Major Following Ticket Monster example (http://www.jboss.org/ticket-monster/introduction/), I created an Event entity from Forge wizard. I got the following error in the Log when (or just after) the notification bubble appeared:
java.lang.NullPointerException at org.eclipse.jpt.jpa.core.internal.AbstractJpaProject.compilationUnitResourceExists(AbstractJpaProject.java:1436) at org.eclipse.jpt.jpa.core.internal.AbstractJpaProject.javaCompilationUnitDeltaIsRelevant(AbstractJpaProject.java:1425) at org.eclipse.jpt.jpa.core.internal.InternalJpaProjectManager.javaCompilationUnitDeltaIsRelevant(InternalJpaProjectManager.java:1006) at org.eclipse.jpt.jpa.core.internal.InternalJpaProjectManager.handleJavaCompilationUnitDelta(InternalJpaProjectManager.java:998) at org.eclipse.jpt.jpa.core.internal.InternalJpaProjectManager.handleJavaDelta(InternalJpaProjectManager.java:933) at org.eclipse.jpt.jpa.core.internal.InternalJpaProjectManager.handleJavaElementChangedEvent(InternalJpaProjectManager.java:916) at org.eclipse.jpt.jpa.core.internal.InternalJpaProjectManager.javaElementChanged(InternalJpaProjectManager.java:859) at org.eclipse.jpt.jpa.core.internal.InternalJpaProjectManager$JavaElementChangeListener.elementChanged(InternalJpaProjectManager.java:1389) at org.eclipse.jdt.internal.core.DeltaProcessor$4.run(DeltaProcessor.java:1695) at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42) at org.eclipse.jdt.internal.core.DeltaProcessor.notifyListeners(DeltaProcessor.java:1685) at org.eclipse.jdt.internal.core.DeltaProcessor.fireReconcileDelta(DeltaProcessor.java:1537) at org.eclipse.jdt.internal.core.DeltaProcessor.fire(DeltaProcessor.java:1496) at org.eclipse.jdt.internal.core.JavaModelOperation.run(JavaModelOperation.java:770) at org.eclipse.jdt.internal.core.JavaModelOperation.runOperation(JavaModelOperation.java:789) at org.eclipse.jdt.internal.core.CompilationUnit.reconcile(CompilationUnit.java:1269) at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.reconcile(JavaReconcilingStrategy.java:126) at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.access$0(JavaReconcilingStrategy.java:108) at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy$1.run(JavaReconcilingStrategy.java:89) at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42) at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.reconcile(JavaReconcilingStrategy.java:87) at org.eclipse.jdt.internal.ui.text.java.JavaReconcilingStrategy.initialReconcile(JavaReconcilingStrategy.java:178) at org.eclipse.jdt.internal.ui.text.CompositeReconcilingStrategy.initialReconcile(CompositeReconcilingStrategy.java:114) at org.eclipse.jdt.internal.ui.text.JavaCompositeReconcilingStrategy.initialReconcile(JavaCompositeReconcilingStrategy.java:141) at org.eclipse.jface.text.reconciler.MonoReconciler.initialProcess(MonoReconciler.java:105) at org.eclipse.jdt.internal.ui.text.JavaReconciler.initialProcess(JavaReconciler.java:406) at org.eclipse.jface.text.reconciler.AbstractReconciler$BackgroundThread.run(AbstractReconciler.java:173)
Not sure if it's related to Forge or Eclipse JPA tooling (in which case, it would be an upstream bug, I guess).
