This is a Burp Extension for beautifying JSON output. There exists a python version in the BApp Store at the moment. After some difficulties with Jython I opted to port it to Java.
Download the repo > Open Burp > Extender > Extensions > Add > Java > ~/burp/out/artifacts/burp_jar/burp
All development was done in IntelliJ.
In case any changes need to be made make sure to include ~/lib/gson-2.8.0 in File > Project Structure > Libraries > Plus.
Once gson is added do the following to create the new jar archive.
File > Project Structure > Artifacts > Plus Sign > Jar > From modules with dependencies > OK and check the Include in project build checkbox. After this anytime the project builds a .jar archive will be made. Thanks Gruber for those instructions.