我尝试在oracle linux，tomcat
7和jdk1.7上运行Web应用程序，并且在tomcat重新启动后首页加载时出现异常。仅在第一个应用程序页面加载时发生异常。应用程序是在jdk1.6上开发的，并且在服务器上安装了jdk1.4-compact和jdk1.7，但是我在tomcat/bin/setclasspath.sh文件中输入了JAVA_HOME和JRE_HOME的jdk1.7路径。有什么想法为什么我会得到这个例外？

Jan 03, 2012 5:11:28 PM org.apache.catalina.startup.Catalina start
INFO: Server startup in 10261 ms
Jan 03, 2012 5:15:49 PM org.apache.commons.digester.Digester getParser
SEVERE: Digester.getParser: 
java.lang.UnsupportedOperationException: This parser does not support specification "null" version "null"
    at javax.xml.parsers.SAXParserFactory.setSchema(SAXParserFactory.java:419)
    at org.apache.commons.digester.Digester.getFactory(Digester.java:541)
    at org.apache.commons.digester.Digester.getParser(Digester.java:791)
    at org.apache.commons.digester.Digester.getXMLReader(Digester.java:1068)
    at org.apache.commons.digester.Digester.parse(Digester.java:1916)
    at org.apache.tiles.definition.digester.DigesterDefinitionsReader.read(DigesterDefinitionsReader.java:329)
    at org.apache.tiles.definition.dao.BaseLocaleUrlDefinitionDAO.loadDefinitionsFromURL(BaseLocaleUrlDefinitionDAO.java:276)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.loadDefinitionsFromURLs(CachingLocaleUrlDefinitionDAO.java:251)
    at org.apache.tiles.definition.dao.ResolvingLocaleUrlDefinitionDAO.loadDefinitionsFromURLs(ResolvingLocaleUrlDefinitionDAO.java:65)
    at org.apache.tiles.definition.dao.ResolvingLocaleUrlDefinitionDAO.loadParentDefinitions(ResolvingLocaleUrlDefinitionDAO.java:58)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.loadDefinitionsFromURLs(CachingLocaleUrlDefinitionDAO.java:239)
    at org.apache.tiles.definition.dao.ResolvingLocaleUrlDefinitionDAO.loadDefinitionsFromURLs(ResolvingLocaleUrlDefinitionDAO.java:65)
    at org.apache.tiles.definition.dao.ResolvingLocaleUrlDefinitionDAO.loadParentDefinitions(ResolvingLocaleUrlDefinitionDAO.java:58)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.loadDefinitionsFromURLs(CachingLocaleUrlDefinitionDAO.java:239)
    at org.apache.tiles.definition.dao.ResolvingLocaleUrlDefinitionDAO.loadDefinitionsFromURLs(ResolvingLocaleUrlDefinitionDAO.java:65)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.loadDefinitions(CachingLocaleUrlDefinitionDAO.java:222)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.checkAndloadDefinitions(CachingLocaleUrlDefinitionDAO.java:204)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.getDefinitions(CachingLocaleUrlDefinitionDAO.java:154)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.getDefinition(CachingLocaleUrlDefinitionDAO.java:123)
    at org.apache.tiles.definition.dao.CachingLocaleUrlDefinitionDAO.getDefinition(CachingLocaleUrlDefinitionDAO.java:54)
    at org.apache.tiles.definition.UnresolvingLocaleDefinitionsFactory.getDefinition(UnresolvingLocaleDefinitionsFactory.java:105)
    at org.apache.tiles.impl.BasicTilesContainer.getDefinition(BasicTilesContainer.java:364)
    at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:618)
    at org.apache.tiles.impl.BasicTilesContainer.render(BasicTilesContainer.java:321)
    at org.apache.struts2.views.tiles.TilesResult.doExecute(TilesResult.java:105)
    at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)
    at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:373)
    at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:277)
    at org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:52)
    at org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:485)
    at org.apache.struts2.dispatcher.FilterDispatcher.doFilter(FilterDispatcher.java:395)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
    at org.apache.coyote.ajp.AjpProcessor.process(AjpProcessor.java:200)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722)