java - ClassCastException: org.apache.xerces.parsers.XIncludeAwareParserConfiguration cannot be cast to org.apache.xerces.xni.parser.XMLParserConfiguration

Question

I am developing a GWT application in Eclipse and use jdom2 to read some custom xml property files.

Following a recent update my application now fails with the above error when trying to read the xml file. The relevant stack trace is:

org.apache.xerces.parsers.XIncludeAwareParserConfiguration cannot be cast to org.apache.xerces.xni.parser.XMLParserConfiguration
org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
org.apache.xerces.parsers.SAXParser.<init>(Unknown Source)
org.apache.xerces.jaxp.SAXParserImpl$JAXPSAXParser.<init>(Unknown Source)
org.apache.xerces.jaxp.SAXParserImpl.<init>(Unknown Source)
org.apache.xerces.jaxp.SAXParserFactoryImpl.newSAXParser(Unknown Source)
org.jdom2.input.sax.XMLReaders.createXMLReader(XMLReaders.java:165)
org.jdom2.input.SAXBuilder.createParser(SAXBuilder.java:871)
org.jdom2.input.SAXBuilder.buildEngine(SAXBuilder.java:854)
org.jdom2.input.SAXBuilder.getEngine(SAXBuilder.java:904)
org.jdom2.input.SAXBuilder.build(SAXBuilder.java:1116)
uk.co.platosys.db.jdbc.DatabaseProperties.loadProperties(DatabaseProperties.java:78)

Researching this problem suggests that the error can arise when incompatible versions of the xerces jars exist on the classpath.

gwt-dev-2.6.1.jar contains the xerces packages and my hunch is that this latest version of gwt-dev has bundled a version that is incompatible. However jdom2.0.5, the current release, is released with the 2.11 version of Xerces which seems to be the latest released by Apache. Putting these jars on my classpath doesn't seem to resolve matters; I have previously been able to rely on the versions in gwt-dev.

I am rather at my wits' end about this and considerably out of my comfort zone.

Answer 1

I had a same exception when I upgraded my project from GWT 2.7 to GWT 2.8. I have no idea why I had not this problem with GWT 2.7 (maybe different position of in .classpath file of Eclipse project could affect it).

The reason for that exception was that before with such code like:

DocumentBuilderFactory newInstance = DocumentBuilderFactory.newInstance();
DocumentBuilder newDocumentBuilder = newInstance.newDocumentBuilder();
baseLayoutXmlDocument = newDocumentBuilder.parse( baseLayoutSvgInputStream );

SAXParserFactory spf = SAXParserFactory.newInstance();
SAXParser sp = spf.newSAXParser();

the implementations from JDK package com.sun.org.apache.xerces.internal.jaxp was used, but after upgrade to GWT2.8 my app chose the xerces from gwt-dev.jar. I found the fix for that according to Javadoc and link here to used system properties

-Djavax.xml.parsers.DocumentBuilderFactory=com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderFactoryImpl
-Djavax.xml.parsers.SAXParserFactory=com.sun.org.apache.xerces.internal.jaxp.SAXParserFactoryImpl