Introduction to JBoss for exteNd Users

This chapter provides an introduction to the JBoss Application Server for users familiar with the exteNd Application Server. It includes these topics:

About JBoss

The JBoss Application Server is an Open Source application server written in Java. JBoss is a complete J2EE 1.4 certified implementation, supporting the full range of J2EE services. JBoss allows you to deploy applications easily to a wide range of platforms, including Linux, Solaris, Microsoft, and Unix.

J2EE services

JBoss offers full support for these major areas of the J2EE 1.4 specification:

J2EE Web Services and the Service Oriented Architecture (SOA)
Java Messaging Service (JMS)
Enterprise JavaBeans (EJB)
Java Transaction API (JTA)
Java Authentication and Authorization Service (JAAS)
J2EE Connector Architecture (JCA)
Java Authorization Contract for Containers (JACC)
JavaServerPages and servlets (provided through integration with Tomcat)

The JBoss architecture is based on a Java Management Extension (JMX) infrastructure. This infrastructure makes it possible for JBoss to integrate with a variety of external software components. These components are defined as Managed Bean (MBean) services that can be loaded into JBoss. Once defined, these components can be managed through JMX.

JBoss extensions

JBoss also includes several key features that build on the J2EE architecture:

Built-in support for the Aspect-Oriented Programming (AOP) model, which greatly improves developer productivity
Integration with Hibernate, an object persistence framework developed by JBoss
Enterprise-class clustering and distributed cache support

JBoss server configurations

JBoss supports several server configurations out of the box:

The all configuration starts all of the services, including clustering.
The default configuration starts all J2EE services using the JBoss optimized class loader. Since the components are deployed in the same Java Virtual Machine (JVM), this configuration results in the best performance. However, the deployed applications are not fully compartmentalized in this configuration.
The minimal configuration starts the JBoss microkernel, as well as the JMX MBean server and the JNDI naming service.

Custom configurations You can also develop your own custom server configurations. For example, you might want to make a copy of the contents of the all configuration (jboss-4.0.x\server\all) and name the custom configuration exteNd. In this case, you would modify the configuration files under \jboss-4.0.x\server\exteNd to satisfy your own application or performance requirements.

NOTE: To run the custom exteNd configuration, you would issue the command run - c exteNd.

Where to find more information on JBoss

Here's a list of useful links to the JBoss documentation:

For more information For introductory material on the JBoss application server, see Getting Started with JBoss 4.0.

For more information For complete information on configuring and managing the server, see The JBoss 4 Application Server Guide.

For more information For details on what's changed in Version 4, see What's New in JBoss AS 4.0.

JBoss and the exteNd Application Server compared

This section presents a feature-by-feature comparison of JBoss and the exteNd Application Server.

	JBoss	exteNd Application Server
Architecture	Pluggable architecture, based on JMX.	Fixed architecture.
Server repository	File-based.	Requires a database.
Server configuration	Configured through a set of XML files in the JBoss file structure. These files are grouped in several configuration sets: all default minimal	Uses SMC and SilverCMD for server configuration.
Server management	Can be managed through any JMX-compliant management application. At installation time, JBoss includes the JMX Management Console for server management.	Uses SMC and SilverCmd for server management.
Registry	Does not use the Windows registry, making it easy to maintain several installations on the same system.	Uses the Windows registry for some settings, which it's difficult to maintain several installations on the same system.
Web container	Web container is a pluggable MBean. By default, JBoss is integrated with Tomcat.	Installs a built-in Web container.
Java environment	Requires a pre-installed Java Development Kit (JDK).	Installs its own version of the Java Runtime Environment (JRE).
Classloading	Uses a flat class loading model. All classes are loaded by the same classloader. If applications cannot share classes because of version conflicts, you need to scope the classes. For more information on classloading in JBoss, see Classloading issues.	JARs in AGCLASSPATH variable and AgJars.conf file are loaded by the system classloader. Each application (EAR or WAR) has its own classloader.
Clustering	JBoss has clustering built in and enabled in its all configuration. JBoss also uses JavaGroups, which allow developers to create reliable multicast applications without making code changes.	Clustering components (Cache Manager, Load Manager, and Dispatcher) are available with certain editions of the application server. Clustering requires more work to configure.