Worth Reading:
Article Series "AOP@Work" Started by IBM

IBM has started a new article series dedicated to the AOP theme on its “developerWorks” Web site. The article series targets developers with an AOP background, who want to deepen their knowledge. It started with two related articles from AOP guru Mik Kersten.

Within the “Java Technology“ section of IBM’s well-known “developerWorks” Web site the new article series “AOP@Work” has just begun. It focuses on the practical usage of currently available AOP techniques. Two articles from Mik Kersten have already been published. In the AOP scene, Mik gained attention as developer of IDE support for AspectJ. In both articles he presents an in-depth comparison of the four most mature AOP tools: AspectJ, AspectWerkz, JBoss AOP and Spring AOP.

"While there are major syntactic differences among the tools' aspect declaration style, the core AOP semantics are similar. Each tool has the exact same notion of a join point model, treating join points as principled points in a Java program, pointcuts as a mechanism for matching join points, and advice as a mechanism for specifying what to execute when a pointcut is matched."
(M. Kersten, in the article “AOP tools comparison, Part 1")

The selection of the four tools is based on access statistics for user lists and forums for these tools. A constant high number is regarded as an indicator for a certain product maturity. Mik, participating in the development of AspectJ, calls for objectivity. This goal is simplified because of the planned merger of the projects AspectJ and AspectWerkz. Nevertheless – his analysis is absolutely worth reading. A main result is an increasing convergence of the discussed tools on a conceptual level. Among experts a range of concepts are evolving that are generally regarded as being part of AOP.

"All of the tools are maturing at a fast pace, and many of the trade-offs discussed here are being addressed by current implementation efforts. What is even more interesting is that the strengths of some approaches are percolating out to others. For example, the crosscutting views that were once particular to AspectJ are now offered by JBoss AOP and could soon be offered by the other tools, as well."
(M. Kersten, in the article “AOP tools comparison, Part 2")

While the first article discusses the language mechanisms of the four technologies, the second one focuses on their integration into development environments. This would not have been of any interest 10 years ago, but has a large impact on tool choices nowadays.

Mik’s expectations concerning the importance of performance for future programming techniques is, by the way, quite interesting. Herb Sutter (see our first newsletter message) certainly has a different opinion about this matter:

"In the long term, performance should become a nonissue. Just as developers do not worry about the overhead of a virtual method dispatch, they will not worry about the invocation overhead of advice. This is true to a large extent now, and will get even better as weavers improve and become more tightly integrated with JITs and VMs."
(M. Kersten, in the article “AOP tools comparison, Part 2")

Concerning the convergence of the tools, the second article makes equivalent observations as the first one: Even for the integration within IDEs there is an increasing number of commonalities of the tools discussed. This insight, related to concepts as well as to the IDE integration question, indicates a growing maturity of the whole area of Aspect-Oriented Programming. The formerly exotic technique is now well on the road to become mainstream.

You will find the two articles from Mik Kersten here:
http://www.ibm.com/developerworks/java/library/j-aopwork1
http://www.ibm.com/developerworks/java/library/j-aopwork2