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！

关于Eclipse导入maven项目报空指针异常的更多相关文章

  1. Eclipse 导入Maven 项目报错

    新建Maven项目时出错:org.apache.maven.archiver.MavenArchiver.getManifest   新建Maven项目时出错:org.apache.maven.arc ...

  2. eclipse怎么导入maven项目 eclipse导入maven项目详细教程

    转自:http://www.pc6.com/infoview/Article_114542.html Eclipse怎么导入maven项目一直是困扰着大量程序猿和刚上手小白们的问题,使用eclipse ...

  3. eclipse导入maven项目后依赖jar包更新问题->update project按钮

    eclipse导入maven项目后依赖jar包更新问题 1.eclipse有专门的导入maven项目按钮,file-import-maven project,eclipse会自动查找指定路径下的pom ...

  4. eclipse导入maven项目， A resource exists with a different case: '/xxx'.

    eclipse 导入maven 项目出现 这是由于你的workspace里有相同的项目, 这时在metadata里可以看到所有的project信息 只需在eclipse的package explore ...

  5. eclipse导入maven项目，资源文件位置显示不正确

    eclipse导入maven项目后,资源文件位置显示不正确,如下图所示 解决方法: 在resources上右键Build Path,选择Use as Source Folder即可正确显示资源文件

  6. Eclipse导入Maven项目出现错误：Unsupported IClasspathEntry kind=4

    使用Eclipse导入Maven项目失败,提示: An internal error occurred during: "Importing Maven projects". Un ...

  7. Eclipse导入Maven项目,使用server 启动报错，class 找不到，

    问题发现: 1.导入maven 项目后,用server 启动,选择项中没有这个项目 解决: 说明server 没有把该项目当成web项目,需要设置 项目右键 properties  ---- proj ...

  8. Eclipse导入Maven项目时class not found

    用maven开发javaweb项目可以自动导包,可以在配置文件pom.xml中发现依赖包,今天在eclipse中导入maven项目,开启tomcat服务器时报错 class not found, 看到 ...

  9. Eclipse导入servlet项目报错

    Eclipse导入servlet项目,缺少servlet的jar包,导致项目报错. 解决: step1:选中项目->properties step2:选择的Targeted Runtimes s ...

随机推荐

  1. spring 整合 servlet

    目的:记录spring整合 servlet过程demo.(企业实际开发中可能很少用到),融会贯通. 前言:在学习spring 过程(核心 ioc,aop,插一句 学了spring 才对这个有深刻概念, ...

  2. CodeMirror在线代码编辑器使用

    CodeMirror官网地址为:https://codemirror.net/ CodeMirror作为一款代码编辑器,其应用场景主要是在线网站写代码.如现在的leetcode.洛谷.code-vs等 ...

  3. session与cookie之间的关系

    一.客户端与服务端请求响应的关系 USER(客户端) 请求 tomcat(服务器), 属于HTTP请求.http请求是无状态的,即每次服务端接收到客户端的请求时,都是一个全新的请求,服务器并不知道客户 ...

  4. Calcite分析 - Rule

    Calcite源码分析,参考: http://matt33.com/2019/03/07/apache-calcite-process-flow/ https://matt33.com/2019/03 ...

  5. [转]Java 之 Serializable 序列化和反序列化的概念,作用的通俗易懂的解释

    原文地址:https://blog.csdn.net/qq_27093465/article/details/78544505 遇到这个 Java Serializable 序列化这个接口,我们可能会 ...

  6. 027_MacOs上如何将多页word打印到一个页面上

    工作中需要把word的多页面内容打印到同一张A4纸,所以就想了办法,首先word导出到pdf. 然后使用MacOs默认的PDF阅读器进行多页打印. 操作如下: 文件-打印布局选择每张纸需要打印的页数左 ...

  7. ThinkPHP5 基础知识入门 [入门必先了解]

    一.目录结构 下载最新版框架后,解压缩到web目录下面,可以看到初始的目录结构如下: project 应用部署目录 ├─application 应用目录(可设置) │ ├─common 公共模块目录( ...

  8. vmware装centos7 无法上网

    现象 使用ip address看不到ip地址 ping www.baidu.com无法ping通 解决方式: 1.设置网卡 vi /etc/sysconfig/network-scripts/ifcf ...

  9. Oracle系列五 多表查询

    笛卡尔集笛卡尔集会在下面条件下产生: 省略连接条件 连接条件无效 所有表中的所有行互相连接 为了避免笛卡尔集, 可以在 WHERE 加入有效的连接条件. Oracle 连接 使用连接在多个表中查询数据 ...

  10. 【WebSocket】WebSocket快速入门

    WebSocket介绍 WebSocket 是 HTML5 开始提供的一种在单个 TCP 连接上进行全双工通讯的协议. WebSocket 使得客户端和服务器之间的数据交换变得更加简单,允许服务端主动 ...