ContentsApplication DesignCollaboration

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Just as delegation has a functional side and an operational side, so does collaboration.

Collaboration involves timing, sequences of events, and the possibility of concurrence. As long as your servlet doesn't update any external resources, these issues are usually taken care of by the infrastructure. Because HTTP is stateless, your user doesn't have any risk of running into a transactional deadlock.

Although this topic is outside of the scope of this tutorial, here are a few of things to keep in mind:

• your servlet may be running sequentially in a single thread or in multiple threads - it is not safe to assume that you can store something in an instance variable and reference it later (with exception to the init() method)
• session objects are your friend - use them a lot
• use connection pooling for JDBC or else use EJB - don't write the code if you don't have to
• cache as much information as you can to avoid load on the servlet engine, web server, and the browser... they are wait for your servlet to complete it's doGet() or doPost() method and could cause a tie-up on a busy server

There is another perspective on collaboration, too... organizational. Unless you are doubling as the web page designer, the HtmlPage class is an ugly and inefficient way to make web pages. Yeah, they work - which is OK for a prototype - but you really should think about using a WYSIWYG HTML editor and separating your servlet from the web page design. I'll talk more about this issue and give my recommendation in an upcoming section.

ContentsApplication DesignCollaboration

Previous: Interfaces | Next: Leaks