https://openjdk.java.net/ 
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
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 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */
package java.beans;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Proxy;
import java.lang.reflect.Method;
import java.security.AccessControlContext;
import java.security.AccessController;
import java.security.PrivilegedAction;

import sun.reflect.misc.MethodUtil;
import sun.reflect.misc.ReflectUtil;


The EventHandler class provides support for dynamically generating event listeners whose methods execute a simple statement involving an incoming event object and a target object. 
 The EventHandler class is intended to be used by interactive tools, such as application builders, that allow developers to make connections between beans. Typically connections are made from a user interface bean (the event source)
to an application logic bean (the target). The most effective connections of this kind isolate the application logic from the user interface. For example, the EventHandler for a connection from a JCheckBox to a method that accepts a boolean value can deal with extracting the state of the check box and passing it directly to the method so that the method is isolated from the user interface layer. 
 Inner classes are another, more general way to handle events from user interfaces. The EventHandler class handles only a subset of what is possible using inner classes. However, EventHandler works better with the long-term persistence scheme than inner classes. Also, using EventHandler in large applications in which the same interface is implemented many times can reduce the disk and memory footprint of the application. 
 The reason that listeners created with EventHandler have such a small footprint is that the Proxy class, on which the EventHandler relies, shares implementations of identical interfaces. For example, if you use the EventHandler create methods to make all the ActionListeners in an application, all the action listeners will be instances of a single class (one created by the Proxy class). In general, listeners based on the Proxy class require one listener class to be created per listener type (interface),
whereas the inner class
approach requires one class to be created per listener
(object that implements the interface).

 You don't generally deal directly with EventHandler instances. Instead, you use one of the EventHandler create methods to create an object that implements a given listener interface. This listener object uses an EventHandler object behind the scenes to encapsulate information about the event, the object to be sent a message when the event occurs, the message (method) to be sent, and any argument to the method. The following section gives examples of how to create listener objects using the create methods. 
Examples of Using EventHandler
 The simplest use of EventHandler is to install a listener that calls a method on the target object with no arguments. In the following example we create an ActionListener that invokes the toFront method on an instance of javax.swing.JFrame. 


myButton.addActionListener(
   (ActionListener)EventHandler.create(ActionListener.class, frame, "toFront"));



 When myButton is pressed, the statement frame.toFront() will be executed. One could get the same effect, with some additional compile-time type safety, by defining a new implementation of the ActionListener interface and adding an instance of it to the button: 


//Equivalent code using an inner class instead of EventHandler.
myButton.addActionListener(new ActionListener() {
   public void actionPerformed(ActionEvent e) {
       frame.toFront();
   }
});



 The next simplest use of EventHandler is to extract a property value from the first argument of the method in the listener interface (typically an event object) and use it to set the value of a property in the target object. In the following example we create an ActionListener that sets the nextFocusableComponent property of the target (myButton) object to the value of the "source" property of the event. 


EventHandler.create(ActionListener.class, myButton, "nextFocusableComponent", "source")




This would correspond to the following inner class implementation:



//Equivalent code using an inner class instead of EventHandler.
new ActionListener() {
   public void actionPerformed(ActionEvent e) {
       myButton.setNextFocusableComponent((Component)e.getSource());
   }
}



 It's also possible to create an EventHandler that just passes the incoming event object to the target's action. If the fourth EventHandler.create argument is an empty string, then the event is just passed along: 


EventHandler.create(ActionListener.class, target, "doActionEvent", "")




This would correspond to the following inner class implementation:



//Equivalent code using an inner class instead of EventHandler.
new ActionListener() {
   public void actionPerformed(ActionEvent e) {
       target.doActionEvent(e);
   }
}



 Probably the most common use of EventHandler is to extract a property value from the source of the event object and set this value as the value of a property of the target object. In the following example we create an ActionListener that sets the "label" property of the target object to the value of the "text" property of the source (the value of the "source" property) of the event. 


EventHandler.create(ActionListener.class, myButton, "label", "source.text")




This would correspond to the following inner class implementation:



//Equivalent code using an inner class instead of EventHandler.
new ActionListener {
   public void actionPerformed(ActionEvent e) {
       myButton.setLabel(((JTextField)e.getSource()).getText());
   }
}




The event property may be "qualified" with an arbitrary number
of property prefixes delimited with the "." character. The "qualifying"
names that appear before the "." characters are taken as the names of
properties that should be applied, left-most first, to
the event object.


