Re: Maintaining Session in Application Server

Here's what Brett has to say on the subject (briefly):

"...While stateful beans can be helpful for processes or tasks that span
multiple requests, they are often slower and obviously require more memory
in the virtual machine.  Stateless session beans, though, are very fast, and
often only a few instances are needed to serve hundreds of requests.  These
qualities make them ideal for most business tasks, and preferable for better
application performance.

"...First, unless there is a reason not (emphasis in original) to use
stateless session beans, you should use them.  Using stateless beans over
stateful ones in the general case can drastically increase application
performance.  Because the EJB container can share stateless session bean
instances across all EJB clients, it can maximize performance, as well as
cache the instances in some cases.

"...Finally,...(A)lthough the bean doesn't persist across requests, it can
be used multiple times over one request and bean lookup.  For this reason,
multiple methods that operate on the same logical data can be consolidated
into a single bean.  This can really clean up code and clarify what
different components are used for.

"...I've emphasized this quite a bit, but I'll say once more that you don't
want to use stateful session beans for many of [your] business
processes...."

Java Enterprise Applications, Volume I: Architecture, pp. 22-23.

Further, Sasha Nikolic doesn't even discuss stateful session beans,
recommending that for most uses, a session facade using stateless session
beans or a singleton cache (possible using a HashMap) are the preferred
methodologies.

Java Enterprise Best Practices (O'Reilly 2003): 7-31, esp., 10-13 and 22-24.

As for Brett's experience, he's "been working in computers since the Logo
days.... He has spent the last several years implementing [Java-based
application infrastructures] at Nextel Communications and Allegiance
Telecom, Inc.  Brett is one of the cofounders of the Java Apache project
Turbine....  He is also a contributor to the EJBoss project...and Cocoon....
His projects all focus on using XML and the J2EE platform in
mission-critical, high-performance, distributed systems.  Together with
Jason Hunter, he has defined the JDOM API....

Java Enterprise Best Practices (O'Reilly 2003): Chapter 5 and p. 266.

Brett also defined the Struts framework and is presently lead architect for
the Apache Tomcat project.


Mark


  -----Original Message-----
  From: Victor Langelo
  Sent: Tuesday, December 09, 2003 12:15 PM


  Well, I've never read Brett McLaughlin's book. I doubt I'll go out and buy
it based on what you've told me so far. What exactly is his reasoning for
saying stateful session beans are so heavy that you need to avoid them in
cases where they are perfectly appropriate?

  Based on Mr. McLaughlin's resume, I've been designing/coding applications
a lot longer. Unfortunately too many people pay far too much attention to a
person's credentials instead of reasoned arguments backed up by actual
experiments. Does Mr. Laughlin's book include actual test cases which
demonstrate his point?

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