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authorupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
committerupstream source tree <ports@midipix.org>2015-03-15 20:14:05 -0400
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tree976dc5ab7fddf506dadce60ae936f43f58787092 /libjava/classpath/java/beans/EventHandler.java
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+/* java.beans.EventHandler
+ Copyright (C) 2004, 2005 Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING. If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library. Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module. An independent module is a module which is not derived from
+or based on this library. If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so. If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.beans;
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+/**
+ * <p>EventHandler forms a bridge between dynamically created listeners and
+ * arbitrary properties and methods.</p>
+ *
+ * <p>You can use this class to easily create listener implementations for
+ * some basic interactions between an event source and its target. Using
+ * the three static methods named <code>create</code> you can create
+ * these listener implementations.</p>
+ *
+ * <p>See the documentation of each method for usage examples.</p>
+ *
+ * @author Jerry Quinn (jlquinn@optonline.net)
+ * @author Robert Schuster (thebohemian@gmx.net)
+ * @since 1.4
+ */
+public class EventHandler implements InvocationHandler
+{
+ // The name of the method that will be implemented. If null, any method.
+ private String listenerMethod;
+
+ // The object to call action on.
+ private Object target;
+
+ // The name of the method or property setter in target.
+ private String action;
+
+ // The property to extract from an event passed to listenerMethod.
+ private String property;
+
+ // The target objects Class.
+ private Class targetClass;
+
+ // String class doesn't already have a capitalize routine.
+ private String capitalize(String s)
+ {
+ return s.substring(0, 1).toUpperCase() + s.substring(1);
+ }
+
+ /**
+ * Creates a new <code>EventHandler</code> instance.
+ *
+ * <p>Typical creation is done with the create method, not by knewing an
+ * EventHandler.</p>
+ *
+ * <p>This constructs an EventHandler that will connect the method
+ * listenerMethodName to target.action, extracting eventPropertyName from
+ * the first argument of listenerMethodName. and sending it to action.</p>
+ *
+ * <p>Throws a <code>NullPointerException</code> if the <code>target</code>
+ * argument is <code>null</code>.
+ *
+ * @param target Object that will perform the action.
+ * @param action A property or method of the target.
+ * @param eventPropertyName A readable property of the inbound event.
+ * @param listenerMethodName The listener method name triggering the action.
+ */
+ public EventHandler(Object target, String action, String eventPropertyName,
+ String listenerMethodName)
+ {
+ this.target = target;
+
+ // Retrieving the class is done for two reasons:
+ // 1) The class object is needed very frequently in the invoke() method.
+ // 2) The constructor should throw a NullPointerException if target is null.
+ targetClass = target.getClass();
+
+ this.action = action; // Turn this into a method or do we wait till
+ // runtime
+ property = eventPropertyName;
+ listenerMethod = listenerMethodName;
+ }
+
+ /**
+ * Returns the event property name.
+ */
+ public String getEventPropertyName()
+ {
+ return property;
+ }
+
+ /**
+ * Returns the listener's method name.
+ */
+ public String getListenerMethodName()
+ {
+ return listenerMethod;
+ }
+
+ /**
+ * Returns the target object.
+ */
+ public Object getTarget()
+ {
+ return target;
+ }
+
+ /**
+ * Returns the action method name.
+ */
+ public String getAction()
+ {
+ return action;
+ }
+
+ // Fetch a qualified property like a.b.c from object o. The properties can
+ // be boolean isProp or object getProp properties.
+ //
+ // Returns a length 2 array with the first entry containing the value
+ // extracted from the property, and the second entry contains the class of
+ // the method return type.
+ //
+ // We play this game because if the method returns a native type, the return
+ // value will be a wrapper. If we then take the type of the wrapper and use
+ // it to locate the action method that takes the native type, it won't match.
+ private Object[] getProperty(Object o, String prop)
+ {
+ // Isolate the first property name from a.b.c.
+ int pos;
+ String rest = null;
+ if ((pos = prop.indexOf('.')) != -1)
+ {
+ rest = prop.substring(pos + 1);
+ prop = prop.substring(0, pos);
+ }
+
+ // Find a method named getProp. It could be isProp instead.
+ Method getter;
+ try
+ {
+ // Look for boolean property getter isProperty
+ getter = o.getClass().getMethod("is" + capitalize(prop));
+ }
+ catch (NoSuchMethodException nsme1)
+ {
+ try {
+ // Look for regular property getter getProperty
+ getter = o.getClass().getMethod("get" + capitalize(prop));
+ } catch(NoSuchMethodException nsme2) {
+ try {
+ // Finally look for a method of the name prop
+ getter = o.getClass().getMethod(prop);
+ } catch(NoSuchMethodException nsme3) {
+ // Ok, give up with an intelligent hint for the user.
