Today I have found interesting articles about java framework developing.

The first link is an implementation of opensource java plugin framework:

http://jpf.sourceforge.net/about.html

The next one article is an example of develop java plug-in from scratch. Form me this link is the best way to use a plug-in architecture in your application

http://twit88.com/blog/2007/10/07/develop-a-java-plugin-framework/

The last article explain how to read a xml configuration file in easy way:

http://twit88.com/blog/2007/09/18/xml-configuration-for-java-program/