title: Deployment Assembly: The currently displayed page contains invalid values
body: <p>I imported a Java Web application from Sourceforge, and I did three working weeks efforts to get rid off all red crosses attached to the project name and packages, but now I couldn't make the application run on my Eclipse &amp; tomcat6 developing environment. In project properties when I tried to set the Deployment Assembly, the dialog box showed: the currently displayed page contains invalid values. And in the error log, I found when I click the Deployment Assembly, The following error message was showed:</p>
  
  <p>Error</p>
  
  <pre><code>
  Wed Jan 09 10:25:16 CST 2013
  Problems occurred when invoking code from plug-in: "org.eclipse.jface".
  
  java.lang.NullPointerException
      at org.eclipse.wst.common.componentcore.internal.resources.VirtualFolder.getFirstTaggedResource(VirtualFolder.java:185)
      at org.eclipse.jst.j2ee.componentcore.J2EEModuleVirtualComponent.getDefaultDeploymentDescriptorFolder(J2EEModuleVirtualComponent.java:542)
      at org.eclipse.jst.j2ee.internal.ui.JavaEEDeploymentAssemblyAdvancedSectionBuilder.(JavaEEDeploymentAssemblyAdvancedSectionBuilder.java:86)
      at org.eclipse.jst.j2ee.internal.ui.J2EEModuleDependenciesPropertyPage.getAdvancedSectionBuilder(J2EEModuleDependenciesPropertyPage.java:381)
      at org.eclipse.jst.j2ee.internal.ui.J2EEModuleDependenciesPropertyPage.(J2EEModuleDependenciesPropertyPage.java:65)
      at org.eclipse.jst.servlet.ui.internal.WebDependencyPropertyPage.(WebDependencyPropertyPage.java:34)
      at org.eclipse.jst.servlet.ui.internal.WebModuleDependencyPageProvider.createPages(WebModuleDependencyPageProvider.java:54)
      at org.eclipse.wst.common.componentcore.ui.propertypage.ModuleAssemblyRootPage.createContents(ModuleAssemblyRootPage.java:195)
      at org.eclipse.jface.preference.PreferencePage.createControl(PreferencePage.java:232)
      at org.eclipse.wst.common.componentcore.ui.propertypage.ModuleAssemblyRootPage.createControl(ModuleAssemblyRootPage.java:346)
      at org.eclipse.jface.preference.PreferenceDialog.createPageControl(PreferenceDialog.java:1502)
      at org.eclipse.jface.preference.PreferenceDialog$14.run(PreferenceDialog.java:1259)
      at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
      at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
      at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
      at org.eclipse.jface.preference.PreferenceDialog.showPage(PreferenceDialog.java:1253)
      at org.eclipse.ui.internal.dialogs.FilteredPreferenceDialog.showPage(FilteredPreferenceDialog.java:675)
      at org.eclipse.jface.preference.PreferenceDialog$10.run(PreferenceDialog.java:709)
      at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
      at org.eclipse.jface.preference.PreferenceDialog$9.selectionChanged(PreferenceDialog.java:705)
      at org.eclipse.jface.viewers.StructuredViewer$3.run(StructuredViewer.java:888)
      at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
      at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
      at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
      at org.eclipse.jface.viewers.StructuredViewer.firePostSelectionChanged(StructuredViewer.java:886)
      at org.eclipse.jface.viewers.StructuredViewer.handlePostSelect(StructuredViewer.java:1226)
      at org.eclipse.jface.viewers.StructuredViewer$5.widgetSelected(StructuredViewer.java:1251)
      at org.eclipse.jface.util.OpenStrategy.firePostSelectionEvent(OpenStrategy.java:262)
      at org.eclipse.jface.util.OpenStrategy.access$5(OpenStrategy.java:256)
      at org.eclipse.jface.util.OpenStrategy$3.run(OpenStrategy.java:433)
      at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
      at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:135)
      at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4144)
      at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3761)
      at org.eclipse.jface.window.Window.runEventLoop(Window.java:825)
      at org.eclipse.jface.window.Window.open(Window.java:801)
      at org.eclipse.ui.dialogs.PropertyDialogAction.run(PropertyDialogAction.java:158)
      at org.eclipse.jface.action.Action.runWithEvent(Action.java:498)
      at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
      at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
      at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
      at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
      at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
      at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4169)
      at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3758)
      at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1022)
      at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
      at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:916)
      at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:86)
      at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:585)
      at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
      at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:540)
      at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
      at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
      at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
      at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
      at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
      at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
      at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
      at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
      at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
      at org.eclipse.equinox.launcher.Main.main(Main.java:1414)
  </code></pre>
  
  <p>I googled many times , but I cannot find the solutions. Can anyone give a favor to let the Deployment Assembly work? I think this is the key why my app cannot run. Thanks in advance.    </p>