AspectJ

AspectJ feels natural, as if it fills in a gap in your programming knowledge rather than extending it in a new direction.

In AspectJ, an inter-type method declaration looks almost identical to a normal method declaration and is referred to in the same way.

It is possible to use both AspectJ and Spring AOP simultaneously: they do not conflict.

Note that this article addresses the implications of the recently announced merger of the AspectJ and AspectWerkz projects.

Currently, AspectJ and AspectWerkz do not include any libraries, although some third-party libraries have been created using these tools.

Since AspectJ is an extension to the Java language syntax and semantics, it provides its own set of keywords for working with aspects.

Just as the class is the unit of modularity for Java, the aspect is an additional unit of modularity for AspectJ.

The AspectJ compiler is an extension of the JDT compiler, and is therefore fully capable of compiling Java code.

At this time, the AspectJ compiler is the only commercial-quality AOP compiler, although other research-quality compilers exist.

One issue is the requirement that the AspectJ weaver be able to resolve references to third party classes contained in the jar being woven.

Every legal Java program is a legal AspectJ program, so your code will compile just as it always has.

With the AspectJ compiler, you get all the benefits of static checking that you expect from Java code, but applied to aspect code.

The power of the AspectJ pointcut expression language is not merely about allowing sophisticated constructs.

This article assumes that you are generally familiar with AOP under AspectJ and is not intended as an introduction to AOP.

We've seen how AJDT shows the crosscutting nature of AspectJ by adding editor markers and decorating advised elements.

Based on Table 1, you can see that AspectJ, AspectWerkz, JBoss AOP, and Spring AOP are the leading tools in terms of user adoption.

Method at a join point in an around advice, AspectJ handles this situation for me without requiring any special effort.

AspectJ incurs compilation overhead in terms of memory usage and time, since it performs most advice planning at compile time.

Take advantage of the @Profiled annotation and AspectJ's load-time weaving to decide which methods should be timed at deployment time.

In AspectJ, these points are called point cuts, and the code you execute at point cuts is called advice.

The next piece of the aspect uses some of the new AspectJ 5 support for matching types based on annotations.

Entries can be added to a project's inpath by right-clicking on the project, selecting Properties, then going to the AspectJ InPath section.

AspectJ is an implementation of the aspect-oriented programming model on the Java platform (see Resources).

This allows AspectJ applications to be compiled by a regular Java 5 compiler, and then later woven by the AspectJ weaver.

Ramnivas is an active member of the AspectJ user community and has been involved with aspect-oriented programming from its early form.

The Composite pattern can be implemented in AspectJ using inter-type declarations as shown above with configuration.

The process is also reversible, with a context menu entry to remove the AspectJ nature and switch back to the Java compiler.

In this final article in the AOP@Work series, I introduce you to Contract4J, an AspectJ-based tool that supports Design by Contract.

While I ve used AspectJ to develop all the code for the example, implementations in other AOP systems are conceptually identical.

This aspect is written in the Aspect language, so needs to be compiled by the AspectJ ajc compiler.

At this time, no UML viewer is compatible with AspectJ or any other AOP tool.

An important limitation to the current version of AspectJ is that its compiler can only weave aspects into code for which it has the source.

Modify your build environment, as shown in Listing 3, to include required AspectJ properties.

Using visual tools: The two patterns described here leverage AspectJ's IDE support for Eclipse, also known as AJDT.

The last three occur less often in practice for Spring users, and if they prove problematic, we recommend using AspectJ.

As you saw earlier, markers in the AspectJ editor and Cross References view clearly show you the nature of crosscutting on a per-file basis.

You want to use AspectJ's ability to declare warnings or errors to be flagged by the compiler.

An upcoming release will integrate with AspectJ to provide interoperability with fine-grained crosscutting mechanisms.

Note that at this time, AspectJ is the only tool that provides a static enforcement mechanism that employs pointcuts.

Create the AspectJ caching asset and discuss some of its customizable points.

Aspect declarations in AspectJ parallel class declaration in the Java language, as shown in Figure 2.

Whilst this overhead cannot be avoided completely, future releases of AJDT and the AspectJ compiler will focus on reducing it.

AspectJ is an extension of the Java language that lets you declare aspects entirely in code.

AspectJ comes with an Ant task, dubbed iajc, that acts like javac; however, this process compiles and weaves aspects into subject code.

With static checking, AspectJ's compiler issues a warning noting that the type name or signature could not be resolved.

Simply take a plug-in project and right-click to convert it to an AspectJ project in the same way you would a Java project.

