides more details specific to using Web Flow with JSF 2. The following is sample configuration for Web Flow and JSF:


    
    
        
            
        
    
 
    
    
        
    

    
    

    
     


        
The main points are the installation of a FlowFacesContextLifecycleListener that manages a single FacesContext for the duration of Web Flow request and the use of the flow-builder-services element from the faces custom namespace to configure rendering for a JSF environment.
See the swf-booking-faces reference application in the distribution for a complete working example.

Configuring Spring MVC for JSF 2

In a JSF 2 environment you'll also need this Spring MVC related configuration:


    
    
    
        
    


        
The resources custom namespace element delegates JSF 2 resource requests to the JSF 2 resource API. The JsfFlowHandlerAdapter is a replacement for the FlowHandlerAdapter normally used with Web Flow. This adapter initializes itself with a JsfAjaxHandler instead of theSpringJavaSciprtAjaxHandler previously used with Spring Faces components.

Configuring faces-config.xml

In JSF 1.2 you need to provide the below configuration in faces-config.xml in order to use Facelets. If you are using JSP and not using the Spring Faces components, you do not need to add anything to your faces-config.xml

    
        
        com.sun.facelets.FaceletViewHandler  
    

        
In JSF 2.0 your faces-config.xml should use the faces-config schema version 2.0. Also you should remove the FaceletViewHandler shown above (if it is present) as Facelets are now the default rendering technology in JSF 2.



        

Replacing the JSF Managed Bean Facility

When using JSF with Spring Web Flow you can completely replace the JSF managed bean facility with a combination of Web Flow managed variables and Spring managed beans. It gives you a good deal more control over the lifecycle of your managed objects with well-defined hooks for initialization and execution of your domain model. Additionally, since you are presumably already using Spring for your business layer, it reduces the conceptual overhead of having to maintain two different managed bean models.
In doing pure JSF development, you will quickly find that request scope is not long-lived enough for storing conversational model objects that drive complex event-driven views. In JSF 1.2 the only available option is to begin putting things into session scope, with the extra burden of needing to clean the objects up before progressing to another view or functional area of the application. What is really needed is a managed scope that is somewhere between request and session scope. JSF 2 provides flash and view scopes that can be accessed programmatically via UIViewRoot.getViewMap(). Spring Web Flow provides access to flash, view, flow, and conversation scopes. These scopes are seamlessly integrated through JSF variable resolvers and work the same in JSF 1.2 and in JSF 2.0 applications.

Using Flow Variables

The easiest and most natural way to declare and manage the model is through the use of flow variables. You can declare these variables at the beginning of the flow:

            
and then reference this variable in one of the flow's JSF view templates through EL:

            
Note that you do not need to prefix the variable with its scope when referencing it from the template (though you can do so if you need to be more specific). As with standard JSF beans, all available scopes will be searched for a matching variable, so you could change the scope of the variable in your flow definition without having to modify the EL expressions that reference it.
You can also define view instance variables that are scoped to the current view and get cleaned up automatically upon transitioning to another view. This is quite useful with JSF as views are often constructed to handle multiple in-page events across many requests before transitioning to another view.
To define a view instance variable, you can use the var element inside a view-state definition:
 
     

            

Using Scoped Spring Beans

Though defining autowired flow instance variables provides nice modularization and readability, occasions may arise where you want to utilize the other capabilities of the Spring container such as AOP. In these cases, you can define a bean in your Spring ApplicationContext and give it a specific web flow scope:

            
The major difference with this approach is that the bean will not be fully initialized until it is first accessed via an EL expression. This sort of lazy instantiation via EL is quite similar to how JSF managed beans are typically allocated.

Manipulating The Model

The need to initialize the model before view rendering (such as by loading persistent entities from a database) is quite common, but JSF by itself does not provide any convenient hooks for such initialization. The flow definition language provides a natural facility for this through its Actions . Spring Web Flow provides some extra conveniences for converting the outcome of an action into a JSF-specific data structure. For example:
 

    

            
This will take the result of the bookingService.findBookings method an wrap it in a custom JSF DataModel so that the list can be used in a standard JSF DataTable component:
 

    
        Name
        #{booking.hotel.name}
                       
    
    Confirmation number
        #{booking.id}
        
    
        Action
        
    

            

Data Model Implementations

In the example above result-type="dataModel" results in the wrapping of List with custom DataModel type. The custom DataModel provides extra conveniences such as being serializable for storage beyond request scope as well as access to the currently selected row in EL expressions. For example, on postback from a view where the action event was fired by a component within a DataTable, you can take action on the selected row's model instance:

                

            
Spring Web Flow provides two custom DataModel types: OneSelectionTrackingListDataModel and ManySelectionTrackingListDataModel. As the names indicate they keep track of one or multiple selected rows. This is done with the help of a SelectionTrackingActionListenerlistener, which responds to JSF action events and invokes the appopriate methods on the SelectinAware data models to record the currently clicked row.
To understand how this is configured, keep in mind the FacesConversionService registers a DataModelConverter against the alias "dataModel" on startup. When result-type="dataModel" is used in a flow definition it causes the DataModelConverter to be used. The converter then wraps the given List with an instance of OneSelectionTrackingListDataModel. To use the ManySelectionTrackingListDataModel you will need to register your own custom converter.

