On Mar 23, 2009, at 12:46 PM, Scott Hernandez wrote:
>
> And everything is fine, but if I add another Queue (in resin-web.xml)
> then I get a problem as I have more than one Queue and it is not
> unique for injection. Now, in the examples it shows using
> @Named("QueueName") but that annotation cannot be applied to a field
> as the example seems to indicate.
>
> @Named("userUpdates")
> private BlockingQueue userUpdateQueue;
>
> How do I differentiate between the queues in my injection annotations?
The docs are a bit out of date, because the Java Injection spec has
changed a bit from the earlier draft. "@Named" is now _only_ for EL
naming, not for binding.
In this case, you're supposed to create your own @BindingType
annotation, @UserUpdates. So you inject it like:
@UserUpdates
private BlockingQueue userUpdateQueue;
And you configure it like:
<jms:FileQueue>
<Named>userUpdates</Named>
<mypkg:UserUpdates xmlns:mypkg="urn:java:com.me.mypkg"/>
</jms:FileQueue>
(I'd put the xmlns:mypkg at the top in a real config file.)
Creating the annotation is a little bit of extra work but has the
following advantages:
1. it's "type safe", i.e. the compiler (and Java Injection) can
verify the @UserUpdates is a valid @BindingType annotation, e.g.
saving you from typos.
2. it's documented by JavaDoc, so you can explain the purpose of
the @UserUpdates
3. it fits into IDEs, because IDEs have access to the annotation
and to the xmlns of your configuration
4. it gives you a chance to think carefully about the organization
of your components, in this case to double check that "UserUpdates" is
a logical and self-documenting description of the queue you're using.
The UserUpdates annotation is defined like:
package com.me.mypkg;
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import javax.inject.BindingType;
@BindingType
@Target({TYPE,FIELD,METHOD,PARAMETER})
@Retention(RUNTIME)
public @interface UserUpdates {
}
(Resin does have a com.caucho.config.Name for generic things like
databases, but that kind of general annotation is discouraged.)
-- Scott
>
>
> Thanks in advance,
> Scott
>
>
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