The goal of this article is to illustrate with UML diagrams EJB programming applying J2EE design patterns. Work in Progress ...

Contents :

1. EJB Class diagrams
2. ServiceLocator
3. Links about presentations and tutorials about EJB.
4. Credits - about the author of this article and to know if you can use the diagrams in your project

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EJB Class Diagram

Note : All the names of the classes are followed by a number because the tool I use does not authorize to use the existing names of EJB classes. The final version of diagrams will be "clean".

Class Diagram of the example

Description

• InterestAction is a Struts class, an open source framework. InterestAction is Controller servlet which processes the client request and interacts with the Business logic layer
• BusinessDelegate is based on the Business Delegate Design Pattern, it encapsulates business services
• InterestVO is a Value Object, encapsulates the business data which interface the Presentation Tiers to the Business Tiers
• ServiceLocator is used to abstract all JNDI usage and to hide the complexities of initial context creation and the EJB home object lookup
• InterestHome is the Home Interface
• Interest is the Remote Interface
• InterestBean is the Stateless Session Bean

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Messages Description

• 1 The Business Delegate calls the ServiceLocator to get a reference on the Home Interface
• The Service Locator does the following actions :
  • 1.1 gets a JNDI context
  • 1.2 looks up a reference on the EJB Home Interface
  • 1.3 narrows the reference to get a remote reference to the Home Interface
• 2 The Home Interface returns a reference on the Remote Interface with create method

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Struts framework : http://jakarta.apache.org/struts

The J2EE design patterns : http://developer.java.sun.com/developer/technicalArticles/J2EE/patterns/

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4 Credits

Author

I am a French developer who lives in London (CV).

Copyrights

The diagrams are free ! However, if you want to use it for commercial purposes, please send me an e-mail.

Otherwise, you can use it if you add the following credits :

Diagrams by Jean-Michel Garnier on July 2002. Based on article by Jean-Michel Garnier in the http://rollerjm.free.fr web site.

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For any comments / suggestions : send an e-mail to g a r n i e r j m @ y a h o o.f r (remove the spaces to get my e-mail, I have done that bc the sobig virus has filled my mailbox!)