Handling JSF Events With Spring Web Flow

Spring Web Flow allows you to handle JSF action events in a decoupled way, requiring no direct dependencies in your Java code on JSF API's. In fact, these events can often be handled completely in the flow definiton language without requiring any custom Java action code at all. This allows for a more agile development process since the artifacts being manipulated in wiring up events (JSF view templates and SWF flow definitions) are instantly refreshable without requiring a build and re-deploy of the whole application.

Handling JSF In-page Action Events

A simple but common case in JSF is the need to signal an event that causes manipulation of the model in some way and then redisplays the same view to reflect the changed state of the model. The flow definition language has special support for this in the transition element.
A good example of this is a table of paged list results. Suppose you want to be able to load and display only a portion of a large result list, and allow the user to page through the results. The initial view-state definition to load and display the list would be:
 

    
        
    

            
You construct a JSF DataTable that displays the current hotels list, and then place a "More Results" link below the table:
 

            
This commandLink signals a "next" event from its action attribute. You can then handle the event by adding to the view-state definition:
 

    
        
    
    
        
    

            
Here you handle the "next" event by incrementing the page count on the searchCriteria instance. The on-render action is then called again with the updated criteria, which causes the next page of results to be loaded into the DataModel. The same view is re-rendered since there was no toattribute on the transition element, and the changes in the model are reflected in the view.

Handling JSF Action Events

The next logical level beyond in-page events are events that require navigation to another view, with some manipulation of the model along the way. Achieving this with pure JSF would require adding a navigation rule to faces-config.xml and likely some intermediary Java code in a JSF managed bean (both tasks requiring a re-deploy). With the flow defintion language, you can handle such a case concisely in one place in a quite similar way to how in-page events are handled.
Continuing on with our use case of manipulating a paged list of results, suppose we want each row in the displayed DataTable to contain a link to a detail page for that row instance. You can add a column to the table containing the following commandLink component:

            
This raises the "select" event which you can then handle by adding another transition element to the existing view-state :
 

    
        
    
    
        
    
    
            
    

            
Here the "select" event is handled by pushing the currently selected hotel instance from the DataTable into flow scope, so that it may be referenced by the "reviewHotel" view-state .

Performing Model Validation

JSF provides useful facilities for validating input at field-level before changes are applied to the model, but when you need to then perform more complex validation at the model-level after the updates have been applied, you are generally left with having to add more custom code to your JSF action methods in the managed bean. Validation of this sort is something that is generally a responsibility of the domain model itself, but it is difficult to get any error messages propagated back to the view without introducing an undesirable dependency on the JSF API in your domain layer.
With Web Flow, you can utilize the generic and low-level MessageContext in your business code and any messages added there will then be available to the FacesContext at render time.
For example, suppose you have a view where the user enters the necessary details to complete a hotel booking, and you need to ensure the Check In and Check Out dates adhere to a given set of business rules. You can invoke such model-level validation from a transition element:
 

    
        
    

            
Here the "proceed" event is handled by invoking a model-level validation method on the booking instance, passing the generic MessageContext instance so that messages may be recorded. The messages can then be displayed along with any other JSF messages with the h:messagescomponent,

Handling Ajax Events In JSF 2.0

JSF 2 provides built-in support for sending Ajax requests and performing partial processing and rendering on the server-side. You can specify a list of id's for partial rendering through the facelets tag.
In Spring Web Flow you also have the option to specify the ids to use for partial rendering on the server side with the render action:

    
        
    
    
        
        
    

      

Handling File Uploads with JSF

Most JSF component providers include some form of 'file upload' component. Generally when working with these components JSF must take complete control of parsing multi-part requests and Spring MVC's MultipartResolver cannot be used.
Spring Web Flow has been tested with file upload components from PrimeFaces and RichFaces. Check the documentation of your JSF component library for other providers to see how to configure file upload.

File Uploads with PrimeFaces

PrimeFaces provides a  component for uploading files. In order to use the component you need to configure the org.primefaces.webapp.filter.FileUploadFilter servlet filter. The filter needs to be configured against Spring MVC's DispatcherServlet in yourweb.xml:

 PrimeFaces FileUpload Filter
 org.primefaces.webapp.filter.FileUploadFilter


 PrimeFaces FileUpload Filter
 Spring MVC Dispatcher Servlet

   
For more details refer to the PrimeFaces documentation.

File Uploads with RichFaces

RichFaces provides a  component for uploading files. No special configuration is required to use the component, however, you will need to perform some additional steps in your fileUploadListener.
Here is some typical XHTML markup. In this example the fileUploadBean refers to Spring singleton bean.

