Web Development

I have multi-layered client server application. I want to create a jar file for each layer as well as a jar file for the common classes used by the server and the client. How do I get these Jar files to interact with each other? I know how to createan executable jar and a normal jar, but how do I link the 2 together?

e.g. I have a server layer which is an executable Jar. This talks to the workflow layer which is a jar, which talks to the business rules layer (also a jar) and it talks to thedata access layer (a jar).