I've gotten LinkageErrors and VerifyErrors while using Xerces 1.4.1 inside jEdit
3.2pre3 with jdk 1.3.1 on linux. jEdit uses its own class loader. The rules for
class equivalence inside jvms require that a class be identical and come from
the same class loader. I fixed the problem by repackaging the xerces.jar archive
without the org/xml/ and javax/ directories.

Other people could have this problem when code they've written uses its own
class loader to load xerces. They may see it more, now that jdk1.4 is supplying
jaxp code.

My repackaged xerces.jar removed:

org/xml/
org/xml/sax/
org/xml/sax/AttributeList.class
org/xml/sax/Attributes.class
org/xml/sax/ContentHandler.class
org/xml/sax/DTDHandler.class
org/xml/sax/DocumentHandler.class
org/xml/sax/EntityResolver.class
org/xml/sax/ErrorHandler.class
org/xml/sax/HandlerBase.class
org/xml/sax/InputSource.class
org/xml/sax/Locator.class
org/xml/sax/Parser.class
org/xml/sax/SAXException.class
org/xml/sax/SAXNotRecognizedException.class
org/xml/sax/SAXNotSupportedException.class
org/xml/sax/SAXParseException.class
org/xml/sax/XMLFilter.class
org/xml/sax/XMLReader.class
org/xml/sax/helpers/
org/xml/sax/helpers/AttributeListImpl.class
org/xml/sax/helpers/AttributesImpl.class
org/xml/sax/helpers/DefaultHandler.class
org/xml/sax/helpers/LocatorImpl.class
org/xml/sax/helpers/NamespaceSupport$Context.class
org/xml/sax/helpers/NamespaceSupport.class
org/xml/sax/helpers/ParserAdapter$AttributeListAdapter.class
org/xml/sax/helpers/ParserAdapter.class
org/xml/sax/helpers/ParserFactory.class
org/xml/sax/helpers/XMLFilterImpl.class
org/xml/sax/helpers/XMLReaderAdapter$AttributesAdapter.class
org/xml/sax/helpers/XMLReaderAdapter.class
org/xml/sax/helpers/XMLReaderFactory.class
org/xml/sax/ext/
org/xml/sax/ext/DeclHandler.class
org/xml/sax/ext/LexicalHandler.class
javax/
javax/xml/
javax/xml/parsers/
javax/xml/parsers/DocumentBuilder.class
javax/xml/parsers/DocumentBuilderFactory.class
javax/xml/parsers/FactoryConfigurationError.class
javax/xml/parsers/ParserConfigurationException.class
javax/xml/parsers/SAXParser.class
javax/xml/parsers/SAXParserFactory.class


One way to solve it would be to have the xerces kit include two separate .jar
files, one with the code included in jdk1.4 and one with the xerces-specific
code. I don't know that this approach is the best way, though. 

Thanks,

Dave
dfw1@cornell.edu