For example, the following action listener



EventHandler.create(ActionListener.class, target, "a", "b.c.d")




might be written as the following inner class
(assuming all the properties had canonical getter methods and
returned the appropriate types):



//Equivalent code using an inner class instead of EventHandler.
new ActionListener {
   public void actionPerformed(ActionEvent e) {
       target.setA(e.getB().getC().isD());
   }
}




The target property may also be "qualified" with an arbitrary number
of property prefixs delimited with the "." character.  For example, the
following action listener:

  EventHandler.create(ActionListener.class, target, "a.b", "c.d")


might be written as the following inner class
(assuming all the properties had canonical getter methods and
returned the appropriate types):

  //Equivalent code using an inner class instead of EventHandler.
  new ActionListener {
    public void actionPerformed(ActionEvent e) {
        target.getA().setB(e.getC().isD());
   }
}



 As EventHandler ultimately relies on reflection to invoke a method we recommend against targeting an overloaded method. For example, if the target is an instance of the class MyTarget which is defined as: 
  public class MyTarget {
    public void doIt(String);
    public void doIt(Object);
  }

 Then the method doIt is overloaded. EventHandler will invoke the method that is appropriate based on the source. If the source is null, then either method is appropriate and the one that is invoked is undefined. For that reason we recommend against targeting overloaded methods. 
Author:Mark Davidson, Philip Milne, Hans Muller
See Also:
Since:1.4
/**
 * The {@code EventHandler} class provides
 * support for dynamically generating event listeners whose methods
 * execute a simple statement involving an incoming event object
 * and a target object.
 * <p>
 * The {@code EventHandler} class is intended to be used by interactive tools, such as
 * application builders, that allow developers to make connections between
 * beans. Typically connections are made from a user interface bean
 * (the event <em>source</em>)
 * to an application logic bean (the <em>target</em>). The most effective
 * connections of this kind isolate the application logic from the user
 * interface.  For example, the {@code EventHandler} for a
 * connection from a {@code JCheckBox} to a method
 * that accepts a boolean value can deal with extracting the state
 * of the check box and passing it directly to the method so that
 * the method is isolated from the user interface layer.
 * <p>
 * Inner classes are another, more general way to handle events from
 * user interfaces.  The {@code EventHandler} class
 * handles only a subset of what is possible using inner
 * classes. However, {@code EventHandler} works better
 * with the long-term persistence scheme than inner classes.
 * Also, using {@code EventHandler} in large applications in
 * which the same interface is implemented many times can
 * reduce the disk and memory footprint of the application.
 * <p>
 * The reason that listeners created with {@code EventHandler}
 * have such a small
 * footprint is that the {@code Proxy} class, on which
 * the {@code EventHandler} relies, shares implementations
 * of identical
 * interfaces. For example, if you use
 * the {@code EventHandler create} methods to make
 * all the {@code ActionListener}s in an application,
 * all the action listeners will be instances of a single class
 * (one created by the {@code Proxy} class).
 * In general, listeners based on
 * the {@code Proxy} class require one listener class
 * to be created per <em>listener type</em> (interface),
 * whereas the inner class
 * approach requires one class to be created per <em>listener</em>
 * (object that implements the interface).
 *
 * <p>
 * You don't generally deal directly with {@code EventHandler}
 * instances.
 * Instead, you use one of the {@code EventHandler}
 * {@code create} methods to create
 * an object that implements a given listener interface.
 * This listener object uses an {@code EventHandler} object
 * behind the scenes to encapsulate information about the
 * event, the object to be sent a message when the event occurs,
 * the message (method) to be sent, and any argument
 * to the method.
 * The following section gives examples of how to create listener
 * objects using the {@code create} methods.
 *
 * <h2>Examples of Using EventHandler</h2>
 *
 * The simplest use of {@code EventHandler} is to install
 * a listener that calls a method on the target object with no arguments.
 * In the following example we create an {@code ActionListener}
 * that invokes the {@code toFront} method on an instance
 * of {@code javax.swing.JFrame}.
 *
 * <blockquote>
 *<pre>
 *myButton.addActionListener(
 *    (ActionListener)EventHandler.create(ActionListener.class, frame, "toFront"));
 *</pre>
 * </blockquote>
 *
 * When {@code myButton} is pressed, the statement
 * {@code frame.toFront()} will be executed.  One could get
 * the same effect, with some additional compile-time type safety,
 * by defining a new implementation of the {@code ActionListener}
 * interface and adding an instance of it to the button:
 *
 * <blockquote>
 *<pre>
//Equivalent code using an inner class instead of EventHandler.