Within your fileUploadBean you need to tell Web Flow that the response has been handled and that it should not attempt any redirects. The org.springframework.webflow.context.ExternalContext interface provides a recordResponseComplete() for just such purposes.
In addition, it is imperative that some partial response data is returned to the client. If your  component does not specify a render attribute you may need to call processPartial(PhaseId.RENDER_RESPONSE) on the JSF PartialViewContext.
public class FileUploadBean {

 public void listener(FileUploadEvent event) throws Exception{
  FacesContext.getCurrentInstance().getPartialViewContext().processPartial(PhaseId.RENDER_RESPONSE);
  ExternalContextHolder.getExternalContext().recordResponseComplete();
  UploadedFile file = event.getUploadedFile();
  // Do something with the file
 }
}
For more details refer to the RichFaces documentation.

Handling Ajax Events In JSF 1.2

For JSF 1.2 the Spring Faces UICommand components have the ability to do Ajax-based partial view updates. These components degrade gracefully so that the flow will still be fully functional by falling back to full page refreshes if a user with a less capable browser views the page.
Revisiting the earlier example with the paged table, you can change the "More Results" link to use an Ajax request by replacing the standard commandButton with the Spring Faces component version (note that the Spring Faces command components use Ajax by default, but they can alternately be forced to use a normal form submit by setting ajaxEnabled="false" on the component):
            

            
This event is handled just as in the non-Ajax case with the transition element, but now you will add a special render action that specifies which portions of the component tree need to be re-rendered:

    
        
    
    
        
        
    

            
The fragments="hotels:searchResultsFragment" is an instruction that will be interpreted at render time, such that only the component with the JSF clientId "hotels:searchResultsFragment" will be rendered and returned to the client. This fragment will then be automatically replaced in the page. The fragments attribute can be a comma-delimited list of ids, with each id representing the root node of a subtree (meaning the root node and all of its children) to be rendered. If the "next" event is fired in a non-Ajax request (i.e., if JavaScript is disabled on the client), the renderaction will be ignored and the full page will be rendered as normal.
In addition to the Spring Faces commandLink component, there is a corresponding commandButton component with the same functionality. There is also a special ajaxEvent component that will raise a JSF action even in response to any client-side DOM event. See the Spring Faces tag library docs for full details.
An additional built-in feature when using the Spring Faces Ajax-enabled components is the ability to have the response rendered inside a rich modal popup widget by setting popup="true" on a view-state .

    
        
    
    
        
    

            
If the "changeSearchCriteria" view-state is reached as the result of an Ajax-request, the result will be rendered into a rich popup. If JavaScript is unavailable, the request will be processed with a full browser refresh, and the "changeSearchCriteria" view will be rendered as normal.

Embedding a Flow On a Page

By default when a flow enters a view state, it executes a client-side redirect before rendering the view. This approach is known as POST-REDIRECT-GET. It has the advantage of separating the form processing for one view from the rendering of the next view. As a result the browser Back and Refresh buttons work seamlessly without causing any browser warnings.
Normally the client-side redirect is transparent from a user's perspective. However, there are situations where POST-REDIRECT-GET may not bring the same benefits. For example sometimes it may be useful to embed a flow on a page and drive it via Ajax requests refreshing only the area of the page where the flow is rendered. Not only is it unnecessary to use client-side redirects in this case, it is also not the desired behavior with regards to keeping the surrounding content of the page intact.
To indicate a flow should execute in "page embedded" mode all you need to do is pass an extra flow input attribute called "mode" with a value of "embedded". Below is an example of a top-level container flow invoking a sub-flow in an embedded mode:

    

    
When launched in "page embedded" mode the sub-flow will not issue flow execution redirects during Ajax requests.
If you'd like to see examples of an embedded flow please refer to the webflow-primefaces-showcase project. You can check out the source code locally, build it as you would a Maven project, and import it into Eclipse:
cd some-directory
svn co https://src.springframework.org/svn/spring-samples/webflow-primefaces-showcase
cd webflow-primefaces-showcase
mvn package
# import into Eclipse
The specific example you need to look at is under the "Advanced Ajax" tab and is called "Top Flow with Embedded Sub-Flow".

Redirect In Same State

By default Web Flow does a client-side redirect even it it remains in the same view state as long as the current request is not an Ajax request. This is quite useful after form validation failures for example. If the user hits Refresh or Back they won't see any browser warnings. They would if the Web Flow didn't do a redirect.
This can lead to a problem specific to JSF 2 environments where a specific Sun Mojarra listener component caches the FacesContext assuming the same instance is available throughout the JSF lifecycle. In Web Flow however the render phase is temporarily put on hold and a client-side redirect executed.
The default behavior of Web Flow is desirable and it is unlikely JSF 2 applications will experience the issue. This is because Ajax is often enabled the default in JSF 2 component libraries and Web Flow does not redirect during Ajax requests. However if you experience this issue you can disable client-side redirects within the same view as follows:

 
  
 

  

