I had to answer the same question not too long ago but my circumstance changed and I no longer needed to run JBoss 4.2.2 w/ Java 6. However, in my search for an answer I found the following...
* RedHat's JBoss Enterprise 4.3 is basically open source JBoss 4.2.1 + bug fixes (or something close like that)
The link above describes how to get RedHat 4.3 to run with Java 6. (I found the same info in a post somewhere else for the open source version.)
With all of that said, I also ran across an official statement from JBoss stating that any configuration of JBoss not officially supported will not be troubleshooted. So for instance, if you get JBoss 4.2.2 and Java 6 to run, encounter an issue and look to the community for help, the response of JBoss posters will be to move to a configuration that is supported.
Thanks for your replies. The problem is we are using a third party rules engine - iLog JRules 6.7 and that only supports JBoss versions 4.2.2 or lower. We need to move our application to Java 6 since we need to add support for 64 bit OS. Also, we were planning on moving to Java 6 update 19 since that has the fix for the Oracle TLS renegotiation bug. So the fact that JBoss 4.2.x can be made to work with Java 6, does that mean any java update should be fine?
Another unrelated question, will having Oracle 11g cause a problem with the Java and JBoss versions?