Konstantin Mosesov has added a new module to Kamailio development branch that allow embedded execution of Java compiled code. Java applications get access to attributes of current processed SIP messages and can execute internal Kamailio functions via Java Native Interface (JNI).
You can learn more about the new module from its readme documentation:
Effectively, one can write the SIP routing logic in Java and let Kamailio execute the code at runtime faster than as external application. This extension enables rapid integration of Kamailio in existing environments developed on Java technology.
The new module adds to a group of existing embedded interpreters in Kamailio, respectively: app_lua (for Lua language), app_mono (for managed languages C#/.Net, F#, …), app_perl (for Perl language) and app_python (for Python language).