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Wizard API updated!
Tim Boudreau has released a new version of the Swing Wizard library (version 0.997) that fixes the WizardException bug reported in JavaWorld's recent Open Source Java Project profile. The article's examples have been reworked to test out the new, improved WizardException. Thanks, Tim, for this helpful fix!
Open Source Java Projects: The Wizard API
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Repair invalid cached services in the Service Locator pattern
The Verified Service Locator pattern ensures cached services' validity
The Service Locator pattern locates J2EE (Java 2 Platform, Enterprise Edition) services for clients and thus abstracts the
complexity of network operation and J2EE service lookup as EJB (Enterprise JavaBean) Home and JMS (Java Message Service) component factories. The Service Locator hides the lookup process's implementation details
and complexity from clients. To improve application performance, Service Locator caches service objects to eliminate unnecessary
JNDI (Java Naming and Directory Interface) activity that occurs in a lookup operation.
When you opt to use the Service Locator pattern in J2EE development, you expect no side effects. However, cached services can be invalid, generating unexpected errors in your application. To avoid these errors, enhance the Service Locator pattern to neutralize potential problems with cached services. In this article, I present a way to empower the Service Locator pattern with a verification mechanism that recognizes and eliminates invalid cached services.
- Download the source code that accompanies this article
http://www.javaworld.com/javaworld/jw-07-2002/service/jw-0703-service.zip - Sun has provided a Web resource for J2EE design patterns (Sun Microsystems, 2002)
http://java.sun.com/blueprints/patterns/j2ee_patterns/index.html - Mastering Enterprise JavaBeans (Second Edition), Ed Roman, Scott W. Ambler, Tyler Jewell, and Floyd Marinescu (John Wiley & Sons, 2001; ISBN0471417114)
http://www.amazon.com/exec/obidos/ASIN/0471417114/javaworld - Design Patterns, Eric Gamma, Richard Helm, Ralph Johnson, and John Vlissides (Addison-Wesley, 1995; ISBN0201633612)
http://www.amazon.com/exec/obidos/ASIN/0201633612/javaworld - The Unified Modeling Language User Guide, Grady Booch, Ivar Jacobson, James Rumbaugh (Addison-Wesley, 1998; ISBN0201571684)
http://www.amazon.com/exec/obidos/ASIN/0201571684/amazon - Walter Hurst talks about the benefits of J2EE design patterns in "Design Patterns Make for Better J2EE Apps" (JavaWorld, June 2002)
http://www.javaworld.com/javaworld/jw-06-2002/jw-0607-j2eepattern.html - For more articles on design patterns, browse these JavaWorld resources:
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- Search the Design Patterns section of our Topical Index
http://www.javaworld.com/channel_content/jw-patterns-index.shtml - Read David Geary's Java Design Patterns column
http://www.javaworld.com/columns/jw-java-design-patterns-index.shtml
- Search the Design Patterns section of our Topical Index
- For more articles that address design, browse the Object-Oriented Design and Programming section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-oop-index.shtml - Browse the Java 2 Platform, Enterprise Edition (J2EE) section of JavaWorld's Topical Index
http://www.javaworld.com/channel_content/jw-j2ee-index.shtml - Talk about design patterns in our Programming Theory & Practice discussion
http://forums.idg.net/webx?50@@.ee6b806 - Sign up for JavaWorld's free weekly Enterprise Java email newsletter
http://www.javaworld.com/jw-subscribe - You'll find a wealth of IT-related articles from our sister publications at IDG.net
Free Download - 5 Minute Product Review. When slow equals Off: Manage the complexity of Web applications - Symphoniq
Free Download - 5 Minute Product Review. Realize the benefits of real user monitoring in less than an hour. - Symphoniq