How to merge/crosslink Javadoc?

If you have the standard Javadoc for a few different projects, how can you process them to create a single unified set of documentation in which everything is cross-linked? Ideally, the result would be similar to the documentation for the various modules i开发者_开发技巧n the NetBeans Platform:

http://bits.netbeans.org/dev/javadoc/index.html

but I've looked at their build scripts and they're predicated on you building everything from source. I'm looking for something which could also handle linking in Javadoc for third-party libraries, so I'd imagine it would need to be a post-processing operation.

I can't be the first person to ever want this. Any ideas?

Try using the '-linkoffline' or '-link' options described here http://java.sun.com/j2se/1.3/docs/tooldocs/solaris/javadoc.html#linkoffline