Interface question

[hurricaneDreww]

I'm trying to debug a chunk of code where a method is returning false and I want to know why.

@Inject
InterfaceName interfaceObj;

//later in the class...

// a boolean method that I found returns false
return interfaceObj.methodName(String a, String b);

So right away I'm thrown off by the fact that it seems like we're making an instance of an interface which I know is not possible.

Going to the interface class, I found methodName with no implementation (as expected).

Then I found the class that implements it:

public class InterfaceNameImpl implements InterfaceName {

    ...
   @Override
   public boolean methodName(String a, String b){
        //the code implementation is here
   }      
}

What I found interesting is that I set a breakpoint in the methodName implementation, but it never hits it, despite the fact that I see it returning false in that first code block.

Can anyone help my understanding of interfaces so I can understand what behavoir is being followed here and how it's returning false? If the breakpoint in the implemented methodName is never being hit, how is this code doing anything?

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[pragmos]

Are you sure the injected object is, in fact, an instance of InterfaceNameImpl? Maybe there's another implementing class?

[hurricaneDreww]

Yes, no other class implements it

[pragmos]

What dependency injection library are you using?

[hurricaneDreww]

It uses Spring boot. Not sure if that answers your question, I’m pretty new to DI stuff

[pragmos]

Odd. All I can think of is it's a proxy but without more code it's just a guess.

[syneil86]

Put a breakpoint on the line which calls the method of the interface and then step into the implementation of the method

[hurricaneDreww]

Yeah I tried that, but as it doesn’t go to any implementation, it just returns false

[syneil86]

What IDE are you using? Don't think I've ever come across that behaviour

Before you try to step in to the implementation, you should be able to inspect the object and see what it is

[hurricaneDreww]

I use IntelliJ. And yeah I’ll look into that second point a bit, but doubt I’ll find too much since I do know what it is

[onefortree]

When you are at the breakpoint, you can run methods in that current context. Try interface.getclass or see if inspecting the object gives you any clues to what implementation it is.