 *myButton.addActionListener(new ActionListener() {
 *    public void actionPerformed(ActionEvent e) {
 *        frame.toFront();
 *    }
 *});
 *</pre>
 * </blockquote>
 *
 * The next simplest use of {@code EventHandler} is
 * to extract a property value from the first argument
 * of the method in the listener interface (typically an event object)
 * and use it to set the value of a property in the target object.
 * In the following example we create an {@code ActionListener} that
 * sets the {@code nextFocusableComponent} property of the target
 * (myButton) object to the value of the "source" property of the event.
 *
 * <blockquote>
 *<pre>
 *EventHandler.create(ActionListener.class, myButton, "nextFocusableComponent", "source")
 *</pre>
 * </blockquote>
 *
 * This would correspond to the following inner class implementation:
 *
 * <blockquote>
 *<pre>
//Equivalent code using an inner class instead of EventHandler.
 *new ActionListener() {
 *    public void actionPerformed(ActionEvent e) {
 *        myButton.setNextFocusableComponent((Component)e.getSource());
 *    }
 *}
 *</pre>
 * </blockquote>
 *
 * It's also possible to create an {@code EventHandler} that
 * just passes the incoming event object to the target's action.
 * If the fourth {@code EventHandler.create} argument is
 * an empty string, then the event is just passed along:
 *
 * <blockquote>
 *<pre>
 *EventHandler.create(ActionListener.class, target, "doActionEvent", "")
 *</pre>
 * </blockquote>
 *
 * This would correspond to the following inner class implementation:
 *
 * <blockquote>
 *<pre>
//Equivalent code using an inner class instead of EventHandler.
 *new ActionListener() {
 *    public void actionPerformed(ActionEvent e) {
 *        target.doActionEvent(e);
 *    }
 *}
 *</pre>
 * </blockquote>
 *
 * Probably the most common use of {@code EventHandler}
 * is to extract a property value from the
 * <em>source</em> of the event object and set this value as
 * the value of a property of the target object.
 * In the following example we create an {@code ActionListener} that
 * sets the "label" property of the target
 * object to the value of the "text" property of the
 * source (the value of the "source" property) of the event.
 *
 * <blockquote>
 *<pre>
 *EventHandler.create(ActionListener.class, myButton, "label", "source.text")
 *</pre>
 * </blockquote>
 *
 * This would correspond to the following inner class implementation:
 *
 * <blockquote>
 *<pre>
//Equivalent code using an inner class instead of EventHandler.
 *new ActionListener {
 *    public void actionPerformed(ActionEvent e) {
 *        myButton.setLabel(((JTextField)e.getSource()).getText());
 *    }
 *}
 *</pre>
 * </blockquote>
 *
 * The event property may be "qualified" with an arbitrary number
 * of property prefixes delimited with the "." character. The "qualifying"
 * names that appear before the "." characters are taken as the names of
 * properties that should be applied, left-most first, to
 * the event object.
 * <p>
 * For example, the following action listener
 *
 * <blockquote>
 *<pre>
 *EventHandler.create(ActionListener.class, target, "a", "b.c.d")
 *</pre>
 * </blockquote>
 *
 * might be written as the following inner class
 * (assuming all the properties had canonical getter methods and
 * returned the appropriate types):
 *
 * <blockquote>
 *<pre>
//Equivalent code using an inner class instead of EventHandler.
 *new ActionListener {
 *    public void actionPerformed(ActionEvent e) {
 *        target.setA(e.getB().getC().isD());
 *    }
 *}
 *</pre>
 * </blockquote>
 * The target property may also be "qualified" with an arbitrary number
 * of property prefixs delimited with the "." character.  For example, the
 * following action listener:
 * <pre>
 *   EventHandler.create(ActionListener.class, target, "a.b", "c.d")
 * </pre>
 * might be written as the following inner class
 * (assuming all the properties had canonical getter methods and
 * returned the appropriate types):
 * <pre>
 *   //Equivalent code using an inner class instead of EventHandler.
 *   new ActionListener {
 *     public void actionPerformed(ActionEvent e) {
 *         target.getA().setB(e.getC().isD());
 *    }
 *}
 *</pre>
 * <p>
 * As {@code EventHandler} ultimately relies on reflection to invoke
 * a method we recommend against targeting an overloaded method.  For example,
 * if the target is an instance of the class {@code MyTarget} which is
 * defined as:
 * <pre>
 *   public class MyTarget {
 *     public void doIt(String);
 *     public void doIt(Object);
 *   }
 * </pre>
 * Then the method {@code doIt} is overloaded.  EventHandler will invoke
 * the method that is appropriate based on the source.  If the source is
 * null, then either method is appropriate and the one that is invoked is
 * undefined.  For that reason we recommend against targeting overloaded
 * methods.
 *
 * @see java.lang.reflect.Proxy
 * @see java.util.EventObject
 *
 * @since 1.4
 *
 * @author Mark Davidson
 * @author Philip Milne
 * @author Hans Muller
 *
 */
public class EventHandler implements InvocationHandler {
    private Object target;
    private String action;
    private final String eventPropertyName;
    private final String listenerMethodName;
    private final AccessControlContext acc = AccessController.getContext();

