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 * Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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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 <code>EventHandler</code> 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</code> 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</code> for a
 * connection from a <code>JCheckBox</code> 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</code> class
 * handles only a subset of what is possible using inner
 * classes. However, <code>EventHandler</code> works better
 * with the long-term persistence scheme than inner classes.
 * Also, using <code>EventHandler</code> 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</code>
 * have such a small
 * footprint is that the <code>Proxy</code> class, on which
 * the <code>EventHandler</code> relies, shares implementations
 * of identical
 * interfaces. For example, if you use
 * the <code>EventHandler</code> <code>create</code> methods to make
 * all the <code>ActionListener</code>s in an application,
 * all the action listeners will be instances of a single class
 * (one created by the <code>Proxy</code> class).
 * In general, listeners based on
 * the <code>Proxy</code> 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</code>
 * instances.
 * Instead, you use one of the <code>EventHandler</code>
 * <code>create</code> methods to create
 * an object that implements a given listener interface.
 * This listener object uses an <code>EventHandler</code> 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</code> methods.
 *
 * <h2>Examples of Using EventHandler</h2>
 *
 * The simplest use of <code>EventHandler</code> 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</code>
 * that invokes the <code>toFront</code> method on an instance
 * of <code>javax.swing.JFrame</code>.
 *
 * <blockquote>
 *<pre>
 *myButton.addActionListener(
 * (ActionListener)EventHandler.create(ActionListener.class, frame, "toFront"));
 *</pre>
 * </blockquote>
 *
 * When <code>myButton</code> is pressed, the statement
 * <code>frame.toFront()</code> 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</code>
 * 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</code> 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</code> that
 * sets the <code>nextFocusableComponent</code> 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</code> that
 * just passes the incoming event object to the target's action.
 * If the fourth <code>EventHandler.create</code> 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</code>
 * 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</code> 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</code> 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</code> which is
 * defined as:
 * <pre>
 * public class MyTarget {
 * public void doIt(String);
 * public void doIt(Object);
 * }
 * </pre>
 * Then the method <code>doIt</code> 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 <code>EventHandler</code> object;
 * you generally use one of the <code>create</code> 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</code> and <code>listenerMethodName</code>
 * 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</code> is null
 * @throws NullPointerException if <code>action</code> 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.
 *
 * @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.
 *
 * @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.
 *
 * @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 <code>null</code> 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 <code>EventHandler</code>.
 *
 * @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 new Integer(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 <code>listenerInterface</code> in which
 * <em>all</em> of the methods in the listener interface apply
 * the handler's <code>action</code> to the <code>target</code>. This
 * method is implemented by calling the other, more general,
 * implementation of the <code>create</code> method with both
 * the <code>eventPropertyName</code> and the <code>listenerMethodName</code>
 * taking the value <code>null</code>. Refer to
 * {@link java.beans.EventHandler#create(Class, Object, String, String)
 * the general version of create} for a complete description of
 * the <code>action</code> parameter.
 * <p>
 * To create an <code>ActionListener</code> that shows a
 * <code>JDialog</code> with <code>dialog.show()</code>,
 * 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</code>
 *
 * @throws NullPointerException if <code>listenerInterface</code> is null
 * @throws NullPointerException if <code>target</code> is null
 * @throws NullPointerException if <code>action</code> is null
 *
 * @see #create(Class, Object, String, String)
 */
 public static <T> T create(Class<T> listenerInterface,
 Object target, String action)
 {
 return create(listenerInterface, target, action, null, null);
 }

 /**
 /**
 * Creates an implementation of <code>listenerInterface</code> in which
 * <em>all</em> of the methods pass the value of the event
 * expression, <code>eventPropertyName</code>, to the final method in the
 * statement, <code>action</code>, which is applied to the <code>target</code>.
 * This method is implemented by calling the
 * more general, implementation of the <code>create</code> method with
 * the <code>listenerMethodName</code> taking the value <code>null</code>.
 * Refer to
 * {@link java.beans.EventHandler#create(Class, Object, String, String)
 * the general version of create} for a complete description of
 * the <code>action</code> and <code>eventPropertyName</code> parameters.
 * <p>
 * To create an <code>ActionListener</code> that sets the
 * the text of a <code>JLabel</code> to the text value of
 * the <code>JTextField</code> 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</code>
 *
 * @throws NullPointerException if <code>listenerInterface</code> is null
 * @throws NullPointerException if <code>target</code> is null
 * @throws NullPointerException if <code>action</code> is null
 *
 * @see #create(Class, Object, String, String, String)
 */
 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 <code>listenerInterface</code> in which
 * the method named <code>listenerMethodName</code>
 * passes the value of the event expression, <code>eventPropertyName</code>,
 * to the final method in the statement, <code>action</code>, which
 * is applied to the <code>target</code>. All of the other listener
 * methods do nothing.
 * <p>
 * The <code>eventPropertyName</code> 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</code>. Alternatively if you want
 * the incoming event object passed directly to the target method use
 * the empty string.
 * The format of the <code>eventPropertyName</code> 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}*</code>
 * where <code>propertyName</code> matches a method or
 * property. For example, to extract the <code>point</code>
 * property from a <code>MouseEvent</code>, you could use either
 * <code>"point"</code> or <code>"getPoint"</code> as the
 * <code>eventPropertyName</code>. To extract the "text" property from
 * a <code>MouseEvent</code> with a <code>JLabel</code> source use any
 * of the following as <code>eventPropertyName</code>:
 * <code>"source.text"</code>,
 * <code>"getSource.text"</code> <code>"getSource.getText"</code> or
 * <code>"source.getText"</code>. If a method can not be found, or an
 * exception is generated as part of invoking a method a
 * <code>RuntimeException</code> will be thrown at dispatch time. For
 * example, if the incoming event object is null, and
 * <code>eventPropertyName</code> is non-null and not empty, a
 * <code>RuntimeException</code> will be thrown.
 * <p>
 * The <code>action</code> argument is of the same format as the
 * <code>eventPropertyName</code> argument where the last property name
 * identifies either a method name or writable property.
 * <p>
 * If the <code>listenerMethodName</code> is <code>null</code>
 * <em>all</em> methods in the interface trigger the <code>action</code> to be
 * executed on the <code>target</code>.
 * <p>
 * For example, to create a <code>MouseListener</code> that sets the target
 * object's <code>origin</code> property to the incoming <code>MouseEvent</code>'s
 * location (that's the value of <code>mouseEvent.getPoint()</code>) 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</code> in which all
 * of the methods except <code>mousePressed</code> 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</code>
 *
 * @throws NullPointerException if <code>listenerInterface</code> is null
 * @throws NullPointerException if <code>target</code> is null
 * @throws NullPointerException if <code>action</code> is null
 *
 * @see EventHandler
 */
 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;
 }
}