Michael Yuan

Darryl Smith pointed out that we can actually use non-JTA transactions with JPA in Tomcat now. So, I just added tomcat 5.5 and 6.0 build targets for the jpa example in CVS based on his suggestions.

In JBoss Seam 2.0, we made some changes to the way Tomcat is supported as a Seam runtime. It has caused some confusion. So, let me try to clarify here …

As you recall, in Seam 1.0 to 1.2, we can run Seam applications on Tomcat by bundling the JBoss Embeddable EJB3 library or the JBoss micro-container inside the WAR application. The application will need to bootstrap the EJB3 container or micro-container upon startup. However, the EJB3 library Jars is more than 20 MB. The idea of bootstraping the entire thing for each application is not very efficient. In Seam 2, we leverage the “Embeddable JBoss” library to provide shared EJB3 service to all WAR applications deployed in the Tomcat instance. You have two ways to run Seam 2 applications in Tomcat:

1. If you need to use EJB3 beans, you will need to install the “Embeddable JBoss” libraries as shared library in Tomcat. It is an easy process. You can find instructions for Tomcat 5.5 and 6.0 respectively. Once you do that, you can deploy Seam applications without any restrictions. You will be able to use full EJB3 features including session beans, entity beans, message driven beans, and web services etc.

Of course, you still cannot deploy EAR files on Tomcat. But you can bundle EJB3 JARs in the WEB-INF/lib directory of your WAR application — essentially re-creating the EAR structure in a WAR. Just run the tomcat.war ANT target on any of the official Seam examples to see how this is done.

2. If you absolutely cannot install any shared library or shared configuration on Tomcat, you can still run Seam applications. However, you will not be able to use EJB3 features — you must use Seam POJOs instead. You can, however, use JPA in local transaction mode. Seam manages the transaction manager and entity manager for you in this case.

Checkout the jpa and hibernate2 examples in Seam distribution and build for the tomcat55 or tomcat6 targets to see how this works. The jpa shows how to use JPA EntityManager with Seam POJOs and the hibernate2 example shows how to use Hibernate sessions with Seam POJOs. You will need to copy hsqldb.jar into Tomcat’s shared lib directory since the example app assumed that we will use a HSQL DB from JNDI (see META-INF/context.xml). Obviously, you do not have to do that in your own apps.

Okay, so much for Tomcat support. What about Seam 2 support for J2EE 1.4 application servers and non-JBoss Java EE 5 application servers? Here are the status:

• J2EE 1.4 application servers: Try the jpa example in Seam distribution. It uses Seam POJOs to replace EJB3 session beans in other examples. The jpa example builds for JBoss 4.0.5/4.2.x, WebSphere 6.1.0.9, and WebLogic 9.2.
• Java EE 5 application servers: Try the jee5 example in Seam distribution. It builds for JBoss AS 5.x, Glassfish V1/V2, and Oracle OC4J 11. We are currently working on WebLogic 10, which has some weird reflection issues.

Hope that helps!