Programmatic injection, interceptors for producers

[adamw]

Hello,

I've got in fact three questions:

1) Is there a way to programmatically obtain a current bean instance? Something similar to the Component.getInstance method in Seam. I was looking through Weld classes and docs but obviously didn't find anything.

2) I have a producer method for beans that implement an interface, let's say IMyBean. The method is:

@Produces public IMyBean getMyBean() { return new MyBeanA(); }

Is there a way to intercept calls to the methods of the produced instances? Writing:

@Produces @MyInterceptor public IMyBean getMyBean() { return new MyBeanA(); }

intercepts the factory method call, not calls to the resulting bean.

3) Finally, something I also encountered when defining the producer. If I have two implementations if IMyBean, both of them plus the result of the producer method will satisfy the injection point IMyBean. To use only the producer method, I annotated both of the implementation with @Alternative. Is there another (proper) way to tell Weld don't try to use this as bean?

Adam

[gavin.king]

Adam Warski wrote on Dec 14, 2009 22:41:


Hello,

I've got in fact three questions:

1) Is there a way to programmatically obtain a current bean instance? Something similar to the Component.getInstance method in Seam. I was looking through Weld classes and docs but obviously didn't find anything.

See here.

2) I have a producer method for beans that implement an interface, let's say IMyBean. The method is:

@Produces public IMyBean getMyBean() { return new MyBeanA(); }

Is there a way to intercept calls to the methods of the produced instances? Writing:

@Produces @MyInterceptor public IMyBean getMyBean() { return new MyBeanA(); }

intercepts the factory method call, not calls to the resulting bean.

See here.

3) Finally, something I also encountered when defining the producer. If I have two implementations if IMyBean, both of them plus the result of the producer method will satisfy the injection point IMyBean. To use only the producer method, I annotated both of the implementation with @Alternative. Is there another (proper) way to tell Weld don't try to use this as bean?

That is one good way. Another possibility is to annotate the beans @Any. We probably need to add this to the docs, since it is something people will run into very often. Alternatively, it's very easy to write a @NotInjectable portable extension that calls ProcessAnnotatedType.veto().

[adamw]

Gavin King wrote on Dec 15, 2009 02:16:

Adam Warski wrote on Dec 14, 2009 22:41:


Hello,

I've got in fact three questions:

1) Is there a way to programmatically obtain a current bean instance? Something similar to the Component.getInstance method in Seam. I was looking through Weld classes and docs but obviously didn't find anything.

See here.

But that's different - I still need to inject the Instance<MyClass> somehow. I'm asking about a situation where I'm in a non-Weld-managed instance, for example when I want to call a service from legacy code.

2) I have a producer method for beans that implement an interface, let's say IMyBean. The method is:

@Produces public IMyBean getMyBean() { return new MyBeanA(); }

Is there a way to intercept calls to the methods of the produced instances? Writing:

@Produces @MyInterceptor public IMyBean getMyBean() { return new MyBeanA(); }

intercepts the factory method call, not calls to the resulting bean.

See here.

Ok, so it's a no in my case :).

Thanks,
Adam

[william.drai]

You can do a lookup of the BeanManager in JNDI.

BeanManager manager = (BeanManager)new InitialContext().lookup("java:comp/BeanManager");

Bean<IMyBean> myBean = manager.getBeans(IMyBean.class).iterator().next();
IMyBean instance = (IMyBean)manager.getReference(myBean, IMyBean.class, manager.createCreationalContext(myBean));

But maybe there is a simpler solution.

[alexanderbell]

Be careful with such a solution becaus if you use either Qualifiers or Alternatives you get a collection of Beans in line 2. If you want to take the first bean in the colleciton the solution is ok if you don't want this behaviour it causes in a problem which is very hard to find afterwards.

[william.drai]

It seems to me that getBeans() only returns beans qualified with @Default by default.

You can get a collection of beans by querying on @Any with :

manager.getBeans(IMyBean.class, new AnnotationLiteral<Any>() {})

[adamw]

Ah, so you even can do it in a portable way - nice! :)

Although this will work only in EE.

Adam