JBoss, Geronimo, or Tomcat?

Java EE feature comparison

Feature	JBoss 4.2	Geronimo 2	Tomcat 6
Java EE 5 compliance	Partial	Yes	No
EJB 3.0 capable	Yes	Yes	Available
JSP 2.1 and Servlet 2.5 capable	Yes	Yes	Yes
JavaServer Faces 1.2 support	Yes	Yes	Available
Custom plug-in support	Yes	Yes	No
Business-rules engine support	Available	Available	Available
Hibernate 3.x support	Yes	Available	Available
JBoss Seam support	Yes	Yes	Available
Clustering support	Yes	Yes	Partial
Eclipse IDE connector support	Yes	Yes	Yes

Geronimo 2 is the clear choice if your Java application needs are particularly extensive or if you just want to leverage total Java EE 5 compliance. Although JBoss 4.2 is not completely compatible with Sun's Java EE 5 standard, the JBoss 4.2 team is responsible for many of the cutting-edge technologies used by all of the servers and added to the standard Java EE 5 capabilities. Tomcat 6 by itself is a lightweight solution. It does not come with all the JEE features and additional packages found in JBoss and Geronimo, but also doesn't require much memory and runs fast even on smaller servers.

Now, let's look at why these features matter.