OC4J Rmi Client: NoClassDefFoundError: javax/ejb/EJBHome

Trying to run an OC4J rmi client where the oc4jclient.jar was packaged with the project (no longer in the jdeveloper home directory) produced some vexing problems with the following error:

java.lang.NoClassDefFoundError: javax/ejb/EJBHome
at java.lang.Class.getDeclaredMethods0(Native Method)
...

despite having the ejb.jar file on the classpath. After much frustration, it turns out that oc4jclient.jar uses a Class-Path attribute in its manifest:

Class-Path: lib/ejb.jar lib/mail.jar lib/oc4j_orb.jar lib/orbbase.jar
lib/iiop_support.jar lib/jms.jar lib/jta.jar ../../lib/xmlparserv2.ja
r ../../opmn/lib/optic.jar ../../oracle/jlib/oraclepki.jar ../../jlib
/oraclepki.jar ../../oracle/jlib/ojpse.jar ../../jlib/ojpse.jar

The problem seems to be that although the application classloader does have ejb.jar on the classpath, the oc4jclient.jar gets loaded with a different classloader that can't see it, and expects the ejb.jar to be in a lib dir relative to itself. Turns out you can ignore all the other jar references, only ejb.jar is required (luckily). So, where ever you place the oc4jclient.jar, just create a lib dir in the same directory and drop the ejb.jar into it--then the problem should be solved.

Another bit of weirdness was that it wouldn't seem to work with jdk 1.5.0_06. We looked in the ext dir for anything that might be messing it up but didn't find anything obvious. It seems too bizarre to the the jdk version was also causing a problem, but simply switching to 1.5.0_02 would fix other classpath problems.