Full explanation of the problem:

• when the node sends a class loading request for the jdbc connection wrapper class (weblogic/jdbc/rmi/internal/..._oracle_jdbc_driver_LogicalConnection_RemoteInterface.class), the JPPF code looks it up using the Weblogic class loader for the JCA connector (a weblogic.utils.classloaders.ChangeAwareClassLoader), using the getResource() method, which returns a single URL pointing to the class file.
• for this connection class, getResource() actually returns "file:/<WL_HOME>/modules/com.bea.core.utils.wrapper_1.4.0.0.jar". So this is what was returned to the node. It also explains both the ClassFormatError and the "Incompatible magic value 1347093252" message, since 1347093252 is the 4-bytes signature of a zip (or jar) file.
• however, when using the getResources() method to lookup the same class, this returns an empty Enumeration of URLs, which is the expected behavior. This will cause the node class loader to throw a ClassNotFoundException, which is caught by the Weblogic code in wlfullclient.jar, and then the Weblogic code will actually generate this class.

The fix is to use cl.getResources() instead of cl.getResource() in org.jppf.classloader.ResourceProvider.getResource(String resName, ClassLoader classLoader).