.log内容如下：
!ENTRY org.eclipse.ui 4 4 2017-04-14 09:31:05.341
!MESSAGE An internal error has occurred.
!STACK 0
java.lang.NullPointerException
at org.eclipse.ui.internal.WorkbenchPage.busyShowView(WorkbenchPage.java:1270)
at org.eclipse.ui.internal.WorkbenchPage$12.run(WorkbenchPage.java:4211)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.ui.internal.WorkbenchPage.showView(WorkbenchPage.java:4207)
at org.eclipse.ui.internal.console.ConsoleManager$ShowConsoleViewJob.runInUIThread(ConsoleManager.java:321)
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:135)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4155)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3772)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$4.run(PartRenderingEngine.java:1127)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1018)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:156)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:654)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:337)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:598)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:139)
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(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:669)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:608)
at org.eclipse.equinox.launcher.Main.run(Main.java:1515)
at org.eclipse.equinox.launcher.Main.main(Main.java:1488)
!SESSION 2017-04-14 09:35:52.704 -----------------------------------------------
eclipse.buildId=4.5.0.I20150603-2000
java.version=1.7.0_75
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=zh_CN
Framework arguments: -product org.eclipse.epp.package.jee.product
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product
--------------------------------------------------------------分割线------------------------------------------------------
在网上查找了很多很多方法，包括删除.log文件、.settings文件、取消validation等等都不好使。后来看到有说删除D:\eclipse-jee-mars-R-win32-x86_64\workspace\.metadata\.plugins\org.eclipse.e4.workbench\workbench.xmi的。一试见效。
副作用：关于工作集之类的个性化设置会消失。