解决：eclipse 非正常关闭，导致无法正常启动

eclipse 无法正常启动：

!ENTRY org.eclipse.ui.navigator 4 2 2016-09-07 11:23:54.181
!MESSAGE 从插件调用代码时出现问题：“org.eclipse.ui.navigator”。
!STACK 0
java.lang.NullPointerException
    at org.eclipse.jpt.common.ui.internal.jface.ItemTreeStateProviderManager.getChildren(ItemTreeStateProviderManager.java:74)
    at org.eclipse.jpt.common.ui.internal.navigator.NavigatorContentProvider.getChildren(NavigatorContentProvider.java:109)
    at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:96)
    at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:275)
    at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:94)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider$1.run(NavigatorContentServiceContentProvider.java:152)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider.internalGetChildren(NavigatorContentServiceContentProvider.java:139)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider.getChildren(NavigatorContentServiceContentProvider.java:125)
    at org.eclipse.jface.viewers.AbstractTreeViewer.getRawChildren(AbstractTreeViewer.java:1365)
    at org.eclipse.jface.viewers.TreeViewer.getRawChildren(TreeViewer.java:353)
    at org.eclipse.jface.viewers.StructuredViewer.getFilteredChildren(StructuredViewer.java:905)
    at org.eclipse.jface.viewers.AbstractTreeViewer.getSortedChildren(AbstractTreeViewer.java:617)
    at org.eclipse.jface.viewers.AbstractTreeViewer.updateChildren(AbstractTreeViewer.java:2647)
    at org.eclipse.jface.viewers.AbstractTreeViewer.internalRefreshStruct(AbstractTreeViewer.java:1918)
    at org.eclipse.jface.viewers.TreeViewer.internalRefreshStruct(TreeViewer.java:684)
    at org.eclipse.jface.viewers.AbstractTreeViewer.internalRefresh(AbstractTreeViewer.java:1893)
    at org.eclipse.jface.viewers.AbstractTreeViewer.internalRefresh(AbstractTreeViewer.java:1850)
    at org.eclipse.ui.navigator.CommonViewer.internalRefresh(CommonViewer.java:561)
    at org.eclipse.jface.viewers.StructuredViewer$8.run(StructuredViewer.java:1528)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1436)
    at org.eclipse.jface.viewers.TreeViewer.preservingSelection(TreeViewer.java:366)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1397)
    at org.eclipse.jface.viewers.StructuredViewer.refresh(StructuredViewer.java:1525)
    at org.eclipse.jface.viewers.ColumnViewer.refresh(ColumnViewer.java:533)
    at org.eclipse.ui.navigator.CommonViewer.refresh(CommonViewer.java:350)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerContentProvider$3.run(PackageExplorerContentProvider.java:957)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerContentProvider.runUpdates(PackageExplorerContentProvider.java:195)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerContentProvider.runPendingUpdates(PackageExplorerContentProvider.java:187)
    at org.eclipse.jdt.internal.ui.packageview.PackageExplorerContentProvider$1.runInUIThread(PackageExplorerContentProvider.java:165)
    at org.eclipse.ui.progress.UIJob$1.run(UIJob.java:97)
    at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
    at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:136)
    at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4147)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3764)
    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:380)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:235)
    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)

!ENTRY org.eclipse.ui.navigator 4 0 2016-09-07 11:23:54.184
!MESSAGE 调用扩展时发生了异常：对象 P/* 的 org.eclipse.jpt.jpa.ui.jpaNavigatorContent
!STACK 0
java.lang.NullPointerException
    at org.eclipse.jpt.common.ui.internal.jface.ItemTreeStateProviderManager.getChildren(ItemTreeStateProviderManager.java:74)
    at org.eclipse.jpt.common.ui.internal.navigator.NavigatorContentProvider.getChildren(NavigatorContentProvider.java:109)
    at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:96)
    at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:275)
    at org.eclipse.ui.internal.navigator.extensions.SafeDelegateTreeContentProvider.getChildren(SafeDelegateTreeContentProvider.java:94)
    at org.eclipse.ui.internal.navigator.NavigatorContentServiceContentProvider$1.run(NavigatorContentServiceContentProvider.java:152)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)

打开eclipse的工作空间目录workspace，然后进入目录 workspace\.metadata\.plugins\org.eclipse.core.resources删掉.snap 文件......