+ throw new RuntimeException("Method not called: Could not find a property or method '" + prop
+ + "' in " + o.getClass() + " while following the property argument '" + property + "'.");
+ }
+ }
+ }
+ try {
+ Object val = getter.invoke(o);
+
+ if (rest != null)
+ return getProperty(val, rest);
+
+ return new Object[] {val, getter.getReturnType()};
+ } catch(InvocationTargetException ite) {
+ throw new RuntimeException("Method not called: Property or method '" + prop + "' has thrown an exception.", ite);
+ } catch(IllegalAccessException iae) {
+ // This cannot happen because we looked up method with Class.getMethod()
+ // which returns public methods only.
+ throw (InternalError) new InternalError("Non-public method was invoked.").initCause(iae);
+ }
+ }
+
+ /**
+ * Invokes the <code>EventHandler</code>.
+ *
+ * <p>This method is normally called by the listener's proxy implementation.</p>
+ *
+ * @param proxy The listener interface that is implemented using
+ * the proxy mechanism.
+ * @param method The method that was called on the proxy instance.
+ * @param arguments The arguments which where given to the method.
+ * @throws Throwable <code>NoSuchMethodException</code> is thrown when the EventHandler's
+ * action method or property cannot be found.
+ */
+ public Object invoke(Object proxy, Method method, Object[] arguments)
+ {
+ try {
+ // The method instance of the target object. We have to find out which
+ // one we have to invoke.
+ Method actionMethod = null;
+
+ // Listener methods that weren't specified are ignored. If listenerMethod
+ // is null, then all listener methods are processed.
+ if (listenerMethod != null && !method.getName().equals(listenerMethod))
+ return null;
+
+ // If a property is defined we definitely need a valid object at
+ // arguments[0] that can be used to retrieve a value to which the
+ // property of the target gets set.
+ if(property != null) {
+ // Extracts the argument. We will let it fail with a NullPointerException
+ // the caller used a listener method that has no arguments.
+ Object event = arguments[0];
+
+ // Obtains the property XXX propertyType keeps showing up null - why?
+ // because the object inside getProperty changes, but the ref variable
+ // can't change this way, dolt! need a better way to get both values out
+ // - need method and object to do the invoke and get return type
+ Object v[] = getProperty(event, property);
+ Object[] args = new Object[] { v[0] };
+
+ // Changes the class array that controls which method signature we are going
+ // to look up in the target object.
+ Class[] argTypes = new Class[] { initClass((Class) v[1]) };
+
+ // Tries to find a setter method to which we can apply the
+ while(argTypes[0] != null) {
+ try
+ {
+ // Look for a property setter for action.
+ actionMethod = targetClass.getMethod("set" + capitalize(action), argTypes);
+
+ return actionMethod.invoke(target, args);
+ }
+ catch (NoSuchMethodException e)
+ {
+ // If action as property didn't work, try as method later.
+ }
+
+ argTypes[0] = nextClass(argTypes[0]);
+ }
+
+ // We could not find a suitable setter method. Now we try again interpreting
+ // action as the method name itself.
+ // Since we probably have changed the block local argTypes array
+ // we need to rebuild it.
+ argTypes = new Class[] { initClass((Class) v[1]) };
+
+ // Tries to find a setter method to which we can apply the
+ while(argTypes[0] != null) {
+ try
+ {
+ actionMethod = targetClass.getMethod(action, argTypes);
+
+ return actionMethod.invoke(target, args);
+ }
+ catch (NoSuchMethodException e)
+ {
+ }
+
+ argTypes[0] = nextClass(argTypes[0]);
+ }
+
+ throw new RuntimeException("Method not called: Could not find a public method named '"
+ + action + "' in target " + targetClass + " which takes a '"
+ + v[1] + "' argument or a property of this type.");
+ }
+
+ // If property was null we will search for a no-argument method here.
+ // Note: The ordering of method lookups is important because we want to prefer no-argument
+ // calls like the JDK does. This means if we have actionMethod() and actionMethod(Event) we will
+ // call the first *EVEN* if we have a valid argument for the second method. This is behavior compliant
+ // to the JDK.
+ // If actionMethod() is not available but there is a actionMethod(Event) we take this. That makes us
+ // more specification compliant than the JDK itself because this one will fail in such a case.
+ try
+ {
+ actionMethod = targetClass.getMethod(action);
+ }
+ catch(NoSuchMethodException nsme)
+ {
+ // Note: If we want to be really strict the specification says that a no-argument method should
+ // accept an EventObject (or subclass I guess). However since the official implementation is broken
+ // anyways, it's more flexible without the EventObject restriction and we are compatible on everything
+ // else this can stay this way.
+ if(arguments != null && arguments.length >= 1/* && arguments[0] instanceof EventObject*/) {
+ Class[] targetArgTypes = new Class[] { initClass(arguments[0].getClass()) };
+
+ while(targetArgTypes[0] != null) {
+ try
+ {
+ // If no property exists we expect the first element of the arguments to be
+ // an EventObject which is then applied to the target method.
