Question

i need to modify an xml document which has multiple namespaces. my code runs without problems on my local machine but i’m encountering java.lang.IncompatibleClassChangeError when i deployed it to IBM Websphere application server.

i’m using xercesImpl-2.8.1.jar and xalan-2.7.0.jar.
what is causing this error and how do i resolve it? alternatively, are there other ways to modify xml documents with namespace support?

Code:

System.setProperty("javax.xml.parsers.DocumentBuilderFactory", "org.apache.xerces.jaxp.DocumentBuilderFactoryImpl");

DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
dbf.setNamespaceAware(true);
DocumentBuilder db = dbf.newDocumentBuilder();
org.w3c.dom.Document doc = db.parse(new java.io.FileInputStream("c:/test.xml"));

System.setProperty("javax.xml.xpath.XPathFactory", "org.apache.xpath.jaxp.XPathFactoryImpl");
XPathFactory xf = XPathFactory.newInstance();
XPath xpath = xf.newXPath();
xpath.setNamespaceContext(new MyNamespaceContext());

// get the node for editing
String xpathExpr = ...
org.w3c.dom.Node n = (org.w3c.dom.Node)xpath.compile(xpathExpr).evaluate(doc, XPathConstants.NODE); // IncompatibleClassChangeError here

exception stack trace:

java.lang.IncompatibleClassChangeError
        at org.apache.xpath.jaxp.JAXPPrefixResolver.getNamespaceForPrefix(JAXPPrefixResolver.java:45)
        at org.apache.xpath.compiler.Lexer.mapNSTokens(Lexer.java:587)
        at org.apache.xpath.compiler.Lexer.tokenize(Lexer.java:265)
        at org.apache.xpath.compiler.Lexer.tokenize(Lexer.java:96)
        at org.apache.xpath.compiler.XPathParser.initXPath(XPathParser.java:110)
        at org.apache.xpath.XPath.<init>(XPath.java:176)
        at org.apache.xpath.XPath.<init>(XPath.java:264)
        at org.apache.xpath.jaxp.XPathImpl.compile(XPathImpl.java:394)
        at com.ibm._jsp._xml._jspService(_xml.java:94)
        at com.ibm.ws.jsp.runtime.HttpJspBase.service(HttpJspBase.java:87)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
        at com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1146)
        at com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:592)
        at com.ibm.ws.wswebcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:525)
        at com.ibm.wsspi.webcontainer.servlet.GenericServletWrapper.handleRequest(GenericServletWrapper.java:122)
        at com.ibm.ws.jsp.webcontainerext.AbstractJSPExtensionServletWrapper.handleRequest(AbstractJSPExtensionServletWrapper.java:232)
        at com.ibm.ws.webcontainer.webapp.WebApp.handleRequest(WebApp.java:3548)
        at com.ibm.ws.webcontainer.webapp.WebGroup.handleRequest(WebGroup.java:269)
        at com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:831)
        at com.ibm.ws.wswebcontainer.WebContainer.handleRequest(WebContainer.java:1478)
        at com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:133)
        at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:458)
        at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewInformation(HttpInboundLink.java:387)
        at com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.ready(HttpInboundLink.java:267)
        at com.ibm.ws.ssl.channel.impl.SSLConnectionLink.determineNextChannel(SSLConnectionLink.java:1037)
        at com.ibm.ws.ssl.channel.impl.SSLConnectionLink$MyReadCompletedCallback.complete(SSLConnectionLink.java:644)
        at com.ibm.ws.ssl.channel.impl.SSLReadServiceContext$SSLReadCompletedCallback.complete(SSLReadServiceContext.java:1818)
        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:136)
        at com.ibm.io.async.ResultHandler.complete(ResultHandler.java:196)
        at com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:751)
        at com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:881)
        at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1497)

Answer 1

i’ve managed to solve this. it was due to a class file (javax.xml.namespace.NamespaceContext) being loaded from the xml-apis.jar which i was also using.

javax.xml.namespace.NamespaceContext is an interface present in xml-apis.jar and JRE. in the JRE’s version of the class, the interface methods are all marked ‘abstract’ but in the xml-apis.jar’s version, the interface methods are not abstract. i believe this caused a binary compatibility issue resulting in the error that i encountered.

so resolve my problem, i changed my classloader configuration to use the parent classloader before the application classloader so that the javax.xml.namespace.NamespaceContext from the JRE is used.