Using the Spring Security Facelets Tag Library

To use the library you'll need to create a .taglib.xml file and register it in web.xml.
For JSF 2 create the file /WEB-INF/springsecurity.taglib.xml with the following content:


 http://www.springframework.org/security/tags
 
  authorize
  org.springframework.faces.security.FaceletsAuthorizeTagHandler
 
 
  areAllGranted
  org.springframework.faces.security.FaceletsAuthorizeTagUtils
  boolean areAllGranted(java.lang.String)
 
 
  areAnyGranted
  org.springframework.faces.security.FaceletsAuthorizeTagUtils
  boolean areAnyGranted(java.lang.String)
 
 
  areNotGranted
  org.springframework.faces.security.FaceletsAuthorizeTagUtils
  boolean areNotGranted(java.lang.String)
 
 
  isAllowed
  org.springframework.faces.security.FaceletsAuthorizeTagUtils
  boolean isAllowed(java.lang.String, java.lang.String)
 

For JSF 1.2 also create the file /WEB-INF/springsecurity.taglib.xml but with the following content instead:


 http://www.springframework.org/security/tags
 
  authorize
  org.springframework.faces.security.Jsf12FaceletsAuthorizeTagHandler
 
 
  areAllGranted
  org.springframework.faces.security.Jsf12FaceletsAuthorizeTagUtils
  boolean areAllGranted(java.lang.String)
 
 
  areAnyGranted
  org.springframework.faces.security.Jsf12FaceletsAuthorizeTagUtils
  boolean areAnyGranted(java.lang.String)
 
 
  areNotGranted
  org.springframework.faces.security.Jsf12FaceletsAuthorizeTagUtils
  boolean areNotGranted(java.lang.String)
 
 
  isAllowed
  org.springframework.faces.security.Jsf12FaceletsAuthorizeTagUtils
  boolean isAllowed(java.lang.String, java.lang.String)
 

Next, register the above file taglib in web.xml:

    javax.faces.FACELETS_LIBRARIES
    /WEB-INF/springsecurity.taglib.xml

Now you are ready to use the tag library in your views. You can use the authorize tag to include nested content conditionally:


 
  Lorem ipsum dolor sit amet
 

 
  Lorem ipsum dolor sit amet
 

 
  Lorem ipsum dolor sit amet
 

    
You can also use one of several EL functions in the rendered or other attribute of any JSF component:


 
  
 
 
  
 
 
  
 
 
  

    

Enhancing The User Experience With Rich Web Forms in JSF 1.2

JSF and Web Flow combine to provide an extensive server-side validation model for your web application, but excessive roundtrips to the server to execute this validation and return error messages can be a tedious experience for your users. The Spring Faces component library provides a number of client-side rich validation controls that can enhance the user experience by applying simple validations that give immediate feedback. Some simple examples are illustrated below. See the Spring Faces taglib docs for a complete tag reference.

Validating a Text Field

Simple client-side text validation can be applied with the clientTextValidator component:
 

    

            
This will apply client-side required validation to the child inputText component, giving the user a clear indicator if the field is left blank.

Validating a Numeric Field

Simple client-side numeric validation can be applied with the clientNumberValidator component:
 

    

            
This will apply client-side validation to the child inputText component, giving the user a clear indicator if the field is left blank, is not numeric, or does not match the given regular expression.

Validating a Date Field

Simple client-side date validation with a rich calendar popup can be applied with the clientDateValidator component:
 

    
        
    

            
This will apply client-side validation to the child inputText component, giving the user a clear indicator if the field is left blank or is not a valid date.

Preventing an Invalid Form Submission

The validateAllOnClick component can be used to intercept the "onclick" event of a child component and suppress the event if all client-side validations do not pass.
 

     

            
This will prevent the form from being submitted when the user clicks the "proceed" button if the form is invalid. When the validations are executed, the user is given clear and immediate indicators of the problems that need to be corrected.

Third-Party Component Library Integration

The Spring Web Flow JSF integration strives to be compatible with any third-party JSF component library. By honoring all of the standard semantics of the JSF specification within the SWF-driven JSF lifecycle, third-party libraries in general should "just work". The main thing to remember is that configuration in web.xml will change slightly since Web Flow requests are not routed through the standard FacesServlet. Typically, anything that is traditionally mapped to the FacesServlet should be mapped to the Spring DispatcherServlet instead. (You can also map to both if for example you are migrating a legacy JSF application page-by-page.) In some cases, a deeper level of integration can be achieved by configuring special flow services that are "aware" of a particular component library, and these will be noted in the examples to follow.

