Aop lost when bean moved to parent injector

[Vyacheslav Rusakov]

Hello,

Test ng guice support creates implicit parent injector and creates child injector for your module. So parent injector is out of my control.

If bean has no specific dependencies to other beans in child injector it would be created in parent injector, even if this bean is declared in child injector's module.

I understand this behaviour is by design to solve probles with JIT.

But when such bean moves to parent injector, aop interceptors, defined in child injector, can't affect such bean anymore.

I know that common recomendation for such case is to disable JIT, but I don't want to do it (too radical solution).

Is there any workaround to tie bean to child injector without introduction of some dummy (anchor) dependency on it?

[Tavian Barnes]

bind(SomeBean.class);

in the child module will force it to stay there.

[Vyacheslav Rusakov]

Thank you for answer. You forward me to right direction. I did simple test and it appear that there is a thin moment:

When you have:

bind(IBean.class).to(BeanImpl.class)

And you inject bean as IBean, then it will be created in parent(!) injector.

But it will create bean in child injector if implementation is also binded.

bind(IBean.class).to(BeanImpl.class)

bind(BeanImpl.class)

It would be interesting to know "the why" for such behaviour.

вторник, 23 июня 2015 г., 20:05:25 UTC+6 пользователь Tavian Barnes написал:

[Tavian Barnes]

https://github.com/google/guice/issues/888 describes the general issue and a potential workaround in Guice 4: if you requireExplicitBindings(), it will prevent linked bindings from "bubbling up."

[Sam Berlin]

https://github.com/google/guice/issues/935 is open about the different behaviors between requesting the interface vs requesting the impl... There shouldn't be a difference in behavior, right?

sam

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[Tavian Barnes]

That looks like "notabug" to me.  In those examples it's not just the requested type that differs, but how it's bound as well:

bind(ITestAop.class).to(TestAopImpl.class).in(Singleton.class);
ITestAop test = injector.getInstance(ITestAop.class);

vs.

bind(TestAopImpl.class).in(Singleton.class);
ITestAop test = injector.getInstance(TestAopImpl.class);

[Vyacheslav Rusakov]

I think this behaviour is at least confusing.

When you define bean like this

bind(ITestAop.class).to(TestAopImpl.class)

You expect that its correctly binded, but guice create implementation instance following JIT beans rules (its not obvious).

I tend to think that it's not correct behaviour, especially if you inject such type as an interface (ITestAop).

I can understand if guice will create JIT binding if I use the implementation for injection because implementation type is indeed not binded. 

But this type of problems at least has a workaround (to bind also the implementation).

Guice perfectly works with dependency graphs. Even counting bindings bubbling its totally ok because everything works fine.

But it completely lacks aop hints: if you have bean without dependencies and use JIT binding for it it will bubble up which is ok.

But aop, you expect to be working isn't working anymore.

There must be an option to specify aop requirement hint for dependency to let guice count it as dependency too when it decide to bubble.

Something like: bindAopHint(Matcher.annotatedWith(Transactional.class)) - all beans with transactional annotation should remain in child injector

(I understand its weak solution, but just to show the idea)

Or at least it would be great to have ability to tie binding to injector, for example, when I do

injector.getInstance(MyType.class) // injector here is child injector

MyType will be binded in parent injector (suppose it has no deps on other beans). 

But I want it to use aop of my child injector! No way to tell guice about it... (only by using redundant "anchor" dependency in bean)

четверг, 25 июня 2015 г., 5:40:30 UTC+6 пользователь Tavian Barnes написал:

[Tavian Barnes]

I don't think bindAopHint() would even be necessary.  Guice could just run all the matchers already specified with bindInterceptor() to see if any from the child would apply.  If they did then it could keep the binding in the child, or at least raise some kind of warning when it bubbles up to the parent.

But yeah everyone agrees this behaviour is confusing.  TestNG compounds the issue with its mandatory parent injector, which has personally caused me a fair amount of grief for similar reasons.

To save yourself some of that grief I'd recommend always using requireExplitiBindings().