COMP 310 Spring 2010	Lec26: Remote Dynamic Class Loading with RMI,  Chat Program Use Cases

Remote Dynamic Class Loading with RMI

Today we will see if we can get everyone's RMI demo code from Lec24 to work and actually send code across the web. 

Remote dynamic class load process (all transparent to coder and user):

1. Sender serializes the object's data into a byte stream, including the object's class name and the java.rmi.server.codebase property's value in the header of the byte stream.
2. The byte stream is transmitted from the sender to the receiver.
3. The reciever reads at the object's class name in the byte stream header and looks to see if it has that class already in its local class path.
   • If the class file is located locally, then the reciever uses that class file as the template to create the reconstructed object from the rest of the serialized data.
   • Otherwise, the reciever reads thejava.rmi.server.codebase property value in the byte stream header and
     1. Does an http-style request to that class file server, having translated a fully qualified class name, e.g. aPackage.subPackage.MyClass into a directory path, e.g. aPackage/subPackage/MyClass.class.
     2. Having now obtained the proper class file, the receiver now uses it as the template to reconstruct the object from the rest of the serialized data.

RMI Chat Program

Today, we will also start working on our chat program project.    See the requirements for the chat program in HW07.

Use Cases

A use case is an example of how a user might interact with an application.    To develop an application, one of the very first things that a developer must work with the customer to collect and analyze as many use cases as possible.    It is from these use cases that a picture is built up that tells the developer how exactly the user (or any external entity) will interact with the system being built and thus how the sytem needs to be built.

A Use Case Diagram (a standard type of UML diagram) is used to visually represent a use case.   The main components of Use Case diagrams are the "actors", the users or other external entities, and the various components of the system being built.  Arrows are used to indicate interactions between components. 

In class we will develop some use cases for our chat program.

References:

• Comp310 Java Resources page on Use Cases
• Wikipedia articles on Use Cases and Use Case Diagrams.
• http://www.objectmentor.com/resources/articles/usecases.pdf
• http://www.parlezuml.com/tutorials/usecases.htm (read to PDF docs that are linked here)

© 2010 by Stephen Wong