Java AWT/Swing getComponentVariableName(component)

Sometimes you have a component that you know almost nothing about, and it'd be nice to get the name of it, somehow, but since I haven't taken the time to explicitly name every one of my components, I tried something else. Here's how to use it ...

    private void genericErrorHandler(java.awt.event.AWTEvent evt) {

        String componentName = Awt2.getComponentVariableName(evt.getSource());
        System.out.println(componentName);

    }

Here's the code to make the above code work...

import java.awt.Component;
import java.lang.reflect.Field;

/**
 * additional utilities for working with AWT/Swing.
 * this is a single method for demo purposes.
 * recommended to be combined into a single class
 * module with other similar methods,
 * e.g. MySwingUtilities
 *
 * @author http://javajon.blogspot.com/2013/07/java-awtswing-getcomponentvariablenamec.html
 */
public class Awt2 {

    /**
     * substitute for component.getName() when used in NetBeans or other IDE
     * that creates class fields to hold the components. uses reflection to
     * search through class fields for a match.
     * @param component the component to look for
     * @return hopefully the variable name used to hold this component
     */
    static public String getComponentVariableName(Object object) {

        if (object instanceof Component) {
            final Component component = (Component) object;
            final StringBuilder sb = new StringBuilder();

            // find the form where the variable name would be likely to exist
            final Component parentForm = getParentForm(component);

            // loop through all of the class fields on that form
            for (Field field : parentForm.getClass().getDeclaredFields()) {

                try {
                    // let us look at private fields, please
                    field.setAccessible(true);

                    // get a potential match
                    final Object potentialMatch = field.get(parentForm);

                    // compare it
                    if (potentialMatch == component) {

                        // return the name of the variable used
                        // to hold this component
                        if (sb.length() > 0) sb.append(",");
                        sb.append(field.getName());
                    }

                } catch (SecurityException | IllegalArgumentException 
                        | IllegalAccessException ex) {

                    // ignore exceptions
                }
            }

            if (sb.length() > 0) {
                return sb.toString();
            }
        }

        // if we get here, we're probably trying to find the form
        // itself, in which case it may be more useful to print
        // the class name (MyJFrame) than the AWT-assigned name
        // of the form (frame0)
        final String className = object.getClass().getName();
        final String[] split = className.split("\\.");
        final int lastIndex = split.length - 1;
        return (lastIndex >= 0) ? split[lastIndex] : className;

    }

    /**
     * traverses up the component tree to find the top, which i assume is the
     * dialog or frame upon which this component lives.
     * @param sourceComponent
     * @return top level parent component
     */
    static public Component getParentForm(Component sourceComponent) {
        while (sourceComponent.getParent() != null) {
            sourceComponent = sourceComponent.getParent();
        }
        return sourceComponent;
    }
}

Using the above code, here's an example of a global AWT/Swing event catcher that just dumps everything to the system console...

    Toolkit.getDefaultToolkit().addAWTEventListener(new AWTEventListener() {

        @Override
        public void eventDispatched(AWTEvent event) {
            System.out.print(Awt2.getComponentVariableName(event.getSource()));
            System.out.print(": ");
            System.out.print(event.paramString());
            System.out.println();
        }
    }, -1L);

Java AWT/Swing getComponentByName(window, name)

C# offers a Controls collection, so you can access controls by name using form.Controls["controlName"]. Java/Swing does not appear to have any such functionality, but here's what I'd like to be able to do ...

    // get a button (or other component) by name
    JButton button = Awt1.getComponentByName(someOtherFrame, "jButton1");

    // do something useful with it (like toggle it's enabled state)
    button.setEnabled(!button.isEnabled());

So, you know ... here's the code to make it possible ...

import java.awt.Component;
import java.awt.Window;
import java.lang.reflect.Field;

/**
 * additional utilities for working with AWT/Swing.
 * this is a single method for demo purposes.
 * recommended to be combined into a single class
 * module with other similar methods,
 * e.g. MySwingUtilities
 * 
 * @author http://javajon.blogspot.com/2013/07/java-awtswing-getcomponentbynamewindow.html
 */
public class Awt1 {

    /**
     * attempts to retrieve a component from a JFrame or JDialog using the name
     * of the private variable that NetBeans (or other IDE) created to refer to
     * it in code.
     * @param <T> Generics allow easier casting from the calling side.
     * @param window JFrame or JDialog containing component
     * @param name name of the private field variable, case sensitive
     * @return null if no match, otherwise a component.
     */
    @SuppressWarnings("unchecked")
    static public <T extends Component> T getComponentByName(Window window, String name) {

        // loop through all of the class fields on that form
        for (Field field : window.getClass().getDeclaredFields()) {

            try {
                // let us look at private fields, please
                field.setAccessible(true);

                // compare the variable name to the name passed in
                if (name.equals(field.getName())) {

                    // get a potential match (assuming correct <T>ype)
                    final Object potentialMatch = field.get(window);

                    // cast and return the component
                    return (T) potentialMatch;
                }

            } catch (SecurityException | IllegalArgumentException 
                    | IllegalAccessException ex) {

                // ignore exceptions
            }

        }

        // no match found
        return null;
    }

}

Calling Overridable Methods from the Constructor

NetBeans will warn you not to call an overridable method from your constructor, and for good reason ...

public class PlayerCharacter implements DailyCycle {

    private static final int MAX_MOVES_REMAINING = 10;
    private static final int NEW_MOVES_PER_DAY = 3;

    private int movesRemaining;

    public PlayerCharacter() {
        newDay(); // WARNING
    }

    @Override
    public void newDay() {
        movesRemaining += NEW_MOVES_PER_DAY;
        if (movesRemaining > MAX_MOVES_REMAINING) {
            movesRemaining = MAX_MOVES_REMAINING;
        }
    }

}

What I Do...

I'm not really sure how other people handle this, but like to make a local version of the method (CTRL-SHIFT-M in NetBeans)...

 

public class PlayerCharacter implements DailyCycle {

    private static final int MAX_MOVES_REMAINING = 10;
    private static final int NEW_MOVES_PER_DAY = 3;

    private int movesRemaining;

    public PlayerCharacter() {
        newDayLocal();
    }

    @Override
    public void newDay() {
        newDayLocal();
    }

    private void newDayLocal() {
        movesRemaining += NEW_MOVES_PER_DAY;
        if (movesRemaining > MAX_MOVES_REMAINING) {
            movesRemaining = MAX_MOVES_REMAINING;
        }
    }

}

This not only solves the warning, but actually solves the problem. The object is no longer allowing subclasses to inject out-of-sequence code into the constructor by overriding a method.

 How do other people handle this? Is there a standard pattern?