BEA has released the latest version of its application server, WebLogic 9.0.

This latest incarnation of comes replete with updates to the kernel, support for multiple programming models, and more focus on operations, administration, and management.

New side-by-side upgrades enable sysadmins to install new J2EE-based applications and "gracefully migrate users to the new app," said marketing VP Bill Roth. "You get the ability to turn the dial on how many users move from one version to another." Administrators can roll back to the original version, he added.

Also included are "hot patch" features that let you upgrade servers in a cluster without any downtime. WebLogic 9.0 developers can now also use the Spring Framework and Apache Beehive. "Our developers are telling us that they are using additional models to J2EE and often they're blending J2EE with Spring," Roth explained.

A Diagnostic Framework enables you to look inside applications while they are running. WebLogic 9.0 also features a new interface, Roth said. "Administrators now have a My Yahoo-like ability to administer the server," he said. "It's very customisable."

BEA is billing the release as a step forward for businesses that want Service Oriented Architectures (SOAs). An industry analyst aid BEA has more work to do though. "WebLogic 9.0 is interesting in terms of flushing out support of SOA, but BEA needs to deliver on some of the longer-term announcements they talked about around AquaLogic earlier this quarter. Once that happens, their SOA offerings will be more complete," said Steve Garone, senior analyst at Ideas International.

When it comes to application server stacks, "the most important new features to customers are high-availability and transaction management," said IDC analyst Dennis Byron.

Although technology-wise BEA is typically one to two years ahead of its competitors - IBM, Oracle, and Sun - one cannot compare the stacks against each other, said Byron. IBM for example offers the best products on mainframes, while BEA's software dominates on Linux.

Which application server is actually the best choice "all depends on what the user needs in terms of industry, operating environment, high-performance, high-availability, newer programming paradigms, standards, and integration with other features like portals," Byron said.