# JBoss AOP - User Guide

The Case For Aspects
1.1

## Preface

Aspect-Oriented Programming (AOP) is a new paradigm that allows you to organize and layer your software applications in ways that are impossible with traditional object-oriented approaches. Aspects allow you to transparently glue functionality together so that you can have a more layered design. AOP allows you to intercept any event in a Java program and trigger functionality based on those events. Mixins allow you to introduce multiple inheritance to Java so that you can provide APIs for your aspects. Combined with JDK 5.0 annotations, it allows you to extend the Java language with new syntax.

JBoss AOP is a 100% Pure Java aspected oriented framework usuable in any programming environment or as tightly integrated with our application server.

This document walks you through how AOP can be used to build your applications. A large number of real-world examples are given in each section to illustrate various ideas. The book is broken up in the following manner:

What is an Aspect?

  The section gives an overview on exactly what Aspect-Oriented Programming is.

Terms

  Defines some basic AOP terms that you will need when reading this document.

Building Aspects

  The chapter walks through some examples of building an aspect. One example shown is how to detect JDBC connection leakages in your code. Another example is using the Observer/Observable pattern Another is doing dependency injection.

Aspect-Oriented Annotations

  This chapter walks through how you can use JDK 5.0 annotations and AOP to actually extend the Java language with new syntax. Numerous real-world examples are given.

Mixins and Introductions

  This chapter walks through how you can use AOP introductions and mixins to have aspects with APIs, or how to extend a POJO's functionality transparently. Specific examples are an Asynchronous framework and making a POJO into a JMX MBean.

Dynamic AOP

  This chapter walks through how you can use the dynamic per-instance API that each aspectized class has to define aspects on a per instance basis rather than for every instance of a class.

Integration with Pointcuts

  This chapter steps away from writing aspects, but rather talks about how you can publish pointcuts that can be used by users/customers to integrate with your products.

Testing with AOP

  This chapter shows how you can use AOP to test your applications in a easier way.

If you have questions, use the user forum linked on the JBoss AOP website. We also provide a tracking links for tracking bug reports and feature requests. If you are interested in the development of JBoss AOP, post a message on the forum. If you are interested in translating this documentation into your language, contact us on the developer mailing list.

Commercial development support, production support and training for JBoss AOP is available through JBoss Inc. (see http://www.jboss.org/). JBoss AOP is a project of the JBoss Professional Open Source product suite.

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&aopide;