How to pass an object to a method using reflection in java

Question

I am working on some code which takes a string input dynamically, so i chose reflection as i didnt find any other better approach for it,

My current code:

Class xyzClass = Class.forName("com.example.Xyz");

Object abcObj =  abcService.generateAbcObj("some string input");
Method method = xyzClass.getDeclaredMethod("add", abcObj); // i want to pass this abcObj to this declared method add but getDeclaredMethod takes class as a parameter

Can anybody suggest way to do in reflection as i want it in a dynamic way or any other way to achieve it in a better sense?

Answer 1

Just pass the class (because you first has to identify the method you want to call, and then call it, and without the class of the parameters, you could get a method overloading that is not the one you want):

Method method = xyzClass.getDeclaredMethod("add", abcObj.getClass());

and then you can invoke it:

method.invoke(/*instance of com.example.Xyz on which you want to call add*/, abcObj);

Answer 2

To allow a method to modify an argument, you must pass in an object. Objects in Java are also passed by value, however, the value of an object is a reference. So, the effect is that the object is passed in by reference. ( For more info )

With reflection where you are passing the object to the method, you should use Method.invoke . As you've got a single parameter do this:

method.invoke(this, abcObj);