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Class Loading Issues

It is possible that the Java libraries you have specified in the plugin libraries list conflict with the ones already loaded by Oxygen XML Author. To instruct the plugin to prefer its libraries over the ones used by Oxygen XML Author, you can add the following attribute on the <plugin> root element: classLoaderType="preferReferencedResources" from the plugin.xml descriptor file.

A Late Delegation Class Loader (the main class loader in Oxygen XML Author) is a java.net.URLClassLoader extension that prefers to search classes in its own libraries list and only if a class is not found there to delegate to the parent class loader.

The main Oxygen XML Author Class Loader uses as libraries all JARS specified in the [OXYGEN_INSTALL_DIR]\lib directory. Its parent class loader is the default JVM Class loader. For each plugin instance, a separate class loader is created having as parent the Oxygen XML Author Class Loader.

The plugin class loader can be either a standard java.net.URLClassLoader or a LateDelegationClassLoader (depending on the attribute classLoaderType in the plugin.xml). Its parent class loader is always the Oxygen XML Author LateDelegationClassLoader.

If you experience additional problems, such as:

java.lang.LinkageError: ClassCastException: 
attempting to cast 
jar:file:/C:/jdk1.6.0_06/jre/lib/rt.jar!/
javax/xml/ws/spi/Provider.class
tojar:file:/D:/Program
 Files/Oxygen XML Editor
 12/plugins/wspcaccess/../../xdocs/lib/jaxws/
jaxws-api.jar!/javax/xml/ws/spi/Provider.class
 at javax.xml.ws.spi.Provider.provider(
Provider.java:94) at
 javax.xml.ws.Service.<init>(Service.java:56)
.............................................

The cause could be the fact that some classes are instantiated using the context class loader of the current thread. The most straightforward fix is to write your code in a try/finally statement:

ClassLoader oldClassLoader = 
    Thread.currentThread().getContextClassLoader();
try {
  //This is the implementation of the 
  //WorkspaceAccessPluginExtension plugin interface.
  Thread.currentThread().setContextClassLoader(
    CustomWorkspaceAccessPluginExtension.
      this.getClass().getClassLoader());
  //WRITE YOUR CODE HERE
} finally {
  Thread.currentThread().
   setContextClassLoader(oldClassLoader);
}