今天在测试单点登录，需要tomcat 下发布多项目，tomcat报如下错误,
在网上收到好多回答，几乎是人云亦云，很多，我总结了一下，主要是jar包冲突造成的，我们只需要把项目中lib下的xerces.jar
删除即可。
Unable to load configuration. - [unknown location] at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.Java:69) at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:371) at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:415) at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:190) at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:275) at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:397) at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:108) at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3800) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4450) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:526) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:987) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:909) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:495) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1206) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:314) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053) at org.apache.catalina.core.StandardHost.start(StandardHost.java:722) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:583) 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:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413) Caused by: Caught exception while loading file struts-default.xml - [unknown location] at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:913) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:154) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:121) at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:179) at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66) ... 30 more Caused by: java.lang.ClassCastException: org.apache.xerces.parsers.XML11Configuration cannot be cast to org.apache.xerces.xni.parser.XMLParserConfiguration at org.apache.xerces.parsers.DOMParser.<init>(Unknown Source) at org.apache.xerces.parsers.DOMParser.<init>(Unknown Source) at org.apache.xerces.jaxp.DocumentBuilderImpl.<init>(Unknown Source) at org.apache.xerces.jaxp.DocumentBuilderFactoryImpl.newDocumentBuilder(Unknown Source) at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.createDocument(SAX2DOM.java:326) at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.<init>(SAX2DOM.java:85) at com.sun.org.apache.xalan.internal.xsltc.runtime.output.TransletOutputHandlerFactory.getSerializationHandler(TransletOutputHandlerFactory.java:187) at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.getOutputHandler(TransformerImpl.java:392) at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerHandlerImpl.setResult(TransformerHandlerImpl.java:137) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.setup(DomHelper.java:205) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.<init>(DomHelper.java:190) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.<init>(DomHelper.java:181) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.<init>(DomHelper.java:167) at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:107) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:904) ... 34 more 2011-3-18 16:31:20 org.apache.catalina.core.StandardContext filterStart 严重: Exception starting filter struts2 Unable to load configuration. - [unknown location] at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:428) at org.apache.struts2.dispatcher.FilterDispatcher.init(FilterDispatcher.java:190) at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:275) at org.apache.catalina.core.ApplicationFilterConfig.setFilterDef(ApplicationFilterConfig.java:397) at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:108) at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:3800) at org.apache.catalina.core.StandardContext.start(StandardContext.java:4450) at org.apache.catalina.core.ContainerBase.addChildInternal(ContainerBase.java:791) at org.apache.catalina.core.ContainerBase.addChild(ContainerBase.java:771) at org.apache.catalina.core.StandardHost.addChild(StandardHost.java:526) at org.apache.catalina.startup.HostConfig.deployDirectory(HostConfig.java:987) at org.apache.catalina.startup.HostConfig.deployDirectories(HostConfig.java:909) at org.apache.catalina.startup.HostConfig.deployApps(HostConfig.java:495) at org.apache.catalina.startup.HostConfig.start(HostConfig.java:1206) at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:314) at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:119) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053) at org.apache.catalina.core.StandardHost.start(StandardHost.java:722) at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1045) at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443) at org.apache.catalina.core.StandardService.start(StandardService.java:516) at org.apache.catalina.core.StandardServer.start(StandardServer.java:710) at org.apache.catalina.startup.Catalina.start(Catalina.java:583) 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:597) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413) Caused by: Unable to load configuration. - [unknown location] at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:69) at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:371) at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:415) ... 28 more Caused by: Caught exception while loading file struts-default.xml - [unknown location] at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:913) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadDocuments(XmlConfigurationProvider.java:154) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.init(XmlConfigurationProvider.java:121) at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:179) at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66) ... 30 more Caused by: java.lang.ClassCastException: org.apache.xerces.parsers.XML11Configuration cannot be cast to org.apache.xerces.xni.parser.XMLParserConfiguration at org.apache.xerces.parsers.DOMParser.<init>(Unknown Source) at org.apache.xerces.parsers.DOMParser.<init>(Unknown Source) at org.apache.xerces.jaxp.DocumentBuilderImpl.<init>(Unknown Source) at org.apache.xerces.jaxp.DocumentBuilderFactoryImpl.newDocumentBuilder(Unknown Source) at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.createDocument(SAX2DOM.java:326) at com.sun.org.apache.xalan.internal.xsltc.trax.SAX2DOM.<init>(SAX2DOM.java:85) at com.sun.org.apache.xalan.internal.xsltc.runtime.output.TransletOutputHandlerFactory.getSerializationHandler(TransletOutputHandlerFactory.java:187) at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.getOutputHandler(TransformerImpl.java:392) at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerHandlerImpl.setResult(TransformerHandlerImpl.java:137) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.setup(DomHelper.java:205) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.<init>(DomHelper.java:190) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.<init>(DomHelper.java:181) at com.opensymphony.xwork2.util.DomHelper$DOMBuilder.<init>(DomHelper.java:167) at com.opensymphony.xwork2.util.DomHelper.parse(DomHelper.java:107) at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadConfigurationFiles(XmlConfigurationProvider.java:904) ... 34 more [#SMS#] [INFO 2011-03-18 16:31:20,406] Filter initialized. Response buffering is enabled 2011-3-18 16:31:20 org.apache.catalina.core.StandardContext start 严重: Error filterStart 2011-3-18 16:31:20 org.apache.catalina.core.StandardContext start 严重: Context [/SMS2] startup failed due to previous errors 2011-3-18 16:31:20 org.apache.catalina.core.ApplicationContext log 信息: Closing Spring root WebApplicationContext