Java tomcat启动失败（Servlet3.0 Web Project）：A child container failed during start

Tomcat启动失败,失败全部信息：

五月 ,  :: 下午 org.apache.tomcat.util.digester.SetPropertiesRule begin
警告: [SetPropertiesRule]{Server/Service/Engine/Host/Context} Setting property 'source' to 'org.eclipse.jst.jee.server:MyEL' did not find a matching property.
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Server version:        Apache Tomcat/7.0.
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Server built:          Feb   :: UTC
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Server number:         7.0.68.0
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: OS Name:               Windows
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: OS Version:            6.1
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Architecture:          amd64
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Java Home:             D:\Java_Study\Java\jdk1..0_79\jre
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: JVM Version:           1.7.0_79-b15
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: JVM Vendor:            Oracle Corporation
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: CATALINA_BASE:         D:\Java_Study\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: CATALINA_HOME:         D:\Java_Study\apache-tomcat-7.0.
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dcatalina.base=D:\Java_Study\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dcatalina.home=D:\Java_Study\apache-tomcat-7.0.
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dwtp.deploy=D:\Java_Study\workspace\.metadata\.plugins\org.eclipse.wst.server.core\tmp0\webapps
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Djava.endorsed.dirs=D:\Java_Study\apache-tomcat-7.0.\endorsed
五月 ,  :: 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dfile.encoding=UTF-
五月 ,  :: 下午 org.apache.catalina.core.AprLifecycleListener lifecycleEvent
信息: The APR based Apache Tomcat Native library which allows optimal performance in production environments was not found on the java.library.path: D:\Java_Study\Java\jdk1..0_79\bin;C:\Windows\Sun\Java\bin;C:\Windows\system32;C:\Windows;D:/Java_Study/Java/jdk1..0_79/bin/../jre/bin/server;D:/Java_Study/Java/jdk1..0_79/bin/../jre/bin;D:/Java_Study/Java/jdk1..0_79/bin/../jre/lib/amd64;D:\Java_Study\Java\jdk1..0_79\bin;D:\Java_Study\Java\jdk1..0_79\jre\bin;D:\Java_Study\mysql-5.7.-winx64\bin;C:\Windows\system32;C:\Windows;C:\Windows\System32\Wbem;C:\Windows\System32\WindowsPowerShell\v1.\;C:\Program Files (x86)\Microsoft SQL Server\\Tools\Binn\;C:\Program Files (x86)\Microsoft SQL Server\\DTS\Binn\;C:\Program Files\Microsoft SQL Server\\Tools\Binn\;C:\Program Files\Microsoft SQL Server\\DTS\Binn\;C:\Program Files (x86)\Microsoft SQL Server\\Tools\Binn\VSShell\Common7\IDE\;C:\Program Files (x86)\Microsoft Visual Studio 9.0\Common7\IDE\PrivateAssemblies\;C:\Program Files\Microsoft\Web Platform Installer\;C:\Windows\system32\config\systemprofile\.dnx\bin;C:\Program Files\Microsoft DNX\Dnvm\;C:\Program Files\Microsoft SQL Server\\Tools\Binn\;C:\Program Files (x86)\Windows Kits\\Windows Performance Toolkit\;C:\Program Files (x86)\nodejs\;D:\Java_Study\apache-maven-3.3.\bin;C:\Users\Administrator\AppData\Roaming\npm;D:\Java_Study\eclipse;;.
五月 ,  :: 下午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["http-bio-8080"]
五月 ,  :: 下午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["ajp-bio-8009"]
五月 ,  :: 下午 org.apache.catalina.startup.Catalina load
信息: Initialization processed in  ms
五月 ,  :: 下午 org.apache.catalina.core.StandardService startInternal
信息: Starting service Catalina
五月 ,  :: 下午 org.apache.catalina.core.StandardEngine startInternal
信息: Starting Servlet Engine: Apache Tomcat/7.0.
五月 ,  :: 下午 org.apache.catalina.core.ContainerBase startInternal
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyEL]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:)
    at java.util.concurrent.FutureTask.get(FutureTask.java:)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:)
    at java.util.concurrent.FutureTask.run(FutureTask.java:)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:)
    at java.lang.Thread.run(Thread.java:)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost].StandardContext[/MyEL]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    ...  more
Caused by: java.lang.IllegalArgumentException: The servlets named [MyELServlet] and [com.dx.app.MyELServlet] are both mapped to the url-pattern [/MyELServlet] which is not permitted
    at org.apache.catalina.deploy.WebXml.addServletMapping(WebXml.java:)
    at org.apache.catalina.startup.ContextConfig.processAnnotationWebServlet(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    ...  more

五月 ,  :: 下午 org.apache.catalina.core.ContainerBase startInternal
严重: A child container failed during start
java.util.concurrent.ExecutionException: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at java.util.concurrent.FutureTask.report(FutureTask.java:)
    at java.util.concurrent.FutureTask.get(FutureTask.java:)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:)
    at java.lang.reflect.Method.invoke(Method.java:)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:)
    at java.util.concurrent.FutureTask.run(FutureTask.java:)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:)
    at java.lang.Thread.run(Thread.java:)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    ...  more

五月 ,  :: 下午 org.apache.catalina.startup.Catalina start
严重: The required Server component failed to start so Tomcat is unable to start.
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:)
    at java.lang.reflect.Method.invoke(Method.java:)
    at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    ...  more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    ...  more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:)
    ...  more

五月 ,  :: 下午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["http-bio-8080"]
五月 ,  :: 下午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["ajp-bio-8009"]
五月 ,  :: 下午 org.apache.catalina.core.StandardService stopInternal
信息: Stopping service Catalina
五月 ,  :: 下午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["http-bio-8080"]
五月 ,  :: 下午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["ajp-bio-8009"]

找到：/WEB-INF/web.xml

 <?xml version="1.0" encoding="UTF-8"?>
 <web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns="http://java.sun.com/xml/ns/javaee"
     xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
     id="WebApp_ID" version="3.0">
     <display-name>MyEL</display-name>
     <welcome-file-list>
         <welcome-file>default.jsp</welcome-file>
     </welcome-file-list>
10     <servlet>
11         <servlet-name>MyELServlet</servlet-name>
12         <servlet-class>com.dx.app.MyELServlet</servlet-class>
13     </servlet>
14     <servlet-mapping>
15         <servlet-name>MyELServlet</servlet-name>
16         <url-pattern>/MyELServlet</url-pattern>
17     </servlet-mapping>
 </web-app>

解决方案：

去掉其中的<servlet>标注信息

因为在Servlet类上边已经注解了servlet映射信息，所以不需要重复标注。

 package com.dx.app;

 import java.io.IOException;

 import javax.servlet.RequestDispatcher;
 import javax.servlet.ServletException;
 import javax.servlet.annotation.WebServlet;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 @WebServlet("/MyELServlet")
 public class MyELServlet extends HttpServlet {
     private static final long serialVersionUID = 1L;

     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
         response.getWriter().append("Served at: ").append(request.getContextPath());
         request.setAttribute("Hello", "Hello Servlet!");
         // 请求转发：
         // 1、调用HttpServletRequest 的getRequestDispatcher()的方法，获取RequestDispatcher对象
         // 调用getRequestDispatcher()需要传入转发的地址。
         String servletName="MyDispatcherServlet";
         RequestDispatcher requestDispatcher=request.getRequestDispatcher("/"+servletName);

         // 2、调用HttpServletRequest的forward(request,response)方法。
         requestDispatcher.forward(request, response);
     }
 }