Question

I have an interface and there are couple of implementations for that Interface. Now I need to invoke the correct Implemented method dynamically.

I get the Implementation Class name from a property file. Now I have to invoke the method using reflection.

Could you please suggest the best approach to do it?

//This is my Interface.

public interface ITestInterface{
    public CustomVO customMethod(CustomObj1 obj1,CustomObjec2 obj2);
}

//This class implements the above interface

public class TestInterface implements ITestInterface{
   public CustomVO customMethod(CustomObj1 obj1,CustomObjec2 obj2){

   //some logic
  }
}

Now I need to invoke customMethod(obj1,obj2) using Reflection. I’ve the class name of TestInterface.

This is what I did.
I created an instance of TestInterface using Class.forName(className).newInstance();

Class[] paramTypes = new Class[ 2 ];
paramTypes [ 0 ] = CustomObj1.class;
paramTypes [ 1 ] = CustomObj2.class;
Object obj=Class.forName(className).newInstance();

Class.forName(className).getMethod( "customMethod", paramTypes ).invoke( obj, obj1,obj2);

I do not know if this is the correct way to do this? Could you please guide me?

Answer 1

Creating the object via reflection is fine as you did it (barring error handling, which I assume you omitted here for brevity).

But once you have the object created, why not simply downcast it to ITestInterface and call its method(s) directly?

ITestInterface obj = (ITestInterface) Class.forName(className).newInstance();
obj.customMethod(param1, param2);

(again, handling ClassCastException is omitted here, but it should be dealt with in production code.)