We are aware of JQF and the jUnit integration is the best part there. We opted to taking the "Fuzzed Data Provider" approach to be more compatible to the approach in C/C++, Go and Python...
How do you deal with structured formats, like XML?
In JQF you would just write a XML generator (see their examples). If you just use the "sequence of bytes" approach as AFL does, then a lot of your inputs might be immediately rejected by the parser.
We use our internal grammar generator similar to libprotobuf mutator. For the OSS solution, we recommend to use libprotobuf mutator though. The reason to abstract this is that we don't want to write the grammars for a single programming language only.