This FAQ addresses the main questions about the changes that have occured between JBossAS 4.x and 5.0.x likely to affect users.

Q1: How do I find out where a class was loaded from?

A1: The unified loader repository mbeans have been replaced by new class loader mbeans.

1) http://localhost:8080/jmx-console

2) Click on
jboss.classloader:type=ClassLoader,id=DeploymentDoingTheLoadClass

(alternatively if you don't know which classloader is being used,
find your (sub)deployment/component in the jboss.deployment
list and click "view mbean" on its ClassLoaderName attribute)

3) From the classloader mbean run the managed operation

findClassLoaderForClass(ClassName)

Q2: How do I migrate my EJB 3 beans?

Answer: See the EJB 3 migration guide From AS 5.0.0.Beta3 to 5.0.0.CR2.

Q3: Where are the .deployer configurations?

Answer: They have been moved to a seperate server/xxx/deployers folder, they used to be in server/xxx/deploy

Q4: How do I enable isolated classloading for ears?

Answer: The default isolated flag has been moved to a new EARClassLoaderDeployer in server/xxx/deployers/ear-deployer-jboss-beans.xml. The related call-by-value default value is on the JBossAppParsingDeployer in the same file.

Q5: How can I load war resources like WEB-INF/some.xml using the classloader?

Answer: In JBoss5 we have corrected the war classloading such that the root of the war is not in the classpath. The correct place to add resource files visible to the war classloader is WEB-INF/classes. You can however load such resources using the ServletContext.getResource().