    
Creates a new EventHandler object; you generally use one of the create methods instead of invoking this constructor directly. Refer to 
the general version of create for a complete description of the eventPropertyName and listenerMethodName parameter. 
Params:
  • target – the object that will perform the action
  • action – the name of a (possibly qualified) property or method on
       the target
  • eventPropertyName – the (possibly qualified) name of a readable property of the incoming event
  • listenerMethodName – the name of the method in the listener interface that should trigger the action
Throws:
See Also:
/**
     * Creates a new {@code EventHandler} object;
     * you generally use one of the {@code create} methods
     * instead of invoking this constructor directly.  Refer to
     * {@link java.beans.EventHandler#create(Class, Object, String, String)
     * the general version of create} for a complete description of
     * the {@code eventPropertyName} and {@code listenerMethodName}
     * parameter.
     *
     * @param target the object that will perform the action
     * @param action the name of a (possibly qualified) property or method on
     *        the target
     * @param eventPropertyName the (possibly qualified) name of a readable property of the incoming event
     * @param listenerMethodName the name of the method in the listener interface that should trigger the action
     *
     * @throws NullPointerException if {@code target} is null
     * @throws NullPointerException if {@code action} is null
     *
     * @see EventHandler
     * @see #create(Class, Object, String, String, String)
     * @see #getTarget
     * @see #getAction
     * @see #getEventPropertyName
     * @see #getListenerMethodName
     */
    @ConstructorProperties({"target", "action", "eventPropertyName", "listenerMethodName"})
    public EventHandler(Object target, String action, String eventPropertyName, String listenerMethodName) {
        this.target = target;
        this.action = action;
        if (target == null) {
            throw new NullPointerException("target must be non-null");
        }
        if (action == null) {
            throw new NullPointerException("action must be non-null");
        }
        this.eventPropertyName = eventPropertyName;
        this.listenerMethodName = listenerMethodName;
    }

    
Returns the object to which this event handler will send a message.

See Also:
Returns:the target of this event handler
/**
     * Returns the object to which this event handler will send a message.
     *
     * @return the target of this event handler
     * @see #EventHandler(Object, String, String, String)
     */
    public Object getTarget()  {
        return target;
    }

    
Returns the name of the target's writable property
that this event handler will set,
or the name of the method that this event handler
will invoke on the target.

See Also:
Returns:the action of this event handler
/**
     * Returns the name of the target's writable property
     * that this event handler will set,
     * or the name of the method that this event handler
     * will invoke on the target.
     *
     * @return the action of this event handler
     * @see #EventHandler(Object, String, String, String)
     */
    public String getAction()  {
        return action;
    }

    
Returns the property of the event that should be
used in the action applied to the target.

