Reflection, menus, and ActionListeners

Question

Hi everybody,
I was doing some reading in the Java APIs and came across reflection, and it seemed like a good idea for some menus I'm implementing, but I'm not fully sure, so I'd like some advice, please, if anyone would be willing.
I have a lot of menus on a menu bar, and each menu item on the bar pops up a different kind of window (each window is distinct and has its own constructor; they're all encapsulated objects). My original idea was to add actionListeners to each menu item like so:
for each item:
item.addActionListener( new ActionListener() {
public void actionPerformed( ActionEvent e ) {
// the constructor for a particular window
});The issue with that approach, as I've learned, is that this repetitive call, while it works, bloats my classes, makes them almost impossible to read, and involves a lot of cutting and pasting so it's prone to mistakes.
So...then I stumbled on reflection. From reading the API, it appears (please correct me if I'm wrong) that you can get particular methods and constructors from classes using reflection, and then call them. This would allow me to make two small overloaded methods, to cut down on the amount of code, like so:
public JMenuItem addConstructorAction( JMenuItem item, Constructor c ) {
item.addActionListener( new ActionListener() {
public void actionPerformed( ActionEvent e ) {
c.newInstance();
return item;
public JMenuItem addConstructorAction( JMenuItem item, Method m ) {
item.addActionListener( new ActionListener() {
public void actionPerformed( ActionEvent e ) {
m.invoke( params );
return item;
}So, am I right that this is how reflection works, or have I misread something? If anyone could give me advice on how to use this properly or an alternate idea, I'd appreciate it.
Thanks,
Jezzica85
PS -- Sorry about the indenting on the code examples; I don't know why they didn't indent, hopefully they're still readable.
Edited by: jezzica85 on Jan 14, 2009 7:04 AM

Answer 1

Well, I didn't think this would turn into a SSCCE situation, but that's OK-- I probably should have assumed that to begin with. Anyway, here's a small program that shows what I'm talking about:
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
public class MenuTest {
     public static void main(String[] args) {
          try {
               JFrame frame = new JFrame();
               frame.setSize( 300, 300 );
               frame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
               JMenuBar test = new JMenuBar();
               JMenu menu = new JMenu( "myTest" );
               JMenuItem item = new JMenuItem( "TestWindow test" );
               item.addActionListener( new ActionListener() {
                    public void actionPerformed( ActionEvent ex ) {
                         new TestWindow( "TestWindow" );
               menu.add( item );
               JMenuItem item2 = new JMenuItem( "TestWindow2 test" );
               item2.addActionListener( new ActionListener() {
                    public void actionPerformed( ActionEvent ex ) {
                         new TestWindow2( "TestWindow2" );
               menu.add( item2 );
               test.add( menu );
               frame.setJMenuBar( test );
               frame.setVisible( true );
          } catch( Exception e ) {
               e.printStackTrace();
               System.exit( -1 );
class TestWindow extends JDialog {
     public TestWindow( String title ) {
          setTitle( title );
          setSize( 300, 300 );
          setDefaultCloseOperation( JDialog.DISPOSE_ON_CLOSE );
          setVisible( true );
class TestWindow2 extends JDialog {
     public TestWindow2( String title ) {
          setTitle( title );
          add( new JLabel( "blah" ) );
          setSize( 300, 300 );
          setDefaultCloseOperation( JDialog.DISPOSE_ON_CLOSE );
          setVisible( true );
}Basically, each menu item calls up a different kind of window (these are very simplified obviously). In my real application I have more than 40 different windows (because the application needs to do a lot), so repeating the actionListener code can get tedious. It doesn't look like much here, but 9 lines of code (including whitespace for readability) times at least 40 menu items is more than 350 lines of code for menu items alone. That's what I'm trying to avoid.
Thanks,
Jezzica85