Virgo Tomcat Server OSGi HelloWorld

最近在学osgi，仿照xiaxiayoyo520 http://blog.csdn.net/xiaxiayoyo520/article/details/7490447朋友搭建了一个HelloWorld 的程序，
但是提示一下错误，有谁能解答一下吗？谢谢，最好有一个能运行的实例
[2012-07-11 14:36:31.234] start-signalling-2           <WE0005E> Failed to start web bundle 'GreetUI' version '1.0.0': consult serviceability/logs/log.log for further details. 
[2012-07-11 14:36:31.234] start-signalling-2           <DE0006E> Start failed for bundle 'GreetUI' version '1.0.0'. org.eclipse.virgo.kernel.deployer.core.DeploymentException: Web application failed to start
at org.eclipse.virgo.web.core.internal.WebBundleLifecycleListener.onStarted(WebBundleLifecycleListener.java:132)
at org.eclipse.virgo.kernel.install.artifact.internal.StandardArtifactStateMonitor.onStarted(StandardArtifactStateMonitor.java:247)
at org.eclipse.virgo.kernel.install.artifact.internal.AbstractInstallArtifact.asyncStartSucceeded(AbstractInstallArtifact.java:294)
at org.eclipse.virgo.kernel.install.artifact.internal.AbstractInstallArtifact.access$0(AbstractInstallArtifact.java:291)
at org.eclipse.virgo.kernel.install.artifact.internal.AbstractInstallArtifact$StateMonitorSignal.signalSuccessfulCompletion(AbstractInstallArtifact.java:229)
at org.eclipse.virgo.kernel.core.internal.BundleStartTracker$1.run(BundleStartTracker.java:143)
at java.util.concurrent.ThreadPoolExecutor$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: org.eclipse.gemini.web.core.WebApplicationStartFailedException: org.eclipse.gemini.web.core.spi.ServletContainerException: Web application at '/greeter' failed to start. Check the logs for more details.
at org.eclipse.gemini.web.internal.StandardWebApplication.start(StandardWebApplication.java:108)
at org.eclipse.virgo.web.core.internal.WebBundleLifecycleListener.onStarted(WebBundleLifecycleListener.java:122)
... 8 common frames omitted
Caused by: org.eclipse.gemini.web.core.spi.ServletContainerException: Web application at '/greeter' failed to start. Check the logs for more details.
at org.eclipse.gemini.web.tomcat.internal.TomcatServletContainer.startWebApplication(TomcatServletContainer.java:125)
at org.eclipse.gemini.web.internal.StandardWebApplication.start(StandardWebApplication.java:91)
... 9 common frames omitted