See Also:
Returns:the property of the event
/**
     * Returns the property of the event that should be
     * used in the action applied to the target.
     *
     * @return the property of the event
     *
     * @see #EventHandler(Object, String, String, String)
     */
    public String getEventPropertyName()  {
        return eventPropertyName;
    }

    
Returns the name of the method that will trigger the action. A return value of null signifies that all methods in the listener interface trigger the action. 
See Also:
Returns:the name of the method that will trigger the action
/**
     * Returns the name of the method that will trigger the action.
     * A return value of {@code null} signifies that all methods in the
     * listener interface trigger the action.
     *
     * @return the name of the method that will trigger the action
     *
     * @see #EventHandler(Object, String, String, String)
     */
    public String getListenerMethodName()  {
        return listenerMethodName;
    }

    private Object applyGetters(Object target, String getters) {
        if (getters == null || getters.equals("")) {
            return target;
        }
        int firstDot = getters.indexOf('.');
        if (firstDot == -1) {
            firstDot = getters.length();
        }
        String first = getters.substring(0, firstDot);
        String rest = getters.substring(Math.min(firstDot + 1, getters.length()));

        try {
            Method getter = null;
            if (target != null) {
                getter = Statement.getMethod(target.getClass(),
                                      "get" + NameGenerator.capitalize(first),
                                      new Class<?>[]{});
                if (getter == null) {
                    getter = Statement.getMethod(target.getClass(),
                                   "is" + NameGenerator.capitalize(first),
                                   new Class<?>[]{});
                }
                if (getter == null) {
                    getter = Statement.getMethod(target.getClass(), first, new Class<?>[]{});
                }
            }
            if (getter == null) {
                throw new RuntimeException("No method called: " + first +
                                           " defined on " + target);
            }
            Object newTarget = MethodUtil.invoke(getter, target, new Object[]{});
            return applyGetters(newTarget, rest);
        }
        catch (Exception e) {
            throw new RuntimeException("Failed to call method: " + first +
                                       " on " + target, e);
        }
    }

    
Extract the appropriate property value from the event and pass it to the action associated with this EventHandler. 
Params:
  • proxy – the proxy object
  • method – the method in the listener interface
See Also:
Returns:the result of applying the action to the target
/**
     * Extract the appropriate property value from the event and
     * pass it to the action associated with
     * this {@code EventHandler}.
     *
     * @param proxy the proxy object
     * @param method the method in the listener interface
     * @return the result of applying the action to the target
     *
     * @see EventHandler
     */
    public Object invoke(final Object proxy, final Method method, final Object[] arguments) {
        AccessControlContext acc = this.acc;
        if ((acc == null) && (System.getSecurityManager() != null)) {
            throw new SecurityException("AccessControlContext is not set");
        }
        return AccessController.doPrivileged(new PrivilegedAction<Object>() {
            public Object run() {
                return invokeInternal(proxy, method, arguments);
            }
        }, acc);
    }

    private Object invokeInternal(Object proxy, Method method, Object[] arguments) {
        String methodName = method.getName();
        if (method.getDeclaringClass() == Object.class)  {
            // Handle the Object public methods.
            if (methodName.equals("hashCode"))  {
                return System.identityHashCode(proxy);
            } else if (methodName.equals("equals")) {
                return (proxy == arguments[0] ? Boolean.TRUE : Boolean.FALSE);
            } else if (methodName.equals("toString")) {
                return proxy.getClass().getName() + '@' + Integer.toHexString(proxy.hashCode());
            }
        }

        if (listenerMethodName == null || listenerMethodName.equals(methodName)) {
            Class<?>[] argTypes = null;
            Object[] newArgs = null;

            if (eventPropertyName == null) {     // Nullary method.
                newArgs = new Object[]{};
                argTypes = new Class<?>[]{};
            }
            else {
                Object input = applyGetters(arguments[0], getEventPropertyName());
                newArgs = new Object[]{input};
                argTypes = new Class<?>[]{input == null ? null :
                                       input.getClass()};
            }
            try {
                int lastDot = action.lastIndexOf('.');
                if (lastDot != -1) {
                    target = applyGetters(target, action.substring(0, lastDot));
                    action = action.substring(lastDot + 1);
                }
                Method targetMethod = Statement.getMethod(
                             target.getClass(), action, argTypes);
                if (targetMethod == null) {
                    targetMethod = Statement.getMethod(target.getClass(),
                             "set" + NameGenerator.capitalize(action), argTypes);
                }
                if (targetMethod == null) {
                    String argTypeString = (argTypes.length == 0)
                        ? " with no arguments"
                        : " with argument " + argTypes[0];
                    throw new RuntimeException(
                        "No method called " + action + " on " +
                        target.getClass() + argTypeString);
                }
                return MethodUtil.invoke(targetMethod, target, newArgs);
            }
            catch (IllegalAccessException ex) {
                throw new RuntimeException(ex);
            }
            catch (InvocationTargetException ex) {
                Throwable th = ex.getTargetException();
                throw (th instanceof RuntimeException)
                        ? (RuntimeException) th
                        : new RuntimeException(th);
            }
        }
        return null;
    }