Rich Faces Integration (JSF 1.2)

To use the Rich Faces component library with Spring Web Flow, the following filter configuration is needed in web.xml (in addition to the other typical configuration already shown):
 
 
    RichFaces Filter 
    richfaces 
    org.ajax4jsf.Filter 
 

 
    richfaces 
    Spring Web MVC Dispatcher Servlet
    REQUEST
    FORWARD
    INCLUDE

            
For deeper integration (including the ability to have a view with combined use of the Spring Faces Ajax components and Rich Faces Ajax components), configure the RichFacesAjaxHandler on your FlowController:
 

    
    
        
    

            
RichFaces Ajax components can be used in conjunction with the render tag to render partial fragments on an Ajax request. Instead of embedding the ids of the components to be re-rendered directly in the view template (as you traditionally do with Rich Faces), you can bind the reRenderattribute of a RichFaces Ajax component to a special flowRenderFragments EL variable. For example, in your view template you can have a fragment that you would potentially like to re-render in response to a particular event:

    
        
        
            
                Name
                #{hotel.name}
            
            
                Address
                #{hotel.address}
            
        
    

            
then a RichFaces Ajax commandLink to fire the event:

            
and then in your flow definition a transition to handle the event:

    
    

            

Apache MyFaces Trinidad Integration (JSF 1.2)

The Apache MyFaces Trinidad library has been tested with the Spring Web Flow's JSF integration and proven to fit in nicely. Deeper integration to allow the Trinidad components and Spring Faces components to play well together has not yet been attempted, but Trinidad provides a pretty thorough solution on its own when used in conjunction with the Spring Web Flow JSF integration.
NOTE: An AjaxHandler implementation for Trinidad is not currently provided out-of-the-box. In order to fully integrate with Trinidad's PPR functionality, a custom implementation should be provided. An community-provided partial example can be found here: SWF-1160
Typical configuration when using Trinidad with Web Flow is as follows in web.xml (in addition what has already been shown):

    javax.faces.STATE_SAVING_METHOD
    server



    
        org.apache.myfaces.trinidad.CHANGE_PERSISTENCE
    
    session



    
        org.apache.myfaces.trinidad.ENABLE_QUIRKS_MODE
    
    false



    Trinidad Filter
    
        org.apache.myfaces.trinidad.webapp.TrinidadFilter
    



    Trinidad Filter
    Spring MVC Dispatcher Servlet



    Trinidad Resource Servlet
    
        org.apache.myfaces.trinidad.webapp.ResourceServlet
    



    resources
    /adf/*


            

Chapter 14. Portlet Integration

Introduction

This chapter shows how to use Web Flow in a Portlet environment. Spring Web Flow requires Portlet API 2.0 to run with. The booking-portlet-mvc sample application is a good reference for using Web Flow within a portlet. This application is a simplified travel site that allows users to search for and book hotel rooms.

Configuring web.xml and portlet.xml

The configuration for a portlet depends on the portlet container used. The sample applications, included with Web Flow, are both configured to use Apache Pluto.
In general, the configuration requires adding a servlet mapping in the web.xml file to dispatch request to the portlet container.

    swf-booking-mvc
    org.apache.pluto.core.PortletServlet
    
        portlet-name
        swf-booking-mvc
    
    1



    swf-booking-mvc
    /PlutoInvoker/swf-booking-mvc

  
The portlet.xml configuration is a standard portlet configuration. The portlet-class needs to be set along with a pair of init-params. Setting the expiration-cache to 0 is recommended to force Web Flow to always render a fresh view.

    ...
    org.springframework.web.portlet.DispatcherPortlet
    
        contextConfigLocation
        /WEB-INF/web-application-config.xml
    
    
        viewRendererUrl
        /WEB-INF/servlet/view
    
    0
    ...

  

Configuring Spring

Flow Handlers

The only supported mechanism for bridging a portlet request to Web Flow is a FlowHandler. The PortletFlowController used in Web Flow 1.0 is no longer supported.
The flow handler, similar to the servlet flow handler, provides hooks that can:
  • select the flow to execute
  • pass input parameters to the flow on initialization
  • handle the flow execution outcome
  • handle exceptions

The AbstractFlowHandler class is an implementation of FlowHandler that provides default implementations for these hooks.
In a portlet environment the targeted flow id can not be inferred from the URL and must be defined explicitly in the handler.
public class ViewFlowHandler extends AbstractFlowHandler {
    public String getFlowId() {
        return "view";
    }
}
   

Handler Mappings

Spring Portlet MVC provides a rich set of methods to map portlet requests. Complete documentation is available in the Spring Reference Documentation.
The booking-portlet-mvc sample application uses a PortletModeHandlerMapping to map portlet requests. The sample application only supports view mode, but support for other portlet modes is available. Other modes can be added and point to the same flow as view mode, or any other flow.

    
        
            
                
            
        
    

   

Flow Handler Adapter

FlowHandlerAdapter converts the handler mappings to the flow handlers. The flow executor is required as a constructor argument.

    

   

Portlet Views

In order to facilitate view rendering, a ViewRendererServlet must be added to the web.xml file. This servlet is not invoked directly, but it used by Web Flow to render views in a portlet environment.

