Seam2.x's @Unwrap in CDI

[sunls]

In Weld,there is no context variable. How to get @Unwrap's behaviour?

@Unwrap
public  Manager getManager(){
   ...
   return manager;
}

Thanks.

[swd847]

The easiest way to achieve this would be by registering a stateless normal scope.

This means that if you had something like:

@Produces
@StatelessScoped
public  Manager getManager(){
   ...
   return manager;
}

you will get a similar effect to @Unwrap (however the producer will be called with every invocation on the injected proxy, so it is slightly different).

[sunls]

Douglas,thanks for your reply.

There is something that I do not understand.

1.Why should registe a stateless normal scope ?

2.Is there apporach to implement Seam2.x's XML configuration,like:

public class ManagerProxy{
...
@Unwrap
public  Manager getManager(){
   ...
   return manager;
}
...
}

public class MyFilter{
Manager manager;
...
}

Components.xml

<test:managerProxy name="manager_proxy" .../>
 <test:myFilter name="my_filter" manager="#{manager_proxy}" .../>

So,variable manager is dynamically set to Manager's instance.

[tittop]

how about it if using Portable Extension? concretely:

First: create an annotation just as Seam2's @Unwrap. Then add this @Unwrap to somewhat SomeClass.someMethod. Such as

public class SomeClass {
    @Unwrap
    public OtherClass someMethod {
        return new OtherClass();
    }
}

Second: create an extension using ProcessAnnotatedType event. Something like:

public class MyExtension implements Extension {
     
       // iterate every bean to find out which bean contains an @Unwrap annotation by using reflection
    <T> void processAnnotatedType(@Observes ProcessAnnotatedType<T> pat) {
         
        Class<?> clazz = pat.getAnnotatedType().getJavaClass();
        
        for (Method m : clazz.getMethods()) {
            if (m.isAnnotationPresent(Unwrap.class)) {
                   // get the actually returned class type
                Class<?> unwrapclazz = m.getReturnType();
                pat.setAnnotatedType(unwrapclazz); // ??how to build an AnnotatedType, giving had known unwrapclazz??
            }
        }
    }    
}

[swd847]

I have just added this into weld-extensions, it is called @ManagedProducer.

The bean actually injects a dependant scoped proxy, and every time you call a method on the proxy the proxy calls the @ManagedProducer method, and then invokes the method on the returned object:

@ManagedProduer
@SomeQualifier
@Named("manager")
public  Manager getManager(){
   ...
   return manager;
}

@Inject
@SomeQualifier
Manager manager; 

The other part of the @Unwrap, where the owner component was replaced by the result of the method call is no longer relevant in CDI, you can simply put the @Named annotation on the @ManagedProducer method and give the result any name you like.

[sunls]

What's the difference between

@ManagedProduer
@SomeQualifier
@Named("manager")
public  Manager getManager(){
   ...
   return manager;
}

and

@Produces
@SomeQualifier
@Named("manager")
public  Manager getManager(){
   ...
   return manager;
}

[swd847]

@Produces injects manager once when the bean is created.

@ManagedProducer injects a proxy once when the bean is created, and every time a method is invoked on the proxy it calls getManager() again to get the current manager.

[tittop]

Stuart Douglas wrote on Jun 09, 2010 22:59:


@Produces injects manager once when the bean is created.

@ManagedProducer injects a proxy once when the bean is created, and every time a method is invoked on the proxy it calls getManager() again to get the current manager.

but how about it if that's a dependent object, or some other stuffs which cannot be proxied?