How do I get the pre-processor working with idltojava?
The pre-processor has to be findable by idltojava, and the right options must somehow be passed to it. Sun actually documents what’s going on here, and you can read about it in the idltojava documentation that came with the idltojava compiler for your platform. Or, see the FAQ below about using other pre-processors. Most of the details are re-stated there.