The new programming model, leveraging AspectJ constructs, is built on top of the existing Spring AOP runtime.

In AspectJ, lots of advice can run at a join point without knowing anything about other advice at the join point.

Orbitz uses a mix of direct ERMA instrumentation and AOP-style instrumentation using Spring and AspectJ based configuration.

An aspect is AspectJ's unit of modularity and has much in common with a class in the Java language.

Contains reusable implementations of 12 of the Gang of Four patterns in AspectJ as well as in the Java language.

The contract is a Java class that implements a specific interface, and the "bridge" is an AspectJ aspect.

I expect that the overhead will drop significantly with further tuning of the Glassbox Inspector and AspectJ load-time weaving.

Note that the planned @AspectJ syntax will look very similar to the AspectWerkz annotation syntax.

In order to incorporate our aspect into the system, we add the aspect source code to the project and build with the AspectJ compiler, ajc.

Another run-time performance benefit results from static typing of join point parameters in AspectJ and AspectWerkz.

The AspectJ compiler builds AspectJ and Java code declared in ". java" or ". aj" files, and produces plain Java bytecode.

What is so amazing about AspectJ is that an aspect can be applied to an entire application without a lot of effort.

In this case, I'll combine JMX with AspectJ, which enables me to write the management logic separately.

In this case, you can configure AspectJ to use Java 5 mode either as a workspace preference or on a per-project basis.

Typical join points in AspectJ include method calls, access to class members, and the execution of exception handler blocks.

The changes also provide AspectJ developers with greater access to tooling support on the Eclipse platform.

Contains links to many AspectJ related articles, documentation, and downloads.

I certainly have found them to be useful on my other AspectJ projects.

This setting is controlled from the AspectJ Aspect Path property page and can contain either JAR files or directories.

With @AspectJ syntax, framework-specific annotations are in the aspects, not business logic.

This annotation-driven programming model was pioneered by AspectWerkz, which in early 2005 merged into the AspectJ project.

Because AspectJ is not an option for some, we offer an alternative approach in this article.

Switch from your current Java compiler to the AspectJ "ajc" compiler, which also compiles Java code.

Listing 5 shows an AspectJ source file used to enable logging on method entries and exits.

Naturally, a single article cannot hope to cover all of the enhancements to a release as comprehensive as AspectJ 5.

The AspectJ homepage: Browse the documentation, get the latest news and downloads or join the AspectJ community.

Is a contract enforcement tool that combines AspectJ and Javadoc-style annotations.

The similarity of AspectWerkz and AspectJ has allowed the two technologies to join forces.

The pointcut expression language is the same as in AspectJ's own syntax, and the semantics are identical.

An output JAR setting is also present in the AspectJ section of each project's property page.

AJDT is implemented by a growing number of plug-ins that are AspectJ-enabled.

AspectJ is perhaps the best known and most widely used AOP implementation.

The upcoming version of AspectJ will support metadata by modifying the AspectJ language.

AspectJ has a well thought out, rigorously defined and well documented pointcut language.

The AJDT project provides Eclipse Platform-based tool support for aspect-oriented software development with AspectJ.

This series of two tutorials describes in detail how to package AspectJ-based assets for use with Software Architect.

The com. ibm. aspectj. lib aspect library contribution to Aspects for MDD includes an abstract tracing aspect, JDK14Tracing.

The combined @AspectJ effort will filter many of AspectJ's tool support benefits into the AspectWerkz annotation style.

You can use any IDE or run it from command prompt using aspectj compiler to execute and test the attached source code.

Before you can create this bootstrap aspect, you'll have to download AspectJ.

The second layer is implemented using AspectJ and provides for orchestration and flow control of the process.

Similar mechanisms as AspectJ without the language extension.

AspectJ is nearly unique among AOP technologies in supporting encapsulation at this level.

An important tool provided with AspectJ is ajdoc, which generates Javadoc-style documentation for AspectJ programs.

Is a contract enforcement tool that combines AspectJ and the new Java metadata annotations.

Details are provided on the AspectJ home page and the Ant scripts that come with the distribution.

The challenge here is that this requires some knowledge of aspect technology and AspectJ syntax.

Fortunately, it is planned that the final release of AspectJ 5 will include a facility to generate these lists when compiling aspects.

AspectJ home page: Learn more about using aspects for Design by Contract testing.

AspectJ 5 will similarly support the @AspectJ syntax, which is a result of the merging of the AspectJ and AspectWerkz projects.

It's also worth noting that the AspectJ pointcut expression language offered in Spring 2. 0 has extremely powerful annotation matching.

