How to calculate bridge method target...

Question

Generics bring in a lot of goodness to java but they also mean trouble because of the introduction of bridge methods which mean its not easy to locate a method given a name and target because erasure and bridge methods mean clients actually use the bridge rather than the target.

Return types from methods have been omitted because they are not important for this quetion...

class Super{
}

class Sub extends Super{
}

interface Interface<T extends Super>{
   method( T t ); // erased -> method( Super super );
}

interface Interface2 extends Interface<T extends Sub>{
   method2( T t ); // erased -> method2( Sub sub );
}

class Concrete implements Interface2{
   method( Sub sub );     // erased to method( Super super);
   method2( Sub sub );
}

how can i programmatically determine that Concrete.method(Super) ends up calling Concrete.method(Sub) ? I would like to avoid calculations based on parameterised types and what not as this gets complicated fast...

I have looked at Springs BridgeMethodResolver but its quite complex and does a lot of stuff, surely theres an easier way.. perhaps theres not..

Answer 1

What came to my mind is:

• find all possible variants of method arguments, (using .getSuperclass()) with the final one being (Object, Object, ...)
• loop through all these and find the one that isnt Method.isBridge();

But this is again too much work, and it might not work :). I'd propose doing just:

Method target = new BridgeMethodResolver().findBridgedMethod(bridgedMethod);

No matter what the complexity is there, it's hidden from you.

If you don't want dependecy on spring, just copy-paste the code of that class.

Answer 2

I faced a related problem - I needed to retrieve annotations of the "original" method, and found it very hard to find out the method because of the bridges (which don't have the annotations). I ended up submitting an enhancement request which is accepted. In your case I don't know what you need the method for, so unfortunately, the request (as it is now formulated) may not help you.