    ViewRendererServlet
    org.springframework.web.servlet.ViewRendererServlet



    ViewRendererServlet
    /WEB-INF/servlet/view

  

Portlet Modes and Window States

Window State

The Portlet API defined three window states: normal, minimized and maximized. The portlet implementation must decide what to render for each of these window states. Web Flow exposes the string value of the window state under portletWindowState via the request map on the external context.
requestContext.getExternalContext().getRequestMap().get("portletWindowState");
   
externalContext.requestMap.portletWindowState
   

Portlet Mode

The Portlet API defined three portlet modes: view, edit and help. The portlet implementation must decide what to render for each of these modes. Web Flow exposes the string value of the portlet mode under portletMode via the request map on the external context.
requestContext.getExternalContext().getRequestMap().get("portletMode");
   
externalContext.requestMap.portletMode
   

Using Portlets with JSF

Prior to version 2.1 of Spring Web Flow, support for JSF Portlets was considered experimental and relied on a Portlet Bridge for JSF implementation. Furthermore JSR-329 (the latest specification in this area), which targets Portlet API 2.0 and JSF 1.2 environments at the time of writing is not yet final causing portlet bridge implementations to also remain incomplete.
A closer comparison of Spring Web Flow and a Portlet Bridge for JSF shows the two have significant overlap. They both drive the JSF lifecycle and they both shield JSF from knowledge about Portlet action and render requests.
Considering all of the above, starting with version 2.2, Spring Web Flow provides support for JSF Portlets using its own internal Portlet integration rather than a Portlet Bridge for JSF. We believe this will provide value for Web Flow users by reducing the number of dependencies in what is already a fairly complex combination of technologies with specifications lagging behind.
What this practically means is the configuration required for JSF Portlets is very similar to what is alread documented in the rest of this chapter with the exception of the section called “Portlet Views”, which is not necessary with JSF.
Review the swf-booking-portlet-faces sample in the Web Flow distribution for a working JSF Portlets example with complete configuration details. The main thing you'll need to notice in addition to what has already been described in this chapter is the faces-config.xmlconfiguration:



    
        
            org.springframework.faces.webflow.application.portlet.PortletFaceletViewHandler
          
    

Issues in a Portlet Environment

Redirects

The Portlet API only allows redirects to be requested from an action request. Because views are rendered on the render request, views and view-states cannot trigger a redirect.
The externalRedirect: view prefix is a convenience for Servlet based flows. An IllegalStateException is thrown if a redirect is requested from a render request.
end-state redirects can be achieved by implementing FlowHandler.handleExecutionOutcome. This callback provides the ActionResponse object which supports redirects.

Switching Portlet Modes

The portlet container passes the execution key from the previous flow when switching to a new mode. Even if the mode is mapped to a different FlowHandler the flow execution will resume the previous execution. You may switch the mode programatically in your FlowHandler after ending a flow in an ActionRequest.
One way to start a new flow is to create a URL targeting the mode without the execution key.

Chapter 15. Testing flows

Introduction

This chapter shows you how to test flows.

Extending AbstractXmlFlowExecutionTests

To test the execution of a XML-based flow definition, extend AbstractXmlFlowExecutionTests:
public class BookingFlowExecutionTests extends AbstractXmlFlowExecutionTests {

}
  

Specifying the path to the flow to test

At a minimum, you must override getResource(FlowDefinitionResourceFactory) to return the path to the flow you wish to test:
@Override
protected FlowDefinitionResource getResource(FlowDefinitionResourceFactory resourceFactory) {
    return resourceFactory.createFileResource("src/main/webapp/WEB-INF/hotels/booking/booking.xml");
}
  

Registering flow dependencies

If your flow has dependencies on externally managed services, also override configureFlowBuilderContext(MockFlowBuilderContext) to register stubs or mocks of those services:
@Override
protected void configureFlowBuilderContext(MockFlowBuilderContext builderContext) {
    builderContext.registerBean("bookingService", new StubBookingService());
}
        
If your flow extends from another flow, or has states that extend other states, also override getModelResources(FlowDefinitionResourceFactory) to return the path to the parent flows.
@Override
protected FlowDefinitionResource[] getModelResources(FlowDefinitionResourceFactory resourceFactory) {
   return new FlowDefinitionResource[] {
       resourceFactory.createFileResource("src/main/webapp/WEB-INF/common/common.xml")
   };
}
  

Testing flow startup

Have your first test exercise the startup of your flow:
public void testStartBookingFlow() {

    Booking booking = createTestBooking();

    MutableAttributeMap input = new LocalAttributeMap();
    input.put("hotelId", "1");
    MockExternalContext context = new MockExternalContext();
    context.setCurrentUser("keith");
    startFlow(input, context);

    assertCurrentStateEquals("enterBookingDetails");
    assertTrue(getRequiredFlowAttribute("booking") instanceof Booking);
}
        
Assertions generally verify the flow is in the correct state you expect.

