Saturday, November 12, 2011

J2EE Design Patterns

Recent times I have tried to look into the J2EE design patterns, as I am gaining the experience in Java development it is necessary the I should have complete Idea on the J2EE design patterns. Here I am planning to share my understanding, key points that I believe most important for normal java developer.

Most of J2EE/JEE based applications has the Presentation layer (which is visible to the user), Business Layer (which has the business components implementation) and Integration Layer (which integrates with other systems or databases). So, the people have classified the J2EE design patterns in to three types as below:

Presentation tier Patterns:

Business Tier Patterns:
  • Business Delegate
  • Service Locator
  • Session Fa├žade
  • Value List Handler
  • Business Object
  • Composite Entity

Integration tier patterns:
  • Data Access Object
  • Service Activator
  • Web Service Broker
  • Domain Service


I have listed the most of the design patterns above which I feel more important. Most of the design patters depends on one or more, so implementation of a complete J2EE based and good architecture enterprise application requires all the design patters listed above.

Design pattern definition: A design pattern describes a proven solution, from experienced hands, for a recurring design problem. These solutions are very generic. They are described in well-defined Pattern Templates, with the most popular template defined by the Gang of four. For a recurring problem there would be a single solution in a single context ie. There would be none other than one solution for single problem in a single context.

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