java – 如何弃用内部接口

我需要在Java SDK中弃用API以使它们更通用.但我无法弄清楚如何做以下情况:

public class AdoptDog {
    public interface OnDogAdoption {
        public void onDogAdoption(String dogName);
    }
    public void adoptDog(final String dogName, OnDogAdoption callbackObj) {
        // Perform asynchronous tasks...
            // Then call the callback:
            callbackObj.onDogAdoption(dogName);
    }
}

SDK的用户进行如下调用:

AdoptDog adoptDog = new AdoptDog();
adoptDog.adoptDog("Snowball", new OnDogAdoption {
    @Override
    public void onDogAdoption(String dogName) {
        System.out.println("Welcome " + dogName);
    }
};

我想概括从Dog到Pet,并弃用提到Dog的API.为了向后兼容,我在弃用API时不必更改上面采用Snowball的代码片段.

我是如何尝试弃用Dog API的:

// Introduce Pet API

public class AdoptPet {
    public interface OnPetAdoption {
        public void onPetAdoption(String petName);
    }
    public void adoptPet(final String petName, OnPetAdoption callbackObj) {
        // Perform asynchronous tasks...
            // Then call the callback:
            if (callbackObj instanceof OnDogAdoption) {
                ((OnDogAdoption) callbackObj).onDogAdoption(petName);
            }
            else {
                callbackObj.onPetAdoption(petName);
            }
    }
}

// Dog API now extends Pet API for backward compatibility

@Deprecated
public class AdoptDog extends AdoptPet {
    @Deprecated
    public interface OnDogAdoption extends AdoptPet.OnPetAdoption {
        @Deprecated
        public void onDogAdoption(String dogName);
    }
    @Deprecated
    public void adoptDog(final String dogName, OnDogAdoption callbackObj) {
        super.adoptPet(dogName, callbackObj);
    }
}

问题是它不完全向后兼容. SDK的用户必须实现AdoptPet.OnPetAdoption.onPetAdoption(),否则他们会收到编译器错误:

AdoptDog adoptDog = new AdoptDog();
adoptDog.adoptDog("Snowball", new OnDogAdoption {
    @Override
    public void onDogAdoption(String dogName) {
        System.out.println("Welcome " + dogName);
    }

    // PROBLEM: How avoid customers having to implement this dummy method? 
    @Override
    public void onPetAdoption(String petName) {
        assert("This code should not be reached");
    }
};

是否有其他方法可以弃用AdoptDog(特别是OnDogAdoption)并保持完全向后兼容性?

解决方法:

您没有扩展OnPetAdoption. OnDogAdoption不是OnPetAdoption. OnPetAdoption也可以处理猫的采用. OnDogAdoption不能.

我建议您将OnDogAdoption包装在OnDogAdoptionDispatcher中,并使用该调度程序调用new方法,例如:

@Deprecated
public class AdoptDog extends AdoptPet {
    @Deprecated
    public interface OnDogAdoption {
        @Deprecated
        public void onDogAdoption(String dogName);
    }

    private static class DogAdoptionDispatcher implements AdoptPet.OnPetAdoption {
            final OnDogAdoption target;
            public DogAdoptionDispatcher(OnDogAdoption target) {
                this.target = target;
            }
            @Override
            public void onPetAdoption(String petName) {
                target.onDogAdoption(petName);
            }
    }

    @Deprecated
    public void adoptDog(final String dogName, OnDogAdoption callbackObj) {
        super.adoptPet(dogName, new DogAdoptionDispatcher(callbackObj));
    }
}

这样,您仍然具有向后兼容性和干净的新界面.

如果您使用的是Java 8或更高版本,则不需要单独的类,您可以这样做

public void adoptDog(final String dogName, OnDogAdoption callbackObj) {
    super.adoptPet(dogName, callbackObj::onDogAdoption);
}
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