java中的回调行为

Question

My question is more towards the design pattern to use for my implementation. I have the code written as follows -

X-Service.java

handler.setListeners(new HttpResponseHandler.conListers() {

    @Override
    public void success() {

    }

}); 

HttpResponseHandler

protected conListers conListener;
public interface conListers {
    public void success();
}

public void conListers(conListers listener) {
    this.conListers = listener;
}

So now my problem is I can use this technique If I had just one type of success function. To be more clear I have multiple services where success method have different signature like --

public void success(String x);
public void success(HashMap y, Integer z);

I do not want to put all the methods in the interface, as I will have to implement them in all the services. I need a way in which I can just implement the success method I want.

Answer 1

You could define the interface using a generic type declaration:

public interface conListers<E> {
    public void success(E value);
}

Alternatively, if you need a variable number of arguments of the same type then you can use:

public interface conListers<E> {
    public void success(E... value);
}

If you need a fixed number of arguments then you can just test the length of the value argument in the definition of success() in the implementing class.

However, I can't think of any pattern you can use to allow success() to take a variably fixed number of different typed arguments unless you use Object but that then brings its own issues (like having to type check all the arguments within the implementing class):

public interface conListers {
    public void success(Object... value);
}

Answer 2

You can use the command pattern in this scenario, basically the conListener will be your command. You'll have as many conListeners implementations as your services.

Example:

public class conListenersA implements conListener{
    protected Service serviceA;
    public void success(){
        serviceA.success(arg1);//the method has  arguments
    }
}

public class conListenersB implements conListener{
    protected Service serviceB;
    public void success(){
        serviceB.success(arg1,arg2);//the method has 2 arguments
    }
}

The advantage is that whenever you need to execute a conListener you call will be "uniform", as simple as conListener.success()

Answer 3

You can try with most general Java class Object as a parameter and use varargs:

public interface conListers {
    public void success(Object... arguments);
}

Inside implementation you'll have to figure out object types and the number of arguments, but you'll have a clean interface for your functions.

Another approach is to define a class that holds all of your arguments that you are planning to send on a success, and then inside implemented success methods get parameters that you really need.