All,
There's a 3 year old issue (issue
252<http://code.google.com/p/google-guice/issues/detail?id=252>)
about Guice AOP calling an interceptor twice if there's a synthetic method
inserted into the call-chain. What does this mean? Consider the classes:
* interface HotDog { }
class NathansDog implements HotDog { }
interface Store {
HotDog cookDog();
}
class NathansStore implements Store {
NathansDog cookDog();
}*
If you have an instance of '*Store*' and call '*myStore.cookDog();*', then
you are actually calling:
* Store.cookDog()* <-- synthetic method typed to return *HotDog*
*NathansStore.cookDog();* <-- normal method, typed to return *NathansDog*
But, that only will happen if *myStore *is typed as '*Store*'. If it's
typed as '*NathansStore*', then the synthetic method is not called.
If you method matcher for an interceptor is broad, it could be called twice
for one call to *cookDog*, because of the synthetic method!
There are a few possible solutions to this, none of which are really all
that good in my opinion:
a) Do nothing
The Good: Status quo. The bug's been open for 3 years and hasn't had a
single comment, so it can't matter too much. Right?
The Bad: It doesn't feel right to call an interceptor twice for one
method.
b) Never call an interceptor for synthetic methods.
The Good: Problem goes away.
The Bad: If the interceptor was only targeting methods that returned '*
HotDog*', it will never be called at all now!
Why the bad may not be so bad: If people referenced *Store* as *
NathansStore* and the interceptor was typed to want *HotDog*, the
interceptor wouldn't have been called anyway.
c) Do some fancy footwork when building the injector & matching methods to
interceptors, and deduplicate synthetic/normal methods as much as possible
in terms of matching interceptors.
The Good: It should end up working as people would expect.
The Bad: Building the injector has to do even more work and take
marginally longer. It also leaves open the strange situation where you can
build an interceptor that only *sometimes* gets called, depending on what
the variable type of the caller is.
Thoughts?
sam
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