JSTL TransformerFactoryImpl ClassCastException on WAS 6.0.2.11

Keywords:
JSTL TransformerFactoryImpl ClassCastException WAS 6.0.2.11 xalan JAXP core xerces

Problem:
A web application that has the following properties:

1. includes the JAXP api jar files (in WEB-INF\lib)
2. deploys with the class loader properties of "Parent Last"
3. uses JSTL core

Will encounter the following stack trace from WAS when ever a JSP is loaded that contains JSTL (core reference):

JSP Processing Error
HTTP Error Code: 500
java.lang.ClassCastException: org.apache.xalan.processor.TransformerFactoryImpl
at javax.xml.transform.TransformerFactory.newInstance(Unknown Source)
at com.ibm.ws.jsp.translator.visitor.validator.PageDataImpl._getInputStream(PageDataImpl.java:125)
at com.ibm.ws.jsp.translator.visitor.validator.PageDataImpl.getInputStream(PageDataImpl.java:117)
at org.apache.taglibs.standard.tlv.JstlBaseTLV.validate(JstlBaseTLV.java:156)
at org.apache.taglibs.standard.tlv.JstlCoreTLV.validate(JstlCoreTLV.java:96)
at com.ibm.ws.jsp.translator.visitor.validator.ValidateVisitor.validateTagLib(ValidateVisitor.java:939)
at com.ibm.ws.jsp.translator.visitor.validator.ValidateVisitor.visitJspRootStart(ValidateVisitor.java:453)
at com.ibm.ws.jsp.translator.visitor.JspVisitor.processJspElement(JspVisitor.java:124)
at com.ibm.ws.jsp.translator.visitor.JspVisitor.visit(JspVisitor.java:110)
at com.ibm.ws.jsp.translator.JspTranslator.processVisitors(JspTranslator.java:121)
at com.ibm.ws.jsp.translator.utils.JspTranslatorUtil.translateJsp(JspTranslatorUtil.java:168)
at com.ibm.ws.jsp.translator.utils.JspTranslatorUtil.translateJspAndCompile(JspTranslatorUtil.java:81)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper.translateJsp(JSPExtensionServletWrapper.java:360)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper._checkForTranslation(JSPExtensionServletWrapper.java:329)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper.checkForTranslation(JSPExtensionServletWrapper.java:237)
at com.ibm.ws.jsp.webcontainerext.JSPExtensionServletWrapper.handleRequest(JSPExtensionServletWrapper.java:144)
at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3003)
at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:221)
at com.ibm.ws.webcontainer.VirtualHost.handleRequest(VirtualHost.java:210)
at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:1958)
at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:88)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:472)
at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:411)
at com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:101)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.requestComplete(WorkQueueManager.java:566)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.attemptIO(WorkQueueManager.java:619)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager.workerRun(WorkQueueManager.java:952)
at com.ibm.ws.tcp.channel.impl.WorkQueueManager$Worker.run(WorkQueueManager.java:1039)
at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1470)

Solution:
In short, make sure the JSPs, JSTL refs and the web app are 2.4 compliant (see past post: What Spec?) and install the latest fix pack for WAS from IBM.

In detail, the following Problem ID is a different issue but underlying problem is the same - incorrect handling of loading XML & XSLT API classes for Parent Last apps - IBM - PK26233. The comment says it is resolved in the fix pack 6.0.2.15 for WebSphere Application Server, but I used 6.0.2.17 seeing it was newer - V6.0.2 Fix Pack 17.