Testing flow event handling

Define additional tests to exercise flow event handling behavior. You goal should be to exercise all paths through the flow. You can use the convenient setCurrentState(String) method to jump to the flow state where you wish to begin your test.
public void testEnterBookingDetails_Proceed() {

    setCurrentState("enterBookingDetails");
    
    getFlowScope().put("booking", createTestBooking());

    MockExternalContext context = new MockExternalContext();
    context.setEventId("proceed");
    resumeFlow(context);

    assertCurrentStateEquals("reviewBooking");
}
  

Mocking a subflow

To test calling a subflow, register a mock implementation of the subflow that asserts input was passed in correctly and returns the correct outcome for your test scenario.
public void testBookHotel() {
    
    setCurrentState("reviewHotel");

    Hotel hotel = new Hotel();
    hotel.setId(1L);
    hotel.setName("Jameson Inn");
    getFlowScope().put("hotel", hotel);

    getFlowDefinitionRegistry().registerFlowDefinition(createMockBookingSubflow());

    MockExternalContext context = new MockExternalContext();
    context.setEventId("book");
    resumeFlow(context);

    // verify flow ends on 'bookingConfirmed'
    assertFlowExecutionEnded();
    assertFlowExecutionOutcomeEquals("finish");
}

public Flow createMockBookingSubflow() {
    Flow mockBookingFlow = new Flow("booking");
    mockBookingFlow.setInputMapper(new Mapper() {
        public MappingResults map(Object source, Object target) {
            // assert that 1L was passed in as input
            assertEquals(1L, ((AttributeMap) source).get("hotelId"));
            return null;
        }
    });
    // immediately return the bookingConfirmed outcome so the caller can respond
    new EndState(mockBookingFlow, "bookingConfirmed");
    return mockBookingFlow;
}
  

Chapter 16. Upgrading from 1.0

Introduction

This chapter shows you how to upgrade existing Web Flow 1 application to Web Flow 2.

Flow Definition Language

The core concepts behind the flow definition language have not changed between Web Flow 1 and 2. However, some of the element and attribute names have changed. These changes allow for the language to be both more concise and expressive. A complete list of mapping changes is available as an appendix.

Flow Definition Updater Tool

An automated tool is available to aid in the conversion of existing 1.x flows to the new 2.x style. The tool will convert all the old tag names to their new equivalents, if needed. While the tool will make a best effort attempt at conversion, there is not a one-to-one mapping for all version 1 concepts. If the tool was unable to convert a portion of the flow, it will be marked with a WARNING comment in the resulting flow.
The conversion tool requires spring-webflow.jar, spring-core.jar and an XSLT 1.0 engine. Saxon 6.5.5 is recommended.
The tool can be run from the command line with the following command. Required libraries must be available on the classpath. The source must be a single flow to convert. The resulting converted flow will be sent to standard output.
java org.springframework.webflow.upgrade.WebFlowUpgrader flow-to-upgrade.xml
   

Flow Definition Updater Tool Warnings

argument parameter-type no longer supported
Bean actions have been deprecated in favor of EL based evaluate expressions. The EL expression is able to accept method parameters directly, so there is no longer a need for the argument tag. A side effect of this change is that method arguments must be of the correct type before invoking the action.
inline-flow is no longer supported
Inline flows are no longer supported. The contents of the inline flow must be moved into a new top-level flow. The inline flow's content has been converted for your convenience.
mapping target-collection is no longer supported
Output mappings can no longer add an item to a collection. Only assignment is supported.
var bean is no longer supported
The var bean attribute is no longer needed. All spring beans can be resolved via EL.
var scope is no longer supported
The var element will place all variable into flow scope. Conversation scope was previously allowed.

EL Expressions

EL expressions are used heavily throughout the flow definition language. Many of the attributes that appear to be plain text are actually interpreted as EL. The standard EL delimiters (either ${} or #{} in Web Flow 2.0 or just #{} in Web Flow 2.1) are not necessary and will often cause an exception if they are included.
EL delimiters should be removed where necessary by the updater tool.

Web Flow Configuration

In Web Flow 1 there were two options available for configuring Web Flow, one using standard spring bean XML and the other using the webflow-config-1.0 schema. The schema configuration option simplifies the configuration process by keeping long internal class names hidden and enabling contextual auto-complete. The schema configuration option is the only way to configure Web Flow 2.

Web Flow Bean Configuration

The FactoryBean bean XML configuration method used in Web Flow 1 is no longer supported. The schema configuration method should be used instead. In particular beans defining FlowExecutorFactoryBean and XmlFlowRegistryFactoryBean should be updated. Continue reading Web Flow Schema Configuration for details.

Web Flow Schema Configuration

The webflow-config configuration schema has also changed slightly from version 1 to 2. The simplest way to update your application is modify the version of the schema to 2.0 then fix any errors in a schema aware XML editor. The most common change is add 'flow-' to the beginning of the elements defined by the schema.

   

flow-executor

The flow executor is the core Web Flow configuration element. This element replaces previous FlowExecutorFactoryBean bean definitions.

    

flow-execution-listeners

Flow execution listeners are also defined in the flow executor. Listeners are defined using standard bean definitions and added by reference.

    
        
    



    

flow-registry

The flow-registry contains a set of flow-locations. Every flow definition used by Web Flow must be added to the registry. This element replaces previous XmlFlowRegistryFactoryBean bean definitions.

