Your next version of the JBoss Application Server will come in a variety of flavors. In effect, Red Hat wants to supply slimmer versions as well as its full-bore Java Enterprise Edition version.

That's a departure for the first open source Java application server. The initial goal of the JBoss team was to build an open source equivalent to IBM's WebSphere or BEA's WebLogic, now part of Oracle. JBoss succeeded, and like WebSphere and WebLogic, its app server became big and complex. In the meantime, lighter technologies are coming to the fore, such as the Spring Framework, Ruby on Rails, and Google Web Toolkit.

"If you're using a lightweight deployment of Spring, then JBoss brings a lot of baggage along" that's not needed to run a Spring application," said Craig Muzilla, VP of middleware at Red Hat.

Spring is a framework for producing Java applications that avoid complex Enterprise JavaBeans and run with the lightweight SpringSource dm Server. With competition like Spring and the more modular Geronimo from the Apache Software Foundation coming along, Red Hat decided to rearchitect JBoss. It's spent much of the last three years doing so, Muzilla said in an interview at JavaOne.

Customers of JBoss' upcoming 5.0 version will get to choose from one of three configurations in what Red Hat calls its JBoss Open Choice strategy. The 5.0 releases are currently available only in early access, with no date set for general availability.

The JBoss Enterprise Application Platform 5.0 is closest to the existing 4.3 release of the application server, capable of running Java Enterprise Edition and loaded with enterprise services, including clustering, data caching, messaging, transactions, and a full Web services stack. It's been rearchitected so the core Microcontainer, or application-managing heart of the application server, can be separated from the APIs and enterprise services surrounding it. It's a more modular makeup following OSGi principles for managing Java software, Muzilla said.

A second configuration, JBoss Enterprise Web Platform 5.0, is a slimmed-down version. It's still built around the Microcontainer and it can still be clustered, but it includes simplified Web services following the Java EE Web Profile, which calls for Java Server Pages and Enterprise JavaBeans 3.1 to be available but eliminates other services.

A third profile is JBoss Enterprise Web Server 5.0, a slimmest version yet for running lightweight Java workloads on the Apache Web Server. Such workloads rely on "plain old Java objects" built in Java Standard Edition instead of invoking Enterprise JavaBeans with their complex APIs. It's aimed at simple Web applications with common connectors to databases and other Web site components.

The Web Server profile is meant to load just the parts of the application server needed to run a particular Web application, simplifying deployment and speeding operations, Muzilla said. The approach reflects the popularity of the Apache Software Foundation's Tomcat, a lightweight application server frequently used on the Web that's designed to do nothing but run Java Servlets -- short Java programs that deliver a well-defined service.

"Customers are looking for alternatives to costly, bloated, and complex software," Muzilla said.

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