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Go away - we're closed

Posted by daniel on May 14, 2004 at 6:01 AM PDT

When you redeploy your J2EE apps, how do you handle active users?

In today's Weblogs, Srikanth Shenoy makes an analogy to entering a store with a welcoming sign that says "OPEN". You are then suddenly ejected from the store without explanation and now look at the sign and it reads "CLOSED". Shenoy calls this the Retail Outlet Pattern and suggests how to avoid this in your J2EE application.

He writes that what you would want is a more gentle treatment as a shopper in a real store. "You'd expect that the outlet lets you shop now that you have entered it before the "CLOSED" sign is put up. right?

Guess what - a lot of J2EE systems in production might not be doing that at all. When new deployments go out, active users on the system are unceremoniously ousted." He suggests a solution that he has not implemented and asks for your feedback and experience reports.

John Reynolds takes A second look at BPELJ. Initially, he said, " Intermingling Java snippets with XML invoked a gag reflex, and it was hard for me to keep reading." But on second look he writes that "I have a philosphical problem with including Java snippets in BPELJ, but I understand the intent.

The justification for Java snippets is the plan to use BPELJ as the notation for JSR-207 Java class annotations. Annotations will be used to define BPELJ fragments for specific classes (much like XDoclet tags for EJBs). With the proper BPELJ annotation, any POJO class can be transformed into a process step... No need for a Session Bean wrapper, just annotate the POJO and it can be deployed into a BPELJ "container" (much like EJBs and their containers). I have to admit that the concept is pretty cool."


In
Also in Java Today
, although you may want to persist information in XML files, as a Java developer you want to interact with this information as objects. Satya Komatineni explains Java Architecture for XML Binding in The State of JAXB: Availability, Suitability, Analysis, and Architecture. Komatineni writes "JAXB makes use of XML schema definitions for generating the bindings between XML and Java. This current dependency on XML schemas is somewhat debated, but in situations where the schemas are readily available, JAXB works quite well in generating the Java classes."

What happens when your development tools become pluggable frameworks? The NetBeans and Eclipse communities are exploring this now. Extensible Programming for the 21st Century is an updated and revised version of Gregory Wilson's March 2003 Dr. Dobbs article "XML-Based Programming Systems" in which he predicts " that next-generation programming systems will store source code as XML, rather than as flat text. Programmers will not see or edit XML tags; instead, their editors will render these models to create human-friendly views, just as web browsers render HTML." The bulk of the article is devoted to listing and responding to objections raised by tools as pluggable frameworks and code as XML.


How useful are comments?
In today's Forums,
jwenting asks about the Utility of Comments, writing "Do you really think their comments would be of higher readability than their code?" Follow the thread up to see what he is commenting on.

It's not just the quantum world where measurement has impact on what is being measured. In Mis-measurement, bookclub moderator John Mitchell writes "Brooks story of the programmers gaming the project rules on program space usage reminds me that what gets measured is what gets the attention. Has there been any improvement in management's ability to focus on what really matters rather than what can be easily measured in the last 30 years?"


In today's Projects and Communities , researchers at The Applied Software Systems Laboratory (TASSL) at Rutgers University are using JXTA technology as part of their study on the implications of P2P overlay networks in highly dynamic systems.

The Appfuse project is an application designed to ease Java Tomcat/MySQL webapp development. "Features include CMA, Remember Me, Self Registration, Password Hint. The fuse to start your apps."


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