Dynamic proxy causes downstream code to not find annotations. How to solve?

From:
rupertlssmith@googlemail.com
Newsgroups:
comp.lang.java.programmer
Date:
Mon, 16 Mar 2015 05:10:42 -0700 (PDT)
Message-ID:
<9a31318b-4de7-42cb-9d29-202a973ae557@googlegroups.com>
Hi,

Consider this class:

class MyClass {
    @MyAnnotation
    public void myMethod() { ... }
}

Which is coerced to this interface:

interface SomeIterface {
    public void myMethod() { ... }
}

If downstream code is looking for "MyAnnotation" it will not find it when u=
sing a dynamic proxy.

Here is a "default" dynamic proxy, which effectively does nothing except to=
 call the method and report its exceptions as normal:

   public Object invoke(Object proxy, Method method, Object[] args) throws =
Throwable {
        try {
            return method.invoke(obj, args);
        } catch (InvocationTargetException e) {
            throw e.getCause();
        }
    }

The problem is that when invoke is called the Method passed to it is the on=
e from the interface, not the object, so it is SomeInterface.myMethod(), wh=
ich does not have any annotations.

What I want is to try to match the method on the actual object being proxie=
d, or perhaps some specific interface that I have identified, and effective=
ly "lift" the actual method being invoked, to being that one.

I am running into this problem because I am using the client proxy from Jer=
sey, which uses a dynamic proxy to create a REST client for me, given an HT=
TP endpoint and an interface. The problem is that when you call it, it chec=
ks that there is a @Path annotation on the method being called, and in this=
 case that method is on a different interface, and it fails to find the ann=
otation. So I need to make sure that I call it with the method from the cor=
rect interface.

Any suggestions? A problem you have run into before? Thanks for your though=
ts.

Rupert

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