Can AspectJ go one step further than selection to handle test configuration?

Aspect and pointcut declarations in AspectJ's code style will feel just like Java code.

The examples in this article use AspectJ, as it is the most widely known.

AspectJ is the most well documented of the AOP tools, with six books in print.

Note, however, that the steps required to use Java 5 mode in your AspectJ projects is just the same as with Java projects.

I use the Eclipse environment for development, and the AspectJ plug-in takes care of invoking the compiler with the proper arguments.

The AspectJ compiler also understands such aspects, so there is a choice of implementation strategy.

Advice in AspectJ has the same type-safety and exception checking that methods do in the Java language.

This paper use AspectJ as the AOP language, which is used to extract and implement important aspects in IDMS.

It does not discuss in any detail how to design and create AspectJ-based architectural mechanisms.

Series, I provide an overview of both AspectJ 5 the language and the AspectJ 5 release containing the AspectJ compiler and associated tools.

Contains a series of articles exploring the new features of AspectJ 5 and on aspect-oriented programming with AspectJ in general.

The second statement identifies the exact join point where the advice is executed and makes use of the AspectJ JoinPoint class.

AspectJ home page: Download the latest release and get information about AspectJ and AJDT.

Probably the most widely AOP system is AspectJ, an extension for Java.

Download the latest AspectJ compiler and tools.

To do this using AspectJ, you must compile your class and aspect code with the ajc compiler.

But in this style-called the @AspectJ model-aspects can be compiled using javac.

I need Spring to configure the aspect that AspectJ has created.

Listing 6 shows my aspect for tracking database connections using AspectJ and the JDBC API.

I've used the AspectJ declare parents form to make the PerfStats interface extend a special management interface, PerfStatsMBean.

AspectJ 5 also lets you make inter-type declarations on a generic type.

Figure 2 shows the wizard for loading the AspectJ Development Tools plug-in.

If you use a UML viewer on an AspectJ program, it will probably break because it is expecting plain Java code.

Try entering some AspectJ code in the new aspect.

AspectJ in Action (Ramnivas Laddad, Manning 2003): Discusses policy enforcement using aspects and the Observer pattern.

The other approach that has become practical with AspectJ 5 is load-time weaving.

Start-up parameter to invoke AspectJ 5 load-time weaving.

Object is identical to AspectJ s.

Note that the example code has been created using AspectJ 5.

AspectJ and AspectWerkz offer a concise way of referring to multiple types (for example, Account indicates all subtypes of an account).

You may also want to download AJDT or the command-line AspectJ compiler for use in following the examples.

If AspectJ is your AOP tool of choice, you must move to its compiler on all Java projects for which you want to enable the use of aspects.

Create an abstract AspectJ class that will be used and extended in some target project.

To learn about using AspectJ load-time weaving on earlier versions of the Java language.

To download AspectJ or the Spring framework, which you will need to follow the examples.

Secondly, there are always more features we can develop to enhance the tooling for AspectJ.

I'll also discuss the specific support for new features in AspectJ 5 and walk you through the migration process from AJDT 1. 1.

In fact, using aspects (via AspectJ, for example) is the only way to achieve this effect in the Java language (see Resources).

This is why there are two extra settings available for AspectJ projects.

So why did we choose to align with AspectJ in Spring 2. 0?

This is an age-old problem that didn't have a good solution until AspectJ arrived.

Don't want to use a special compiler such as AspectJ compiler ( ajc).

In situations like this, AspectJ applies a run-time test to see whether the argument is an

AspectJ 5 adds new pointcut designators such as @this to match based on the presence of annotations.

As an illustrate, I'll rewrite part of our earlier example, putting the pointcut in an AspectJ aspect

Annotation enabling unchecked warnings to be suppressed in a member, AspectJ supports the

AspectJ pointcut expression language support, allowing developers to apply cross-cutting security logic across their Spring managed objects

In this section, I've outlined the main trade-offs of AspectJ's language extension approach from the perspective of build integration

In AspectJ, you can use advice to provide the same guarantees but avoid locking down the order

The proposed syntax for AspectJ extends the current static crosscutting constructs to create a new

It will become an alternate way of writing AspectJ programs and be renamed to the

For a complete treatment of generics in AspectJ 5, please refer to the

Test flexibly with AspectJ and mock objects

AspectJ support - support for AspectJ load-time weaving has been added for some environments, there is also a new bean() pointcut

Check out library aspects with AspectJ 5

The key difference between AspectWerkz and AspectJ is that

Figure 1: The syntax used by AspectJ to describe pointcuts