title: Problems occurred when invoking code from plug-in: "org.eclipse.core.resources"
body: <p>I have integrated gwt with Hibernate but when I creating hibernate.reveng.xml, I have an error and I couldn't entity bean class.The error mesage ; </p>
  
  <p>Problems occurred when invoking code from plug-in: "org.eclipse.core.resources".[enter link description here][1]</p>
  
  <pre><code>java.lang.NullPointerException
  at org.jboss.ide.eclipse.archives.core.WorkspaceChangeListener$2.visit(WorkspaceChangeListener.java:74)
  at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:69)
  at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:49)
  at org.jboss.ide.eclipse.archives.core.WorkspaceChangeListener.resourceChanged(WorkspaceChangeListener.java:70)
  at org.eclipse.core.internal.events.NotificationManager$1.run(NotificationManager.java:291)
  at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
  at org.eclipse.core.internal.events.NotificationManager.notify(NotificationManager.java:285)
  at org.eclipse.core.internal.events.NotificationManager.broadcastChanges(NotificationManager.java:149)
  at org.eclipse.core.internal.resources.Workspace.broadcastPostChange(Workspace.java:395)
  at org.eclipse.core.internal.resources.Workspace.checkpoint(Workspace.java:557)
  at org.eclipse.ltk.core.refactoring.PerformChangeOperation$1.run(PerformChangeOperation.java:263)
  at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2344)
  at org.eclipse.ltk.core.refactoring.PerformChangeOperation.executeChange(PerformChangeOperation.java:306)
  at org.eclipse.ltk.internal.ui.refactoring.UIPerformChangeOperation.executeChange(UIPerformChangeOperation.java:92)
  at org.eclipse.ltk.core.refactoring.PerformChangeOperation.run(PerformChangeOperation.java:218)
  at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2344)
  at org.eclipse.ltk.internal.ui.refactoring.WorkbenchRunnableAdapter.run(WorkbenchRunnableAdapter.java:87)
  at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:121)
  </code></pre>