Generics support for bean references

[jpechanec]

Hi,

I was thinking about invocation of services with 'interface.esb' from Java code. Right now (if I understand it correctly) I need to create an interface with a single method and typed parameter and return value so I can do something like this in the code

interface ServiceA {
     public MyClass process(String msg);
}

@Reference ServiceA service;

MyClass o = service.process("this is message");

Whenever I would need different types used (and have transformes behind the scenes do the work) I would need to define a new interface.

Do you think that it would be useful feature to provide support for constructs like this?

interface EsbService<I, O> {
     public O process(I msg)
}

@Reference EsbService<String, MyClass> serviceA;
@Reference EsbService<String, String> serviceA2;
@Reference EsbService<ClassA, ClassB> serviceB;

J.

[rcernich]

Hey Jiri,

It should be easy enough to test out to see.  Keep in mind that references are injected based on the raw type if a name is not specified, so you should use the following form when you test:

@Service(value=EsbService.class, name="ServiceA")
public class ServiceA implements EsbService<String, MyClass> {
     public String process(MyClass msg) {
          // do something
     }
}


@Reference("ServiceA") EsbService<String, MyClass> serviceA;
@Reference("ServiceA2") EsbService<String, String> serviceA2;
@Reference("ServiceB") EsbService<ClassA, ClassB> serviceB;

When I get some time, I'll try to test it out myself.

Best,

Rob

[jpechanec]

Hi Rob,

sorry for not explaining it properly. I meant a little bit different scenario.

Let's suppose we have 2 camel services, each with interface.esb interface. If I would want to call those services  from Java code using @Reference then I'd need to provide two Java interfaces that would conform to input/output message formats. My idea was to provide generalized interface that could be used for access to any such service - technically we can speak about access to BPM and other service implementations as well.

[rcernich]

Hey Jiri,

You do not need to declare distinct interfaces for each service.  The services themselves are named.  The default name for a service declared using @Service or injected using @Reference is the simple name of the class, but you can specify a name for the service, as in the code snippet above.  This is known to work.

The only question is whether or not a service can be declared using generics (which I suspect is OK, but haven't actually tested).

Best,

Rob