| RE: [aspectj-users] Aspect Weaver |
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Weaving in AspectJ-1.1 is designed to play well with Java’s existing modularity. Let’s assume that your system has a tracing module that includes several aspects and a large number of pure Java modules A, B, …, Z.
Your build process needs to first build the tracing module and write it into tracing.jar. As you’d expect, this .jar will need to be rebuilt when and only when code in the tracing module is changed.
If you make a change to module B you will need to recompile that module in the same way that you would in a pure Java world. You have two choices for how to make sure your aspects are applied to that module. You can build your module with ajc instead of javac and use the –aspectpath option to ensure that the aspects in tracing.jar will be applied to the resulting code. If you’d prefer, you can compile module B with javac (or jikes or any other Java compiler) and produce a pure java unwovenB.jar file – this has the advantage of being able to use your existing build process with the least changes. You will need to add a final step to your module’s build process that will use ajc to apply tracing.jar to unwovenB.jar and produce the final B.jar.
Note: if you use the simple support in ant to only recompile individual .java files whose source has been changed, you could in theory combine this with ajc to also just reweave those same files. There are some subtle issues with this approach, but if you’re comfortable with the problems that the ant solution has for pure Java systems, ajc shouldn’t add any new issues to a design like this.
As we mention in the paper, a completely different solution to this problem is to perform all of the weaving at class load time instead of at build time. The 1.1 weaver implementation can support this in theory, but there’s more work to be done to make this something that is easy for developers to just use. However, I don’t believe that this approach has many benefits over using ajc in linker mode as a final step in your build process.
-Jim From:
aspectj-users-admin@xxxxxxxxxxx [mailto:aspectj-users-admin@xxxxxxxxxxx] On Behalf Of Trishan de Lanerolle
Hi Jim, Would it be possible for you to make a clarification to a comment made in the paper " Advice weaving in AspectJ". This was a question raised by one of our Architects. In section 2 "The compilation process", you mention a back-end weaving AOP which can be used to implement ClassLoaders that would weave advice into classes dynamically as they are loaded by the virtual machine. I am not sure if this relates to the question raised, however one of the concerns brought up was how does AspectJ address the builds. In a modular structure, would it dynamically pick the modules that require weaving or would it do a single monolithic build having to go though all the modules each time. I am not sure how to answer this question and would appreciate any feedback. This is a major concern with large project builds which sometimes go into several hours. So each time a change is made, would it mean a complete recompilation or dynamic update. Thank you Trishan |