IndicThreads >> What are the striking features of JBoss Application Server 4.0 that was released recently?

Anil Saldhana >> The striking feature of JBoss v4.0 is that it has passed the J2EE 1.4 Compatibility Tests from Sun Microsystems. It was 8 plus months of focused effort, reiterating our commitment to the community and our customers-to provide quality software that is low cost as well as standards certified. JBoss v4.0 includes support for AOP and J2EE Web Services. It has JBossCache, Tomcat 5, Hibernate and Clustering support while providing our usual JMX support among host of other services.

JBoss v 4.0 has the following new features:

• Supports J2EE Web Services including JAX-RPC (Java API for XML RPC) and the Web Services for J2EE Architecture, which facilitates exposing stateless session beans as Web Service endpoints. JBoss V3.x contains a proprietary Web Services stack called JBoss.Net (which is deprecated).
• Implements the EJB 2.1 specification. The EJB 2.1 specification extends the message-driven bean contracts to support other messaging types in addition to JMS. It supports stateless session beans as web service endpoints. It also includes a new container managed service called the EJB timer service.
• Implements the JMS (Java Messaging Service) 1.1 specification instead of the JMS 1.0 in JBoss AS 3.2. In JMS 1.0, client programming for the Point-to-Point and Pub/Sub domains was done using similar but separate class hierarchies. In JMS 1.1, there is now a domain-independent approach to programming the client application. JMS1.1 includes a combined model of Queue/Topic connections that can be used for both styles.
• Implements the JCA (Java Connector Architecture) 1.5 specification instead of the JCA 1.0 in JBoss AS 3.2. The JCA 1.5 specification adds support for the life cycle management of resource adapters, worker thread management as well as transaction and message inflow from the resource adapter to the application server.
• Implements the new Java Authorization Contract for Containers (JACC) specification. JACC is a Java 2 permission-based mechanism for externalizing the authorization decision for accessing EJB methods and web resources.

IndicThreads >> Talking of Aspect-Oriented Programming (AOP) Model, can you tell us more about AOP? What is AOP and how has JBoss used it?

Anil Saldhana >> I would direct the readers to an article written by Bill Burke called ?It?s the Aspects? available at (http://www.sys-con.com/story/?storyid=38104&DE=1) . To describe it in a simple statement, AOP provides the ability to add different behaviors to your code at runtime, via aspects and pointcuts. AOP practitioners define crosscutting concerns as the behavior that is cutting across multiple points in your object model, and yet is distinctly different from the classes it's crosscutting.

"In a simple statement, AOP provides the ability
to add different behaviors to your code at runtime,
via aspects and pointcuts."

Lets take an example - you would like to time how long each method in an object takes at runtime. Without AOP, you would instrument the code with timing code. You will have to do this for every method. But AOP will allow you to do dynamic instrumentation of the code. Now this was just timing. What if you want to add auditing/logging code to every method? It is the same process of instrumentation without AOP. But AOP allows you to add aspects (like metrics, audit etc) to the code at runtime.

JBoss AOP is a 100% pure Java aspect oriented framework usable in any programming environment or tightly integrated with our application server.

"JBoss AOP is a 100% pure Java aspect oriented framework
usable in any programming environment
or tightly integrated with our application server."

Aspects allow you to more easily modularize your code base when regular object oriented programming just doesn't fit the bill. It can provide a cleaner separation from application logic and system code. It provides a great way to expose integration points into your software. Combined with JDK 1.5 Annotations, it also is a great way to expand the Java language in a clean pluggable way rather than using annotations solely for code generation.

JBoss AOP is not only a framework, but also a prepackaged set of aspects that are applied via annotations, pointcut expressions, or dynamically at runtime. Some of these include caching, asynchronous communication, transactions, security, remoting, and many more.

JBoss AOP is currently integrated with JBoss IDE and there is an animated demo available at http://docs.jboss.org/jbosside/jboss-ide-aop-demo.