    
Creates an implementation of listenerInterface in which all of the methods in the listener interface apply the handler's action to the target. This method is implemented by calling the other, more general, implementation of the create method with both the eventPropertyName and the listenerMethodName taking the value null. Refer to 
the general version of create for a complete description of the action parameter. 
 To create an ActionListener that shows a JDialog with dialog.show(), one can write: 


EventHandler.create(ActionListener.class, dialog, "show")





Params:
  • listenerInterface – the listener interface to create a proxy for
  • target – the object that will perform the action
  • action – the name of a (possibly qualified) property or method on
       the target
Type parameters:
  • <T> – the type to create
Throws:
See Also:
Returns:an object that implements listenerInterface
/**
     * Creates an implementation of {@code listenerInterface} in which
     * <em>all</em> of the methods in the listener interface apply
     * the handler's {@code action} to the {@code target}. This
     * method is implemented by calling the other, more general,
     * implementation of the {@code create} method with both
     * the {@code eventPropertyName} and the {@code listenerMethodName}
     * taking the value {@code null}. Refer to
     * {@link java.beans.EventHandler#create(Class, Object, String, String)
     * the general version of create} for a complete description of
     * the {@code action} parameter.
     * <p>
     * To create an {@code ActionListener} that shows a
     * {@code JDialog} with {@code dialog.show()},
     * one can write:
     *
     *<blockquote>
     *<pre>
     *EventHandler.create(ActionListener.class, dialog, "show")
     *</pre>
     *</blockquote>
     *
     * @param <T> the type to create
     * @param listenerInterface the listener interface to create a proxy for
     * @param target the object that will perform the action
     * @param action the name of a (possibly qualified) property or method on
     *        the target
     * @return an object that implements {@code listenerInterface}
     *
     * @throws NullPointerException if {@code listenerInterface} is null
     * @throws NullPointerException if {@code target} is null
     * @throws NullPointerException if {@code action} is null
     * @throws IllegalArgumentException if creating a Proxy for
     *         {@code listenerInterface} fails for any of the restrictions
     *         specified by {@link Proxy#newProxyInstance}
     * @see #create(Class, Object, String, String)
     * @see Proxy#newProxyInstance
     */
    public static <T> T create(Class<T> listenerInterface,
                               Object target, String action)
    {
        return create(listenerInterface, target, action, null, null);
    }

    
/** Creates an implementation of listenerInterface in which all of the methods pass the value of the event expression, eventPropertyName, to the final method in the statement, action, which is applied to the target. This method is implemented by calling the more general, implementation of the create method with the listenerMethodName taking the value null. Refer to 
the general version of create for a complete description of the action and eventPropertyName parameters. 
 To create an ActionListener that sets the the text of a JLabel to the text value of the JTextField source of the incoming event, you can use the following code: 


EventHandler.create(ActionListener.class, label, "text", "source.text");




This is equivalent to the following code:



//Equivalent code using an inner class instead of EventHandler.
new ActionListener() {
   public void actionPerformed(ActionEvent event) {
       label.setText(((JTextField)(event.getSource())).getText());
    }
};





