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 11, 2016 10:21:04 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 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Server version:        Apache Tomcat/7.0.68
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Server built:          Feb 8 2016 20:25:54 UTC
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Server number:         7.0.68.0
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: OS Name:               Windows 7
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: OS Version:            6.1
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Architecture:          amd64
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Java Home:             D:Java_StudyJavajdk1.7.0_79jre
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: JVM Version:           1.7.0_79-b15
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: JVM Vendor:            Oracle Corporation
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: CATALINA_BASE:         D:Java_Studyworkspace.metadata.pluginsorg.eclipse.wst.server.core	mp0
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: CATALINA_HOME:         D:Java_Studyapache-tomcat-7.0.68
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dcatalina.base=D:Java_Studyworkspace.metadata.pluginsorg.eclipse.wst.server.core	mp0
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dcatalina.home=D:Java_Studyapache-tomcat-7.0.68
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dwtp.deploy=D:Java_Studyworkspace.metadata.pluginsorg.eclipse.wst.server.core	mp0webapps
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Djava.endorsed.dirs=D:Java_Studyapache-tomcat-7.0.68endorsed
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.VersionLoggerListener log
信息: Command line argument: -Dfile.encoding=UTF-8
五月 11, 2016 10:21:04 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_StudyJavajdk1.7.0_79in;C:WindowsSunJavain;C:Windowssystem32;C:Windows;D:/Java_Study/Java/jdk1.7.0_79/bin/../jre/bin/server;D:/Java_Study/Java/jdk1.7.0_79/bin/../jre/bin;D:/Java_Study/Java/jdk1.7.0_79/bin/../jre/lib/amd64;D:Java_StudyJavajdk1.7.0_79in;D:Java_StudyJavajdk1.7.0_79jrein;D:Java_Studymysql-5.7.12-winx64in;C:Windowssystem32;C:Windows;C:WindowsSystem32Wbem;C:WindowsSystem32WindowsPowerShellv1.0;C:Program Files (x86)Microsoft SQL Server100ToolsBinn;C:Program Files (x86)Microsoft SQL Server100DTSBinn;C:Program FilesMicrosoft SQL Server100ToolsBinn;C:Program FilesMicrosoft SQL Server100DTSBinn;C:Program Files (x86)Microsoft SQL Server100ToolsBinnVSShellCommon7IDE;C:Program Files (x86)Microsoft Visual Studio 9.0Common7IDEPrivateAssemblies;C:Program FilesMicrosoftWeb Platform Installer;C:Windowssystem32configsystemprofile.dnxin;C:Program FilesMicrosoft DNXDnvm;C:Program FilesMicrosoft SQL Server120ToolsBinn;C:Program Files (x86)Windows Kits10Windows Performance Toolkit;C:Program Files (x86)
odejs;D:Java_Studyapache-maven-3.3.9in;C:UsersAdministratorAppDataRoaming
pm;D:Java_Studyeclipse;;.
五月 11, 2016 10:21:04 下午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["http-bio-8080"]
五月 11, 2016 10:21:04 下午 org.apache.coyote.AbstractProtocol init
信息: Initializing ProtocolHandler ["ajp-bio-8009"]
五月 11, 2016 10:21:04 下午 org.apache.catalina.startup.Catalina load
信息: Initialization processed in 363 ms
五月 11, 2016 10:21:04 下午 org.apache.catalina.core.StandardService startInternal
信息: Starting service Catalina
五月 11, 2016 10:21:04 下午 org.apache.catalina.core.StandardEngine startInternal
信息: Starting Servlet Engine: Apache Tomcat/7.0.68
五月 11, 2016 10:21:05 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:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:188)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1120)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:819)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1572)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1562)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
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:153)
    ... 6 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:293)
    at org.apache.catalina.startup.ContextConfig.processAnnotationWebServlet(ContextConfig.java:2462)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsStream(ContextConfig.java:2137)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:2098)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:2090)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:2090)
    at org.apache.catalina.startup.ContextConfig.processAnnotationsFile(ContextConfig.java:2090)
    at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1304)
    at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:889)
    at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:386)
    at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
    at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
    at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5472)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    ... 6 more

五月 11, 2016 10:21:05 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:122)
    at java.util.concurrent.FutureTask.get(FutureTask.java:188)
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1120)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:300)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:444)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:738)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:693)
    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.apache.catalina.startup.Bootstrap.start(Bootstrap.java:294)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:428)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina].StandardHost[localhost]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1572)
    at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1562)
    at java.util.concurrent.FutureTask.run(FutureTask.java:262)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1128)
    at org.apache.catalina.core.StandardHost.startInternal(StandardHost.java:819)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    ... 6 more

五月 11, 2016 10:21:05 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[8005]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
    at org.apache.catalina.startup.Catalina.start(Catalina.java:693)
    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.apache.catalina.startup.Bootstrap.start(Bootstrap.java:294)
    at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:428)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
    at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:738)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    ... 7 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina]]
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:153)
    at org.apache.catalina.core.StandardService.startInternal(StandardService.java:444)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    ... 9 more
Caused by: org.apache.catalina.LifecycleException: A child container failed during start
    at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1128)
    at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:300)
    at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
    ... 11 more

五月 11, 2016 10:21:05 下午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["http-bio-8080"]
五月 11, 2016 10:21:05 下午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["ajp-bio-8009"]
五月 11, 2016 10:21:05 下午 org.apache.catalina.core.StandardService stopInternal
信息: Stopping service Catalina
五月 11, 2016 10:21:05 下午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["http-bio-8080"]
五月 11, 2016 10:21:05 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);        
    }
}