今天新建了一个maven项目，因为是通过公司的工具新建的，代码拉下来就有src、pom.xml文件。
导入Eclipse却报空指针异常。具体如下：
An error has occurred. See error log for more details.
java.lang.NullPointerException
一时没看明白是为什么，搜了一下Eclipse的日志文件。
日志在workSpace的.metadata里的.log文件。
点开查看，如下：
!SESSION 2019-09-16 14:31:23.461 -----------------------------------------------
eclipse.buildId=4.7.3.M20180330-0640
java.version=1.8.0_144
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
!ENTRY org.eclipse.egit.ui 2 0 2019-09-16 14:31:42.700
!MESSAGE Warning: The environment variable HOME is not set. The following directory will be used to store the Git
user global configuration and to define the default location to store repositories: 'C:\Users\flyin'. If this is
not correct please set the HOME environment variable and restart Eclipse. Otherwise Git for Windows and
EGit might behave differently since they see different configuration options.
This warning can be switched off on the Team > Git > Confirmations and Warnings preference page.
!ENTRY org.eclipse.epp.logging.aeri.ide 2 17 2019-09-16 14:31:53.542
!MESSAGE Server ‘org.eclipse.epp.logging.aeri.ide.server’ failed with exception: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $. ; version: 2.0.7.v20170906-1327
!STACK 0
com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:224)
at com.google.gson.Gson.fromJson(Gson.java:887)
at com.google.gson.Gson.fromJson(Gson.java:852)
at com.google.gson.Gson.fromJson(Gson.java:801)
at org.eclipse.epp.internal.logging.aeri.ide.server.json.Json.deserialize(Json.java:91)
at org.eclipse.epp.internal.logging.aeri.ide.server.mars.IO.refreshConfiguration(IO.java:66)
at org.eclipse.epp.internal.logging.aeri.ide.server.mars.ServerConnection.startUp(ServerConnection.java:124)
at com.google.common.util.concurrent.AbstractIdleService$DelegateService$1.run(AbstractIdleService.java:62)
at com.google.common.util.concurrent.Callables$4.run(Callables.java:122)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was STRING at line 1 column 1 path $
at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:385)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:213)
... 9 more
!ENTRY org.eclipse.jface 4 2 2019-09-16 14:33:23.521
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
java.lang.NullPointerException
at org.eclipse.m2e.core.project.ProjectImportConfiguration.cleanProjectNameComponent(ProjectImportConfiguration.java:109)
at org.eclipse.m2e.core.project.ProjectImportConfiguration.getProjectName(ProjectImportConfiguration.java:83)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage.isAlreadyExists(MavenImportWizardPage.java:615)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage$ProjectLabelProvider.getForeground(MavenImportWizardPage.java:812)
at org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider.getForeground(DelegatingStyledCellLabelProvider.java:140)
at org.eclipse.jface.viewers.DelegatingStyledCellLabelProvider.update(DelegatingStyledCellLabelProvider.java:123)
at org.eclipse.jface.viewers.ViewerColumn.refresh(ViewerColumn.java:141)
at org.eclipse.jface.viewers.AbstractTreeViewer.doUpdateItem(AbstractTreeViewer.java:946)
at org.eclipse.jface.viewers.CheckboxTreeViewer.doUpdateItem(CheckboxTreeViewer.java:120)
at org.eclipse.jface.viewers.AbstractTreeViewer$UpdateItemSafeRunnable.run(AbstractTreeViewer.java:117)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.ui.internal.JFaceUtil.lambda$0(JFaceUtil.java:44)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:173)
at org.eclipse.jface.viewers.AbstractTreeViewer.doUpdateItem(AbstractTreeViewer.java:1025)
at org.eclipse.jface.viewers.StructuredViewer$UpdateItemSafeRunnable.run(StructuredViewer.java:475)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.ui.internal.JFaceUtil.lambda$0(JFaceUtil.java:44)
at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:173)
at org.eclipse.jface.viewers.StructuredViewer.updateItem(StructuredViewer.java:2159)
at org.eclipse.jface.viewers.AbstractTreeViewer.createTreeItem(AbstractTreeViewer.java:840)
at org.eclipse.jface.viewers.AbstractTreeViewer.lambda$0(AbstractTreeViewer.java:817)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:792)
at org.eclipse.jface.viewers.TreeViewer.createChildren(TreeViewer.java:595)
at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:763)
at org.eclipse.jface.viewers.AbstractTreeViewer.internalInitializeTree(AbstractTreeViewer.java:1527)
at org.eclipse.jface.viewers.TreeViewer.internalInitializeTree(TreeViewer.java:771)
at org.eclipse.jface.viewers.AbstractTreeViewer.lambda$1(AbstractTreeViewer.java:1512)
at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1447)
at org.eclipse.jface.viewers.TreeViewer.preservingSelection(TreeViewer.java:354)
at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1408)
at org.eclipse.jface.viewers.CheckboxTreeViewer.preservingSelection(CheckboxTreeViewer.java:403)
at org.eclipse.jface.viewers.AbstractTreeViewer.inputChanged(AbstractTreeViewer.java:1506)
at org.eclipse.jface.viewers.ContentViewer.setInput(ContentViewer.java:286)
at org.eclipse.jface.viewers.StructuredViewer.setInput(StructuredViewer.java:1685)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage.scanProjects(MavenImportWizardPage.java:465)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage$1.widgetSelected(MavenImportWizardPage.java:183)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:249)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:86)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4428)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4238)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3817)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:818)
at org.eclipse.jface.window.Window.open(Window.java:794)
at org.eclipse.ui.internal.handlers.WizardHandler$Import.executeHandler(WizardHandler.java:158)
at org.eclipse.ui.internal.handlers.WizardHandler.execute(WizardHandler.java:290)
at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:291)
at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(E4HandlerProxy.java:92)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55)
at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:305)
