Several issues with deploying a simple JSR 168 Portlet, I will outline the steps first.

1) Create a Dynamic Web Project

2) to the Facets, I have added just "JBoss Core Portlet"

3) To the Build Path, I added portlet-api-2.0.jar from deploy/gatein.ear/lib

4) Create a Portlet (com.jboss.test.Portlet)

5) Add a server with the launch config param.

6) Started the Server, it starts fine.

7) add the Dynamic Web Project to the Server, and it blows up with a cast from com.jboss.test.Portlet cannot be cast to javax.portlet.Portlet

Here is the stack trace:

14:54:49,125 INFO [TomcatDeployment] deploy, ctxPath=/TestPortal
14:54:49,218 ERROR [LifeCycle] Cannot start object
org.gatein.pc.portlet.container.PortletInitializationException: The portlet Portlet threw a runtime exception during init
at org.gatein.pc.portlet.impl.jsr168.PortletContainerImpl.start(PortletContainerImpl.java:289)
at org.gatein.pc.portlet.impl.container.PortletContainerLifeCycle.invokeStart(PortletContainerLifeCycle.java:76)
at org.gatein.pc.portlet.impl.container.LifeCycle.managedStart(LifeCycle.java:93)
at org.gatein.pc.portlet.impl.container.PortletApplicationLifeCycle.startDependents(PortletApplicationLifeCycle.java:351)
at org.gatein.pc.portlet.impl.container.LifeCycle.managedStart(LifeCycle.java:129)
at org.gatein.pc.mc.PortletApplicationDeployment.install(PortletApplicationDeployment.java:153)
at org.gatein.pc.mc.PortletApplicationDeployer.add(PortletApplicationDeployer.java:216)
at org.gatein.pc.mc.PortletApplicationDeployer.onEvent(PortletApplicationDeployer.java:185)
at org.gatein.wci.impl.DefaultServletContainer.safeFireEvent(DefaultServletContainer.java:147)
at org.gatein.wci.impl.DefaultServletContainer.fireEvent(DefaultServletContainer.java:166)
at org.gatein.wci.impl.DefaultServletContainer.access$400(DefaultServletContainer.java:54)
at org.gatein.wci.impl.DefaultServletContainer$RegistrationImpl.registerWebApp(DefaultServletContainer.java:250)
at org.gatein.wci.tomcat.TC6ServletContainerContext.start(TC6ServletContainerContext.java:283)
at org.gatein.wci.tomcat.TC6ServletContainerContext.lifecycleEvent(TC6ServletContainerContext.java:141)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4388)
at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeployInternal(TomcatDeployment.java:310)
at org.jboss.web.tomcat.service.deployers.TomcatDeployment.performDeploy(TomcatDeployment.java:142)
at org.jboss.web.deployers.AbstractWarDeployment.start(AbstractWarDeployment.java:461)
at org.jboss.web.deployers.WebModule.startModule(WebModule.java:118)
at org.jboss.web.deployers.WebModule.start(WebModule.java:97)
at sun.reflect.GeneratedMethodAccessor355.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:616)
at org.jboss.mx.interceptor.ReflectedDispatcher.invoke(ReflectedDispatcher.java:157)
at org.jboss.mx.server.Invocation.dispatch(Invocation.java:96)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:668)
at org.jboss.system.microcontainer.ServiceProxy.invoke(ServiceProxy.java:206)
at $Proxy38.start(Unknown Source)
at org.jboss.system.microcontainer.StartStopLifecycleAction.installAction(StartStopLifecycleAction.java:42)
at org.jboss.system.microcontainer.StartStopLifecycleAction.installAction(StartStopLifecycleAction.java:37)
at org.jboss.dependency.plugins.action.SimpleControllerContextAction.simpleInstallAction(SimpleControllerContextAction.java:62)
at org.jboss.dependency.plugins.action.AccessControllerContextAction.install(AccessControllerContextAction.java:71)
at org.jboss.dependency.plugins.AbstractControllerContextActions.install(AbstractControllerContextActions.java:51)
at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
at org.jboss.system.microcontainer.ServiceControllerContext.install(ServiceControllerContext.java:297)
at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1633)
at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:935)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1083)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:985)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:823)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
at org.jboss.system.ServiceController.doChange(ServiceController.java:688)
at org.jboss.system.ServiceController.start(ServiceController.java:460)
at org.jboss.system.deployers.ServiceDeployer.start(ServiceDeployer.java:163)
at org.jboss.system.deployers.ServiceDeployer.deploy(ServiceDeployer.java:99)
at org.jboss.system.deployers.ServiceDeployer.deploy(ServiceDeployer.java:46)
at org.jboss.deployers.spi.deployer.helpers.AbstractSimpleRealDeployer.internalDeploy(AbstractSimpleRealDeployer.java:62)
at org.jboss.deployers.spi.deployer.helpers.AbstractRealDeployer.deploy(AbstractRealDeployer.java:50)
at org.jboss.deployers.plugins.deployers.DeployerWrapper.deploy(DeployerWrapper.java:171)
at org.jboss.deployers.plugins.deployers.DeployersImpl.doDeploy(DeployersImpl.java:1440)
at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:1158)
at org.jboss.deployers.plugins.deployers.DeployersImpl.doInstallParentFirst(DeployersImpl.java:1179)
at org.jboss.deployers.plugins.deployers.DeployersImpl.install(DeployersImpl.java:1099)
at org.jboss.dependency.plugins.AbstractControllerContext.install(AbstractControllerContext.java:348)
at org.jboss.dependency.plugins.AbstractController.install(AbstractController.java:1633)
at org.jboss.dependency.plugins.AbstractController.incrementState(AbstractController.java:935)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:1083)
at org.jboss.dependency.plugins.AbstractController.resolveContexts(AbstractController.java:985)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:823)
at org.jboss.dependency.plugins.AbstractController.change(AbstractController.java:553)
at org.jboss.deployers.plugins.deployers.DeployersImpl.process(DeployersImpl.java:782)
at org.jboss.deployers.plugins.main.MainDeployerImpl.process(MainDeployerImpl.java:702)
at org.jboss.system.server.profileservice.repository.MainDeployerAdapter.process(MainDeployerAdapter.java:117)
at org.jboss.system.server.profileservice.hotdeploy.HDScanner.scan(HDScanner.java:371)
at org.jboss.system.server.profileservice.hotdeploy.HDScanner.run(HDScanner.java:256)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:351)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:178)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:165)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:267)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:636)
Caused by: java.lang.ClassCastException: com.jboss.test.Portlet cannot be cast to javax.portlet.Portlet
at org.gatein.pc.portlet.impl.jsr168.PortletContainerImpl.start(PortletContainerImpl.java:255)
... 75 more

Now this issue can be worked around by refactoring the Java Class and changing the Portlet.xml. However the refactor of the Java Class does not cause refactor of the portlet.xml