使用Java Reflection调用带有ActionEvent参数的方法的最干净方法是什么？

Question

Here is a very simplified example of what I am trying to accomplish. I am maintaining code that was written a long time ago by someone else and do not have the ability to change it.

import java.awt.event.ActionEvent;
import java.lang.reflect.Method;




public class Main {
      public static void main(String[] args) throws Exception {

            Class cls = Class.forName("Main");
            Main obj = (Main) cls.newInstance();

            Method m = cls.getDeclaredMethod("test", ActionEvent.class);

            m.invoke(obj, null); <--- throws an IllegalArgumentException
       }

       public void test(ActionEvent x) {
          System.out.println("Yeah");
       }
}

The above code throws java.lang.IllegalArgumentException: wrong number of arguments . I know I could pass new ActionEvent(new Object(), 0, null) as a parameter, but I am not sure this is the best/cleanest way to accomplish this. Note, the method test doesn't actually use the ActionEvent parameter.

Answer 1

The problem here is that the null in

m.invoke(obj, null);

is inferred as an argument of type Object[] which represents the collection of arguments to be passed to the method being invoked.

Instead, cast the null to Object if your intention was to simulate the following invocation

obj.test(null);

That is equivalent to

m.invoke(obj, (Object) null);

Answer 2

Well, you will have to call the method with the right parameter in one way or the other.

Note however, that some time ago, I've written a reflective action .

try {  
    Action test = new ReflectiveXAction(this, "test");  
} catch (NoSuchMethodException ex) {  
    ex.printStackTrace();  
}  

...

test.actionPerformed(new ActionEvent(this, ActionEvent.ACTION_PERFORMED, "someId"));

or

test.actionPerformed(null);

Usually, the actionPerformed method gets called by a component such JButton, however.

Maybe you find it useful. The library is Open Source.

Tutorial: http://www.softsmithy.org/lib/current/docs/tutorial/swing/action/index.html#reflective

You can get the library either directly from Maven Central:

<dependency>
    <groupId>org.softsmithy.lib</groupId>
    <artifactId>softsmithy-lib-swing</artifactId>
    <version>0.5</version>
</dependency>

or you can download it from here: http://sourceforge.net/projects/softsmithy/files/softsmithy/v0.5/

If you're using Java SE 8 (recommended) you could also consider to use lambdas/ method references, eg (untested):

ActionListener test = this::test;