at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:239)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:132)
at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(HandlerServiceHandler.java:152)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:494)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:487)
at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:210)
at org.eclipse.ui.internal.handlers.LegacyHandlerService.executeCommand(LegacyHandlerService.java:390)
at org.eclipse.ui.internal.actions.CommandAction.runWithEvent(CommandAction.java:151)
at org.eclipse.ui.internal.actions.CommandAction.run(CommandAction.java:161)
at org.eclipse.ui.actions.ImportResourcesAction.run(ImportResourcesAction.java:99)
at org.eclipse.ui.actions.BaseSelectionListenerAction.runWithEvent(BaseSelectionListenerAction.java:167)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:565)
at org.eclipse.jface.action.ActionContributionItem.lambda$4(ActionContributionItem.java:397)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:86)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4428)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4238)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3817)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1150)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1039)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:680)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:594)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
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:388)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:653)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:590)
at org.eclipse.equinox.launcher.Main.run(Main.java:1499)
!ENTRY org.eclipse.ui 4 0 2019-09-16 14:33:23.656
!MESSAGE Unhandled event loop exception
!STACK 0
java.lang.NullPointerException
at org.eclipse.m2e.core.project.ProjectImportConfiguration.cleanProjectNameComponent(ProjectImportConfiguration.java:109)
at org.eclipse.m2e.core.project.ProjectImportConfiguration.getProjectName(ProjectImportConfiguration.java:83)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage.isAlreadyExists(MavenImportWizardPage.java:615)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage.updateCheckedState(MavenImportWizardPage.java:592)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage.setAllChecked(MavenImportWizardPage.java:582)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage.scanProjects(MavenImportWizardPage.java:468)
at org.eclipse.m2e.core.ui.internal.wizards.MavenImportWizardPage$1.widgetSelected(MavenImportWizardPage.java:183)
at org.eclipse.swt.widgets.TypedListener.handleEvent(TypedListener.java:249)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:86)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4428)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4238)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3817)
at org.eclipse.jface.window.Window.runEventLoop(Window.java:818)
at org.eclipse.jface.window.Window.open(Window.java:794)
at org.eclipse.ui.internal.handlers.WizardHandler$Import.executeHandler(WizardHandler.java:158)
at org.eclipse.ui.internal.handlers.WizardHandler.execute(WizardHandler.java:290)
at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:291)
at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(E4HandlerProxy.java:92)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55)
at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:305)
at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:239)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:132)
at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(HandlerServiceHandler.java:152)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:494)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:487)
at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:210)
at org.eclipse.ui.internal.handlers.LegacyHandlerService.executeCommand(LegacyHandlerService.java:390)
at org.eclipse.ui.internal.actions.CommandAction.runWithEvent(CommandAction.java:151)
at org.eclipse.ui.internal.actions.CommandAction.run(CommandAction.java:161)
at org.eclipse.ui.actions.ImportResourcesAction.run(ImportResourcesAction.java:99)
at org.eclipse.ui.actions.BaseSelectionListenerAction.runWithEvent(BaseSelectionListenerAction.java:167)
at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:565)
at org.eclipse.jface.action.ActionContributionItem.lambda$4(ActionContributionItem.java:397)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:86)
at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4428)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1079)
at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4238)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3817)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1150)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1039)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:680)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:336)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:594)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:148)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:151)
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:388)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:243)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:653)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:590)
at org.eclipse.equinox.launcher.Main.run(Main.java:1499)
!ENTRY org.eclipse.m2e.logback.appender 2 0 2019-09-16 14:38:53.596
!MESSAGE Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
!ENTRY org.eclipse.m2e.logback.appender 2 0 2019-09-16 14:38:53.680
!MESSAGE Using platform encoding (GBK actually) to copy filtered resources, i.e. build is platform dependent!
搜了一圈，说是Eclipse的插件问题导致的，可以把“.metadata”这个文件夹删掉，代价是项目需要重新导入。
我删了，依然不行。
另外，不仅项目项目需要重新导入，Eclipse配置也全部还原了。
无计可施的时候，我对比了一下之前的文件，发现pom.xml里少配了一些东西。
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<properties>
……
正常的项目这部分是下面这样的：
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.shuimutong</groupId>
<artifactId>testw</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>testwMavenWebapp</name>
<url>http://maven.apache.org</url>
<properties>
……
把配置补全，导入成功！