I'm trying to build a Java code search engine. Apart from just searching for keywords, I would also like cross-referencing between classes to work. It should work the way eclipse's referencing works - click on anything to open the definition. Bonus would be if something like search-all-usages-of-foo works. I'm thinking of using Apache Solr to index the files and build the basic search. But I'm not sure how I'd do the crossreferencing part since Solr doesn't understand Java code. Any suggestions on what I could use here? EDIT: I mainly want to index a lot of java git repositories.