STR:

1) Install JON 2.3.0 and JBoss AS/EAP plugins
2) Install EAP 4.2.0 and let an agent monitor it
3) tail -f rhq_agent/logs/rhq_agent.log
4) Wait for this exception:

...
2010-06-14 23:00:38,484 INFO  [InventoryManager.discovery-1] (rhq.core.pc.inventory.AutoDiscoveryExecutor)- Executing server discovery scan...
2010-06-14 23:00:47,699 INFO  [ResourceDiscoveryComponent.invoker.daemon-2597] (org.rhq.plugins.agent.AgentDiscoveryComponent)- Discovering RHQ Agent...
2010-06-14 23:00:47,719 ERROR [InventoryManager.discovery-1] (rhq.core.pc.inventory.AutoDiscoveryExecutor)- Error in auto discovery
java.lang.NoClassDefFoundError: org/rhq/core/pluginapi/inventory/ManualAddFacet
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:616)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:260)
        at java.net.URLClassLoader.access$000(URLClassLoader.java:56)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:195)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:303)
        at org.rhq.core.pc.plugin.PluginClassLoader.loadClass(PluginClassLoader.java:63)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:316)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:247)
        at org.rhq.core.pc.plugin.PluginComponentFactory.instantiateClass(PluginComponentFactory.java:228)
        at org.rhq.core.pc.plugin.PluginComponentFactory.getDiscoveryComponent(PluginComponentFactory.java:110)
        at org.rhq.core.pc.inventory.AutoDiscoveryExecutor.pluginDiscovery(AutoDiscoveryExecutor.java:170)
        at org.rhq.core.pc.inventory.AutoDiscoveryExecutor.call(AutoDiscoveryExecutor.java:104)
        at org.rhq.core.pc.inventory.AutoDiscoveryExecutor.run(AutoDiscoveryExecutor.java:92)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
        at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
        at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:181)
        at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:205)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.ClassNotFoundException: org.rhq.core.pluginapi.inventory.ManualAddFacet
        at java.net.URLClassLoader$1.run(URLClassLoader.java:200)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:188)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:303)
        at org.rhq.core.pc.plugin.PluginClassLoader.loadClass(PluginClassLoader.java:63)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:316)
        ... 28 more
2010-06-14 23:00:47,722 INFO  [InventoryManager.discovery-1] (rhq.core.pc.inventory.AutoDiscoveryExecutor)- Process scan auto-detected new server resource: scan=[ProcessScan: query=[process|basename|match=^java.*,arg|org.jboss.Main|match=.*], name=[JBoss4]], discovered-process=[process: pid=[20301], name=[/mnt/jqa/jdk1.6.0_17-x86_64/bin/java], ppid=[20275]]
...