    

    

Flow Controller

The package name for flow controllers has changed from org.springframework.webflow.executor.mvc.FlowController and is now org.springframework.webflow.mvc.servlet.FlowController for Servlet MVC requests. The portlet flow controllerorg.springframework.webflow.executor.mvc.PortletFlowController has been replaced by a flow handler adapter available at org.springframework.webflow.mvc.portlet.FlowHandlerAdapter. They will need to be updated in the bean definitions.

Flow URL Handler

The default URL handler has changed in Web Flow 2. The flow identifier is now derived from the URL rather then passed explicitly. In order to maintain comparability with existing views and URL structures a WebFlow1FlowUrlHandler is available.

    
    
        
    

   

View Resolution

Web Flow 2 by default will both select and render views. View were previously selected by Web Flow 1 and then rendered by an external view resolver.
In order for version 1 flows to work in Web Flow 2 the default view resolver must be overridden. A common use case is to use Apache Tiles for view resolution. The following configuration will replace the default view resolver with a Tiles view resolver. The tilesViewResolver in this example can be replaced with any other view resolver.

 
    ...





    



    



    

   

New Web Flow Concepts

Automatic Model Binding

Web Flow 1 required Spring MVC based flows to manually call FormAction methods, notably: setupFormbindAndValidate to process form views. Web Flow 2 now provides automatic model setup and binding using the model attribute for view-states. Please see the Binding to a Model section for details.

OGNL vs Spring EL

Web Flow 1 used OGNL exclusively for expressions within the flow definitions. Web Flow 2 adds support for Unified EL. Web Flow 2.1 uses Spring EL by default. United EL and OGNL can still be plugged in. Please see Chapter 4, Expression Language (EL) for details.

Flash Scope

Flash scope in Web Flow 1 lived across the current request and into the next request. This was conceptually similar to Web Flow 2's view scope concept, but the semantics were not as well defined. In Web Flow 2, flash scope is cleared after every view render. This makes flashScope semantics in Web Flow consistent with other web frameworks.

JSF

Web Flow 2 offers significantly improved integration with JSF. Please see Chapter 13, JSF Integration for details.

External Redirects

External redirects in Web Flow 1 were always considered context relative. In Web Flow 2, if the redirect URL begins with a slash, it is considered servlet-relative instead of context-relative. URLs without a leading slash are still context relative.

Appendix A. Flow Definition Language 1.0 to 2.0 Mappings

The flow definition language has changed since the 1.0 release. This is a listing of the language elements in the 1.0 release, and how they map to elements in the 2.0 release. While most of the changes are semantic, there are a few structural changes. Please see the upgrade guide for more details about changes between Web Flow 1.0 and 2.0.
Table A.1. Mappings
SWF 1.0SWF 2.0Comments
action*use
 bean * 
 name * 
 method * 
action-stateaction-state 
 id id 
 * parent 
argument*use
 expression   
 parameter-type   
attributeattribute 
 name name 
 type type 
 value value 
attribute-mapper*input and output elements can be in flows or subflows directly
 bean *now subflow-attribute-mapper attribute on subflow-state
bean-action*use
 bean * 
 name * 
 method * 
decision-statedecision-state 
 id id 
 * parent 
end-actionson-end 
end-stateend-state 
 id id 
 view view 
 * parent 
 * commit 
entry-actionson-entry 
evaluate-actionevaluate 
 expression expression 
 name *use
 * result 
 * result-type 
evaluation-result*use
 name * 
 scope * 
exception-handlerexception-handler 
 bean bean 
exit-actionson-exit 
flowflow 
 * start-state 
 * parent 
 * abstract 
global-transitionsglobal-transitions 
ifif 
 test test 
 then then 
 else else 
importbean-import 
 resource resource 
inline-flow*convert to new top-level flow
 id * 
input-attributeinput 
 name name 
 scope *prefix name with scope
 required required 
 * type 
 * value 
input-mapper*inputs can be in flows and subflows directly
mappinginput or output 
 source name or valuename when in flow element, value when in subflow-state element
 target name or valuevalue when in flow element, name when in subflow-state element
 target-collection *no longer supported
 from *detected automatically
 to type 
 required required 
method-argument*use
method-result*use
 name * 
 scope * 
output-attributeoutput 
 name name 
 scope *prefix name with scope
 required required 
 * type 
 * value 
output-mapper*output can be in flows and subflows directly
render-actionson-render 
setset 
 attribute name 
 scope *prefix name with scope
 value value 
 name *use
 * type 
start-actionson-start 
start-state*now , or defaults to the first state in the flow
 idref * 
subflow-statesubflow-state 
 id id 
 flow subflow 
 * parent 
 * subflow-attribute-mapper 
transitiontransition 
 on on 
 on-exception on-exception 
 to to 
 * bind 
 * validate 
 * history 
valuevalue 
varvar 
 name name 
 class class 
 scope *always flow scope
 bean *all Spring beans can be resolved with EL
view-stateview-state 
 id id 
 view view 
 * parent 
 * redirect 
 * popup 
 * model 
 * history 
*persistence-context 
*render 
 * fragments 
*secured 
 * attributes 
 * match