Throwing exception in @Before, catching in @AfterThrowing

Question

I created a @Before Advice that throws an exception and tried to catch it in another @AfterThrowing, but it does not work.

If the exception is not thrown in the advice, but directly in the method, it works.

If it is thrown in the advice, the @AfterThrowing is not executed.

Why does it behave like that?

Answer 1

Because @AfterThrowing means: catch the event that an exception is thrown from within the captured method. But @Before means: do something before (i.e. outside) the captured method. So your control flow never reaches a point where it could satisfy the condition for the @AfterThrowing advice.

So either you do what Frank told you (use an @Around advice) or, if you have control over the caller as well as the callee part of the code, you could do this (quite ugly):

• @Before("execution(myMethod)") (possibly throwing an exception)
• AfterThrowing("call(myMethod)")

I have not tested it, but it should work because of this control flow:

[before call]
call(myMethod)
  [before execution]
  execution(myMethod)
  [after execution]
[after call]

I.e. "before execution" is already "within call".

Answer 2

I suppose the 2 advices are in same aspect? If not, have you declared a precedence to define the weaving order?

Anyway, if you want to do something before a method, and something after depending on what you did before, you should be using an @Around advice instead. You might not even need an exception (which is costly) to control the flow that way.