请大家看看这个问题，小弟急啊！myeclipse+tomcat在tomcat启动时的错误！

Question

启动时就出现这个错误，麻烦看看下，能帮忙解决一下  ， 谢谢了！严重: Parse Error at line 6 column 52: Document root element "web-app", must match DOCTYPE root "null".
org.xml.sax.SAXParseException: Document root element "web-app", must match DOCTYPE root "null".
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
at org.apache.xerces.util.ErrorHandlerWrapper.error(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.rootElementSpecified(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.handleStartElement(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.startElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl$ContentDispatcher.scanRootElementHook(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.commons.digester.Digester.parse(Digester.java:1745)
at org.apache.catalina.startup.ContextConfig.applicationConfig(ContextConfig.java:221)
at org.apache.catalina.startup.ContextConfig.start(ContextConfig.java:580)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:182)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:3644)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:777)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:760)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:538)
at org.apache.catalina.core.StandardHostDeployer.install(StandardHostDeployer.java:261)
at org.apache.catalina.core.StandardHost.install(StandardHost.java:731)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:626)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:375)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:785)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:331)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1156)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:697)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1148)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:311)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:2213)
at org.apache.catalina.startup.Catalina.start(Catalina.java:459)
at org.apache.catalina.startup.Catalina.execute(Catalina.java:346)
at org.apache.catalina.startup.Catalina.process(Catalina.java:130)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:151)
2007-11-18 21:54:10 org.apache.commons.digester.Digester error
严重: Parse Error at line 6 column 52: Document is invalid: no grammar found.
org.xml.sax.SAXParseException: Document is invalid: no grammar found.
at org.apache.xerces.util.ErrorHandlerWrapper.createSAXParseException(Unknown Source)
at org.apache.xerces.util.ErrorHandlerWrapper.error(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.XMLErrorReporter.reportError(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.handleStartElement(Unknown Source)
at org.apache.xerces.impl.dtd.XMLDTDValidator.startElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElement(Unknown Source)
at org.apache.xerces.impl.XMLDocumentScannerImpl$ContentDispatcher.scanRootElementHook(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(Unknown Source)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XML11Configuration.parse(Unknown Source)
at org.apache.xerces.parsers.XMLParser.parse(Unknown Source)
at org.apache.xerces.parsers.AbstractSAXParser.parse(Unknown Source)
at org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.commons.digester.Digester.parse(Digester.java:1745)
at org.apache.catalina.startup.ContextConfig.applicationConfig(ContextConfig.java:221)
at org.apache.catalina.startup.ContextConfig.start(ContextConfig.java:580)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:182)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:3644)
at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:777)
at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:760)
at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:538)
at org.apache.catalina.core.StandardHostDeployer.install(StandardHostDeployer.java:261)
at org.apache.catalina.core.StandardHost.install(StandardHost.java:731)
at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:626)
at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:375)
at org.apache.catalina.startup.HostConfig.start(HostConfig.java:785)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:331)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:120)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1156)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:697)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1148)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:311)
at org.apache.catalina.core.StandardService.start(StandardService.java:450)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:2213)
at org.apache.catalina.startup.Catalina.start(Catalina.java:459)
at org.apache.catalina.startup.Catalina.execute(Catalina.java:346)
at org.apache.catalina.startup.Catalina.process(Catalina.java:130)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:324)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:151)

Answer 1

检查下web.xml是不是少写了什么东西

Answer 2

检查一下tomcat/conf/server.xml中对应用程序的配置，看看是否有改变过什么东西，用myeclips重新建立一个简单的工程，如果还不能正常启动的话，重新安装tomcat吧，建议尽量不要动tomcat目录下的文件，尤其的配置文件！！！

Answer 3

web.xml的头信息有问题,改成如下格式试试.<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">