I am deploying a J2EE web application in Websphere Application Server 8.5.
The web application has a shared library with all the third party libraries. All the internally coded libraries are inside the WEB-INF/lib folder.
The problem is that in only some jsps WAS it is throwing the following exception.
I think it is related with xercesImpl-2.8.1.jar but I don't understand why it is throwing this exception and why it is throwing in only some pages.
In tomcat it is working perfectly.
java.lang.ClassCastException: org.apache.xerces.jaxp.SAXParserFactoryImpl incompatible with javax.xml.parsers.SAXParserFactory
at javax.xml.parsers.SAXParserFactory.newInstance(Unknown Source)
at org.apache.taglibs.standard.tlv.JstlBaseTLV.validate(JstlBaseTLV.java:152)
at org.apache.taglibs.standard.tlv.JstlCoreTLV.validate(JstlCoreTLV.java:96)
at com.ibm.ws.jsp.translator.visitor.validator.ValidateVisitor.validateTagLib(ValidateVisitor.java:1129)
at com.ibm.ws.jsp.translator.visitor.validator.ValidateVisitor.visitJspRootStart(ValidateVisitor.java:491)
at com.ibm.ws.jsp.translator.visitor.JspVisitor.processJspElement(JspVisitor.java:233)
at com.ibm.ws.jsp.translator.visitor.JspVisitor.visit(JspVisitor.java:216)
at com.ibm.ws.jsp.translator.JspTranslator.processVisitors(JspTranslator.java:127)
at com.ibm.ws.jsp.translator.utils.JspTranslatorUtil.translateJsp(JspTranslatorUtil.java:254)
at com.ibm.ws.jsp.translator.utils.JspTranslatorUtil.translateJspAndCompile(JspTranslatorUtil.java:121)
at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper.translateJsp(AbstractJSPExtensionServletWrapper.java:535)
at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper._checkForTranslation(AbstractJSPExtensionServletWrapper.java:452)
at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper.checkForTranslation(AbstractJSPExtensionServletWrapper.java:283)
at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionProcessor.findWrapper(AbstractJSPExtensionProcessor.java:456)
at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionProcessor.getServletWrapper(AbstractJSPExtensionProcessor.java:337)
at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:963)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.dispatch(WebAppRequestDispatcher.java:1384)
at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.forward(WebAppRequestDispatcher.java:193)
at com.ieci.tecdoc.isicres.servlets.QryInitAdvanSearch.doWork(QryInitAdvanSearch.java:209)
at com.ieci.tecdoc.isicres.servlets.QryInitAdvanSearch.doGet(QryInitAdvanSearch.java:67)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:575)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:668)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1214)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:774)
at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:456)
at com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:178)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.invokeTarget(WebAppFilterChain.java:125)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:92)
at com.ieci.tecdoc.isicres.filters.URLCheckFilter.doFilter(URLCheckFilter.java:106)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:192)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:89)
at com.ieci.tecdoc.isicres.filters.LoginCheckFilter.doFilter(LoginCheckFilter.java:119)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:192)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:89)
at com.ieci.tecdoc.isicres.filters.XSSFilter.doFilter(XSSFilter.java:72)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:192)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:89)
at com.ieci.tecdoc.isicres.filters.UTF8Filter.doFilter(UTF8Filter.java:65)
at com.ibm.ws.webcontainer.filter.FilterInstanceWrapper.doFilter(FilterInstanceWrapper.java:192)
at com.ibm.ws.webcontainer.filter.WebAppFilterChain.doFilter(WebAppFilterChain.java:89)
at com.ibm.ws.webcontainer.filter.WebAppFilterManager.doFilter(WebAppFilterManager.java:926)
at com.ibm.ws.webcontainer.filter.WebAppFilterManager.invokeFilters(WebAppFilterManager.java:1023)
at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3703)
at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:304)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:962)
at com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1662)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:195)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:458)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:522)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:311)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:87)
at com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
at com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
at com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
at com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
Basically, there is no need to package libraries that implement standardized APIs (like javax.xml) as most of them are already provided either by JRE or application server. This allows for avoiding various incompatibility issues like the one that you face.
If you still need to use a specific version of Xerces, change classloading policy of the web module to PARENT_LAST. In this case the library will be picked up from WEB-INF/lib. This does not guarantee you won't have problems though.
To sum it up: remove xercesImpl-2.8.1.jar from the application. Your operating environment provides XML parser implementation. In most cases you don't need to know which one.
I solved it changing the association of the shared libraries.
Originally the xerces libraries were included as a shared library under application level, so these libraries were loaded before than the application server.
I changed the shared library association to module level, now these libraries are loaded after than the application server and the exception dissappeared.
来源：https://stackoverflow.com/questions/19585014/was-8-5-java-lang-classcastexception-org-apache-xerces-jaxp-saxparserfactoryim