AspectJ in Spring: CTW vs LTW

Question

Question regarding AspectJ in Spring: CTW vs LTW. What's the difference? As far i understand the both approaches make the same - they both are producing java class with incorporated aspect logic instead of original class. CTW do it during compile time, LTW do it during JVM loading classes. Could you please explain any other diff between them? Thank you in advance!

Answer 1

First of all, AspectJ is independent of Spring. It was invented before Spring and does not need any frameworks. Maybe you are unaware of the difference between Spring AOP (based on dynamic proxies) and AspectJ (based on byte code instrumentation). By default you would not use CTW or LTW in Spring but just simply Spring AOP. Only if this "AOP lite" approach is not powerful enough for you, you will use the full power of AspectJ with or without Spring.

Please read the Spring AOP manual in order to learn how to use it. There is also a chapter on AspectJ there for you to study.

Concerning the basic technical differences with between types of AOP like CTW, LTW, proxy-based incl. pros and cons, see my answer there. @Moderators: I really do not want to quote myself here, but also not flag this question as a complete duplicate.

Answer 2

I tried to use LTW a long time ago and it had some bugs as sometimes on startup it failed to do the weaving which is pretty bad and I decided to use CTW from then on.

LTW increases startup time but is probably easier to debug in intellij/eclipse while with CTW debugging might be hard to setup sometimes.

But as I said CTW is safer for me - classes are there ready to go, no surprises during startup/runtime. So if you do not do dynamic class loading (like in OSGi or similar) and want to weave that code with aspects then I would stick to CTW.