Question

I have an application using AspectJ with load time weaving to advise various methods. I would like to put a switch in my program to disable the aspect without having to make any source code changes or having to restart the program. It needs to incur as little overhead as possible while turned off. Thanks!

Answer 1

To my knowledge, there is no way to unweave some advice from bytecode. If you’re working with an existing piece of augmented bytecode, I don’t believe there’s any way to remove it other than restarting the application without the weaving*.

If you’re talking about setting things up so they can be removed – it may be true that the weaving can’t be removed, but you could certainly add a global if (useWeavedCode) check around all of it, and of course add that variable as well as methods to modify it in an appropriate way (expose via JMX, new console command, new admin JSP page, etc.). Then if you want to prevent this new behaviour, you can disable it with this new option.

Note of course that this doesn’t actually remove the code, and incurs the cost of a boolean
parameter lookup while it’s disabled, but I don’t think it’s possible to do better than that.

*Strictly you need to get the class loaded again, so you don’t need to restart the app, but in practice this is likely the most straightforward option available to you unless you’ve previously put hooks into the classloaders.