Params:
  • listenerInterface – the listener interface to create a proxy for
  • target – the object that will perform the action
  • action – the name of a (possibly qualified) property or method on
       the target
  • eventPropertyName – the (possibly qualified) name of a readable property of the incoming event
Type parameters:
  • <T> – the type to create
Throws:
See Also:
Returns:an object that implements listenerInterface
/**
    /**
     * Creates an implementation of {@code listenerInterface} in which
     * <em>all</em> of the methods pass the value of the event
     * expression, {@code eventPropertyName}, to the final method in the
     * statement, {@code action}, which is applied to the {@code target}.
     * This method is implemented by calling the
     * more general, implementation of the {@code create} method with
     * the {@code listenerMethodName} taking the value {@code null}.
     * Refer to
     * {@link java.beans.EventHandler#create(Class, Object, String, String)
     * the general version of create} for a complete description of
     * the {@code action} and {@code eventPropertyName} parameters.
     * <p>
     * To create an {@code ActionListener} that sets the
     * the text of a {@code JLabel} to the text value of
     * the {@code JTextField} source of the incoming event,
     * you can use the following code:
     *
     *<blockquote>
     *<pre>
     *EventHandler.create(ActionListener.class, label, "text", "source.text");
     *</pre>
     *</blockquote>
     *
     * This is equivalent to the following code:
     *<blockquote>
     *<pre>
//Equivalent code using an inner class instead of EventHandler.
     *new ActionListener() {
     *    public void actionPerformed(ActionEvent event) {
     *        label.setText(((JTextField)(event.getSource())).getText());
     *     }
     *};
     *</pre>
     *</blockquote>
     *
     * @param <T> the type to create
     * @param listenerInterface the listener interface to create a proxy for
     * @param target the object that will perform the action
     * @param action the name of a (possibly qualified) property or method on
     *        the target
     * @param eventPropertyName the (possibly qualified) name of a readable property of the incoming event
     *
     * @return an object that implements {@code listenerInterface}
     *
     * @throws NullPointerException if {@code listenerInterface} is null
     * @throws NullPointerException if {@code target} is null
     * @throws NullPointerException if {@code action} is null
     * @throws IllegalArgumentException if creating a Proxy for
     *         {@code listenerInterface} fails for any of the restrictions
     *         specified by {@link Proxy#newProxyInstance}
     * @see #create(Class, Object, String, String, String)
     * @see Proxy#newProxyInstance
     */
    public static <T> T create(Class<T> listenerInterface,
                               Object target, String action,
                               String eventPropertyName)
    {
        return create(listenerInterface, target, action, eventPropertyName, null);
    }

    
Creates an implementation of listenerInterface in which the method named listenerMethodName passes the value of the event expression, eventPropertyName, to the final method in the statement, action, which is applied to the target. All of the other listener methods do nothing. 
 The eventPropertyName string is used to extract a value from the incoming event object that is passed to the target method. The common case is the target method takes no arguments, in which case a value of null should be used for the eventPropertyName. Alternatively if you want the incoming event object passed directly to the target method use the empty string. The format of the eventPropertyName string is a sequence of methods or properties where each method or property is applied to the value returned by the preceding method starting from the incoming event object. The syntax is: propertyName{.propertyName}* where propertyName matches a method or property. For example, to extract the point property from a MouseEvent, you could use either "point" or "getPoint" as the eventPropertyName. To extract the "text" property from a MouseEvent with a JLabel source use any of the following as eventPropertyName: "source.text", "getSource.text" "getSource.getText" or "source.getText". If a method can not be found, or an exception is generated as part of invoking a method a RuntimeException will be thrown at dispatch time. For example, if the incoming event object is null, and eventPropertyName is non-null and not empty, a RuntimeException will be thrown. 
 The action argument is of the same format as the eventPropertyName argument where the last property name identifies either a method name or writable property. 
 If the listenerMethodName is null all methods in the interface trigger the action to be executed on the target. 
 For example, to create a MouseListener that sets the target object's origin property to the incoming MouseEvent's location (that's the value of mouseEvent.getPoint()) each time a mouse button is pressed, one would write: 


EventHandler.create(MouseListener.class, target, "origin", "point", "mousePressed");



 This is comparable to writing a MouseListener in which all of the methods except mousePressed are no-ops: 


//Equivalent code using an inner class instead of EventHandler.
new MouseAdapter() {
   public void mousePressed(MouseEvent e) {
       target.setOrigin(e.getPoint());
   }
};





