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JBoss, Geronimo, or Tomcat?

Three open source Java application servers compared

By Jonathan Campbell, JavaWorld.com, 12/11/07

Page 2 of 4

Java EE 5 compliance

Java EE compliance is an important issue if your enterprise Java applications must be fully compatible with Sun's Java EE 5 server features. Geronimo 2 is the only one of the three servers that is fully Java EE 5 compliant. JBoss 4.2 supports most Java EE 5 features, and Red Hat will soon release JBoss 5, which will be fully compliant with Java EE 5. Tomcat is a JSP/servlet container that supports only basic Java application server features.

EJB 3 (Enterprise JavaBeans) capable

Enterprise JavaBeans (EJB) is a Java component architecture for application development on Java EE servers. It allows you to package functionality into reusable components. Earlier versions of EJB are considered to be difficult for development, even though it was intended to be a development advantage. The new EJB 3 is supposed to solve the difficulties associated with earlier versions and offer some new functionality. Both JBoss 4.2 and Geronimo 2 support EJB 3. Tomcat 6 by itself does not offer EJB 3 compatibility, but the Apache OpenEJB project can be embedded in Tomcat for EJB 3 support. According to Jeff Genender of the Apache Software Foundation, Tomcat can also run an embeddable version of the JBoss EJB 3 container.

JSP 2.1 and Servlet 2.5 capable

JSP/servlet features are the most basic capabilities for any Java server. JSP 2.1 and Servlet 2.5 are the new Java EE 5 versions of JSP/servlet capabilities. JBoss 4.2, Geronimo 2, and Tomcat 6 all support these new JSP/servlet versions.

JSF 1.2 support

JavaServer Faces is a Java EE application-development architecture that makes development of Web-based user interfaces easier. Instead of a request-driven MVC (model-view-controller) architecture, JSF uses a component-based approach. JSF 1.2, the current version, is supported by JBoss 4.2 and Geronimo 2. JSF 1.2 runs on Tomcat 6 but problems have been reported.

Custom plug-in support

Plug-in support refers to an architecture for incorporating new functions and features into the server. JBoss calls its plug-in development features MBeans (managed beans), and Geronimo has similar functionality, called GBeans. These custom beans provide a set of interfaces for developing and managing custom resources that can in turn be reused as plug-in components.

Geronimo takes plug-ins a step further, according to Jeff Genender:

With Geronimo, you can pick and choose from a plethora of components to build an application-server stack that fits your needs. For example if you wanted to install the Liferay portal, or Apache Directory server, you would add the URL in the management console and install the plug-in over the Net. The plug-in management system retrieves all of the dependencies that are needed and installs those as well.

Geronimo also has custom assemblies, which Jeff summarized as

[t]he ability to make an application as light or heavy as you want it. You can use the full Java EE 5 stack which includes all the components, or you can use Little G, which is just Geronimo with a Web container, or Micro G [...] which is just the Geronimo kernel and a perfect base for SOA and ESB solutions. You can add and remove components, providing only the ones you want to make use of. If you don't need EJB, you can simply remove the component from the console.

Chantal Yang of Red Hat says that JBoss 4 offers the advantage of an application server built "from the ground up using a micro-kernel architecture." According to Yang, this enables JBoss to "plug in a variety of components to create a custom application server footprint."

Yang also stated that JBoss 5 and its micro-container will greatly improve on the plug-in support of MBeans. According to Yang, no other application server has "such an evolved POJO-based micro-container at its heart."

Business-rules engine support

Most every application is built around some set of business rules, also called business logic. A business-rules engine component can make business-logic programming much easier to manage. In most programming, the if/then basic logic is all you have to work with. A business rules engine lets you implement much more intelligent logic with ease. JBoss 4.2, Geronimo 2, and Tomcat 6 support Drools, a popular, standards-compliant, and powerful business-rules engine. Although Geronimo is a fully Java EE 5 certified server that can run Drools, JBoss has provided Drools support for three years as of this writing, making JBoss/Drools a stronger business-rules solution. JBoss has recently rebranded Drools, naming it JBoss Rules. The Drools project itself started in 2001.