前言：
前幾天，使用idea導入一個eclipse項目，先是找不到jar包，於是設置完成以後，jar算是找到了。
但是啓動報錯org.apache.catalina.deploy.WebXml addFilter，網上有很多說是jar衝突的，費了老半天勁，終於找到一篇正解文章。本文參考： http://blog.csdn.net/qq525099302/article/details/43486889
報錯信息：
嚴重: End event threw exception
java.lang.NoSuchMethodException: org.apache.catalina.deploy.WebXml addFilter
at org.apache.tomcat.util.IntrospectionUtils.callMethod1(IntrospectionUtils.java:849)
at org.apache.tomcat.util.digester.SetNextRule.end(SetNextRule.java:201)
at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:1063)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1561)
at org.apache.catalina.startup.ContextConfig.parseWebXml(ContextConfig.java:1812)
at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1250)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:876)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:374)
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:5355)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
二月 04, 2015 3:22:13 下午 org.apache.catalina.startup.ContextConfig parseWebXml
嚴重: Parse error in application web.xml file at jndi:/localhost/app1/WEB-INF/web.xml
org.xml.sax.SAXParseException; systemId: jndi:/localhost/app1/WEB-INF/web.xml; lineNumber: 27; columnNumber: 14; Error at (27, 14) : org.apache.catalina.deploy.WebXml addFilter
at org.apache.tomcat.util.digester.Digester.createSAXException(Digester.java:2711)
at org.apache.tomcat.util.digester.Digester.createSAXException(Digester.java:2743)
at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:1066)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.endElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanEndElement(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.apache.tomcat.util.digester.Digester.parse(Digester.java:1561)
at org.apache.catalina.startup.ContextConfig.parseWebXml(ContextConfig.java:1812)
at org.apache.catalina.startup.ContextConfig.webConfig(ContextConfig.java:1250)
at org.apache.catalina.startup.ContextConfig.configureStart(ContextConfig.java:876)
at org.apache.catalina.startup.ContextConfig.lifecycleEvent(ContextConfig.java:374)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5355)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1559)
at org.apache.catalina.core.ContainerBase$StartChild.call(ContainerBase.java:1549)
at java.util.concurrent.FutureTask.run(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.NoSuchMethodException: org.apache.catalina.deploy.WebXml addFilter
at org.apache.tomcat.util.IntrospectionUtils.callMethod1(IntrospectionUtils.java:849)
at org.apache.tomcat.util.digester.SetNextRule.end(SetNextRule.java:201)
at org.apache.tomcat.util.digester.Digester.endElement(Digester.java:1063)
... 25 more解決辦法：找到tomcat下的 conf/content.xml
找到tomcat下的 conf文件夾下的content.xml,在<Context></Context>中添加 <Loader delegate="true"/>
重新啓動，完美解決！
原因分析：
<Loader delegate="true"/>
True，表示tomcat將遵循JVM的delegate機制，即一個WebAppClassLoader在加載類文件 時，會先遞交給SharedClassLoader加載，
SharedClassLoader無法加載成功，會繼續向自己的父類委託，一直到BootstarpClassLoader，如果都沒有加載成功，
則最後由WebAppClassLoader自己進行加載。
False，表示將不遵循這個delegate機制，即WebAppClassLoader在加載類文件時，會優先自己嘗試加載，
如果加載失敗，纔會沿着繼承鏈，依次委託父類加載。