Params:
  • listenerInterface – the listener interface to create a proxy for
  • target – the object that will perform the action
  • action – the name of a (possibly qualified) property or method on
       the target
  • eventPropertyName – the (possibly qualified) name of a readable property of the incoming event
  • listenerMethodName – the name of the method in the listener interface that should trigger the action
Type parameters:
  • <T> – the type to create
Throws:
See Also:
Returns:an object that implements listenerInterface
/**
     * Creates an implementation of {@code listenerInterface} in which
     * the method named {@code listenerMethodName}
     * passes the value of the event expression, {@code eventPropertyName},
     * to the final method in the statement, {@code action}, which
     * is applied to the {@code target}. All of the other listener
     * methods do nothing.
     * <p>
     * The {@code eventPropertyName} string is used to extract a value
     * from the incoming event object that is passed to the target
     * method.  The common case is the target method takes no arguments, in
     * which case a value of null should be used for the
     * {@code eventPropertyName}.  Alternatively if you want
     * the incoming event object passed directly to the target method use
     * the empty string.
     * The format of the {@code eventPropertyName} string is a sequence of
     * methods or properties where each method or
     * property is applied to the value returned by the preceding method
     * starting from the incoming event object.
     * The syntax is: {@code propertyName{.propertyName}*}
     * where {@code propertyName} matches a method or
     * property.  For example, to extract the {@code point}
     * property from a {@code MouseEvent}, you could use either
     * {@code "point"} or {@code "getPoint"} as the
     * {@code eventPropertyName}.  To extract the "text" property from
     * a {@code MouseEvent} with a {@code JLabel} source use any
     * of the following as {@code eventPropertyName}:
     * {@code "source.text"},
     * {@code "getSource.text" "getSource.getText"} or
     * {@code "source.getText"}.  If a method can not be found, or an
     * exception is generated as part of invoking a method a
     * {@code RuntimeException} will be thrown at dispatch time.  For
     * example, if the incoming event object is null, and
     * {@code eventPropertyName} is non-null and not empty, a
     * {@code RuntimeException} will be thrown.
     * <p>
     * The {@code action} argument is of the same format as the
     * {@code eventPropertyName} argument where the last property name
     * identifies either a method name or writable property.
     * <p>
     * If the {@code listenerMethodName} is {@code null}
     * <em>all</em> methods in the interface trigger the {@code action} to be
     * executed on the {@code target}.
     * <p>
     * For example, to create a {@code MouseListener} that sets the target
     * object's {@code origin} property to the incoming {@code MouseEvent}'s
     * location (that's the value of {@code mouseEvent.getPoint()}) each
     * time a mouse button is pressed, one would write:
     *<blockquote>
     *<pre>
     *EventHandler.create(MouseListener.class, target, "origin", "point", "mousePressed");
     *</pre>
     *</blockquote>
     *
     * This is comparable to writing a {@code MouseListener} in which all
     * of the methods except {@code mousePressed} are no-ops:
     *
     *<blockquote>
     *<pre>
//Equivalent code using an inner class instead of EventHandler.
     *new MouseAdapter() {
     *    public void mousePressed(MouseEvent e) {
     *        target.setOrigin(e.getPoint());
     *    }
     *};
     * </pre>
     *</blockquote>
     *
     * @param <T> the type to create
     * @param listenerInterface the listener interface to create a proxy for
     * @param target the object that will perform the action
     * @param action the name of a (possibly qualified) property or method on
     *        the target
     * @param eventPropertyName the (possibly qualified) name of a readable property of the incoming event
     * @param listenerMethodName the name of the method in the listener interface that should trigger the action
     *
     * @return an object that implements {@code listenerInterface}
     *
     * @throws NullPointerException if {@code listenerInterface} is null
     * @throws NullPointerException if {@code target} is null
     * @throws NullPointerException if {@code action} is null
     * @throws IllegalArgumentException if creating a Proxy for
     *         {@code listenerInterface} fails for any of the restrictions
     *         specified by {@link Proxy#newProxyInstance}
     * @see EventHandler
     * @see Proxy#newProxyInstance
     */
    public static <T> T create(Class<T> listenerInterface,
                               Object target, String action,
                               String eventPropertyName,
                               String listenerMethodName)
    {
        // Create this first to verify target/action are non-null
        final EventHandler handler = new EventHandler(target, action,
                                                     eventPropertyName,
                                                     listenerMethodName);
        if (listenerInterface == null) {
            throw new NullPointerException(
                          "listenerInterface must be non-null");
        }
        final ClassLoader loader = getClassLoader(listenerInterface);
        final Class<?>[] interfaces = {listenerInterface};
        return AccessController.doPrivileged(new PrivilegedAction<T>() {
            @SuppressWarnings("unchecked")
            public T run() {
                return (T) Proxy.newProxyInstance(loader, interfaces, handler);
            }
        });
    }

    private static ClassLoader getClassLoader(Class<?> type) {
        ReflectUtil.checkPackageAccess(type);
        ClassLoader loader = type.getClassLoader();
        if (loader == null) {
            loader = Thread.currentThread().getContextClassLoader(); // avoid use of BCP
            if (loader == null) {
                loader = ClassLoader.getSystemClassLoader();
            }
        }
        return loader;
    }
}