Java APIs provide a way for a JVM application to access and manage VPP.
JVpp is a VPP module providing Java APIs for VPP.
Documentation for JVpp can be found within the code. Codebase is located under vpp in folder: /vpp-api/java/jvpp/
JVpp is publicly accessible in fd.io's nexus.
The best samples can be found in Honeycomb's codebase. Since Honeycomb relies heavily on JVpp to access VPP.
Honeycomb's module using JVpp to manage VPP: https://gerrit.fd.io/r/gitweb?p=honeycomb.git;a=tree;f=v3po/v3po2vpp;hb=HEAD
VPP plugins are currently not supported. JVpp redesign is in progress, see: jVPP plugin support