Cannot create text hover for my editor in Eclipse plugin development
<p>In Eclipse plugin development, I customerize an editor which extends the <code>CompilationUnitEditor</code>, a customized source viewer named <code>CLRJavaSourceViewer</code>, which implements <code>IJavaEditorTextHover</code>. 
In the plugin.xml, I create an extension on org.eclipse.jdt.ui.javaEditorTextHover as</p>

<p><a href="http://i.stack.imgur.com/6oUIE.png" rel="nofollow">plugin.xml</a>
Errors in creating a text hover for my own editor.    </p>

<pre><code>java.lang.ClassCastException: loongplugin.editor.viewer.CLRJavaSourceViewer cannot be cast to org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor$AdaptedSourceViewer
    at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor.handlePreferenceStoreChanged(CompilationUnitEditor.java:1573)
    at org.eclipse.ui.texteditor.AbstractTextEditor$PropertyChangeListener.propertyChange(AbstractTextEditor.java:715)
    at org.eclipse.ui.texteditor.ChainedPreferenceStore.firePropertyChangeEvent(ChainedPreferenceStore.java:164)
    at org.eclipse.ui.texteditor.ChainedPreferenceStore.handlePropertyChangeEvent(ChainedPreferenceStore.java:431)
    at org.eclipse.ui.texteditor.ChainedPreferenceStore.access$0(ChainedPreferenceStore.java:408)
    at org.eclipse.ui.texteditor.ChainedPreferenceStore$PropertyChangeListener.propertyChange(ChainedPreferenceStore.java:69)
    at org.eclipse.ui.preferences.ScopedPreferenceStore$3.run(ScopedPreferenceStore.java:382)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.preferences.ScopedPreferenceStore.firePropertyChangeEvent(ScopedPreferenceStore.java:378)
    at org.eclipse.ui.preferences.ScopedPreferenceStore$2.preferenceChange(ScopedPreferenceStore.java:197)
    at org.eclipse.core.internal.preferences.EclipsePreferences$3.run(EclipsePreferences.java:896)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.core.internal.preferences.EclipsePreferences.firePreferenceEvent(EclipsePreferences.java:899)
    at org.eclipse.core.internal.preferences.EclipsePreferences.put(EclipsePreferences.java:912)
    at org.eclipse.ui.preferences.ScopedPreferenceStore.setValue(ScopedPreferenceStore.java:824)
    at org.eclipse.jdt.internal.ui.preferences.OverlayPreferenceStore.propagateProperty(OverlayPreferenceStore.java:139)
    at org.eclipse.jdt.internal.ui.preferences.OverlayPreferenceStore.propagate(OverlayPreferenceStore.java:146)
    at org.eclipse.jdt.internal.ui.preferences.AbstractConfigurationBlockPreferencePage.performOk(AbstractConfigurationBlockPreferencePage.java:98)
    at org.eclipse.jface.preference.PreferenceDialog$12.run(PreferenceDialog.java:992)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:50)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:178)
    at org.eclipse.jface.preference.PreferenceDialog.okPressed(PreferenceDialog.java:971)
    at org.eclipse.ui.internal.dialogs.FilteredPreferenceDialog.okPressed(FilteredPreferenceDialog.java:460)
    at org.eclipse.ui.internal.dialogs.WorkbenchPreferenceDialog.okPressed(WorkbenchPreferenceDialog.java:174)
    at org.eclipse.jface.preference.PreferenceDialog.buttonPressed(PreferenceDialog.java:236)
    at org.eclipse.jface.dialogs.Dialog$2.widgetSelected(Dialog.java:619)
    at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:248)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4188)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1467)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1490)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1475)
    at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1279)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4031)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3658)
    at org.eclipse.jface.window.Window.runEventLoop(Window.java:832)
    at org.eclipse.jface.window.Window.open(Window.java:808)
    at org.eclipse.ui.internal.dialogs.WorkbenchPreferenceDialog.open(WorkbenchPreferenceDialog.java:221)
    at org.eclipse.ui.texteditor.AbstractDecoratedTextEditor$9.run(AbstractDecoratedTextEditor.java:1259)
    at org.eclipse.jface.action.Action.runWithEvent(Action.java:519)
    at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:595)
    at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:511)
    at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:420)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4188)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1467)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1490)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1475)
    at org.eclipse.swt.widgets.Widget.notifyListeners(Widget.java:1279)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4031)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3658)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1151)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1032)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:148)
    at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:636)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:579)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
    at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:135)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:382)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:236)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:648)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:603)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1438)
</code></pre>