Java Plugin Framework: plug-in infrastructure library for Java projects

 JPF provides a runtime engine that dynamically discovers and loads
 "plug-ins". A plug-in is a structured component that describes itself to JPF
 using a "manifest". JPF maintains a registry of available plug-ins and the
 functions they provide (via extension points and extensions).
 .
 One major goal of JPF is that the application (and its end-user) should not
 pay any memory or performance penalty for plug-ins that are installed, but
 not used. Plug-ins are added to the registry at application start-up or
 while the application is running but they are not loaded until they are
 called.