J2EE Design Patterns

Presentation Tier Antipatterns

The Model-View-Controller pattern, covered in Chapter 3, is the fundamental organizing principle for the presentation tier. The building blocks of the MVC pattern create an overall map of the application, making it easier to understand and extend. Preserving the separation of model, view, and controller is essential to maintaining these advantages.

It should be no surprise, then, that the presentation tier antipatterns have to do with the breakdown of model-view-controller separation. While these antipatterns are specific to the presentation tier, be aware that other antipatterns, such as Leak Collection and Excessive Layering, can affect the presentation tier as well.

The Magic Servlet

When servlets were first introduced, developers immediately saw the potential of combining the robust Java environment with an efficient mechanism for serving dynamic content. Server-side Java’s killer app was JDBC, a powerful and high-level mechanism for communicating with databases. Over time, technologies like JNDI and JMS were added, allowing J2EE to talk easily and directly to a large number of enterprise information systems.

Because it was suddenly so easy to talk to databases, directory servers, and messaging systems, many developers were tricked into thinking that their applications would be simple, too. Who needed a complicated design when reading a row from a database was a one-line operation? Unfortunately, as applications grew in scope, complexity crept back ...