+
+ actionMethod = targetClass.getMethod(action, targetArgTypes);
+
+ return actionMethod.invoke(target, new Object[] { arguments[0] });
+ }
+ catch(NoSuchMethodException nsme2)
+ {
+
+ }
+
+ targetArgTypes[0] = nextClass(targetArgTypes[0]);
+ }
+
+ }
+ }
+
+ // If we do not have a Method instance at this point this means that all our tries
+ // failed. The JDK throws an ArrayIndexOutOfBoundsException in this case.
+ if(actionMethod == null)
+ throw new ArrayIndexOutOfBoundsException(0);
+
+ // Invoke target.action(property)
+ return actionMethod.invoke(target);
+ } catch(InvocationTargetException ite) {
+ throw new RuntimeException(ite.getCause());
+ } catch(IllegalAccessException iae) {
+ // Cannot happen because we always use getMethod() which returns public
+ // methods only. Otherwise there is something seriously broken in
+ // GNU Classpath.
+ throw (InternalError) new InternalError("Non-public method was invoked.").initCause(iae);
+ }
+ }
+
+ /**
+ * <p>Returns the primitive type for every wrapper class or the
+ * class itself if it is no wrapper class.</p>
+ *
+ * <p>This is needed because to be able to find both kinds of methods:
+ * One that takes a wrapper class as the first argument and one that
+ * accepts a primitive instead.</p>
+ */
+ private Class initClass(Class klass) {
+ if(klass == Boolean.class) {
+ return Boolean.TYPE;
+ } else if(klass == Byte.class) {
+ return Byte.TYPE;
+ } else if(klass == Short.class) {
+ return Short.TYPE;
+ } else if(klass == Integer.class) {
+ return Integer.TYPE;
+ } else if(klass == Long.class) {
+ return Long.TYPE;
+ } else if(klass == Float.class) {
+ return Float.TYPE;
+ } else if(klass == Double.class) {
+ return Double.TYPE;
+ } else {
+ return klass;
+ }
+ }
+
+ /**
+ *
+ *
+ * @param klass
+ * @return
+ */
+ private Class nextClass(Class klass) {
+ if(klass == Boolean.TYPE) {
+ return Boolean.class;
+ } else if(klass == Byte.TYPE) {
+ return Byte.class;
+ } else if(klass == Short.TYPE) {
+ return Short.class;
+ } else if(klass == Integer.TYPE) {
+ return Integer.class;
+ } else if(klass == Long.TYPE) {
+ return Long.class;
+ } else if(klass == Float.TYPE) {
+ return Float.class;
+ } else if(klass == Double.TYPE) {
+ return Double.class;
+ } else {
+ return klass.getSuperclass();
+ }
+ }
+
+ /**
+ * <p>Constructs an implementation of <code>listenerInterface</code>
+ * to dispatch events.</p>
+ *
+ * <p>You can use such an implementation to simply call a public
+ * no-argument method of an arbitrary target object or to forward
+ * the first argument of the listener method to the target method.</p>
+ *
+ * <p>Call this method like:</p>
+ * <code>
+ * button.addActionListener((ActionListener)
+ * EventHandler.create(ActionListener.class, target, "dispose"));
+ * </code>
+ *
+ * <p>to achieve the following behavior:</p>
+ * <code>
+ * button.addActionListener(new ActionListener() {
+ * public void actionPerformed(ActionEvent ae) {
+ * target.dispose();
+ * }
+ * });
+ * </code>
+ *
+ * <p>That means if you need a listener implementation that simply calls a
+ * a no-argument method on a given instance for <strong>each</strong>
+ * method of the listener interface.</p>
+ *
+ * <p>Note: The <code>action</code> is interpreted as a method name. If your target object
+ * has no no-argument method of the given name the EventHandler tries to find
+ * a method with the same name but which can accept the first argument of the
+ * listener method. Usually this will be an event object but any other object
+ * will be forwarded, too. Keep in mind that using a property name instead of a
+ * real method here is wrong and will throw an <code>ArrayIndexOutOfBoundsException</code>
+ * whenever one of the listener methods is called.<p/>
+ *
+ * <p>The <code>EventHandler</code> will automatically convert primitives
+ * to their wrapper class and vice versa. Furthermore it will call
+ * a target method if it accepts a superclass of the type of the
+ * first argument of the listener method.</p>
+ *
+ * <p>In case that the method of the target object throws an exception
+ * it will be wrapped in a <code>RuntimeException</code> and thrown out
+ * of the listener method.</p>
+ *
+ * <p>In case that the method of the target object cannot be found an
+ * <code>ArrayIndexOutOfBoundsException</code> will be thrown when the
+ * listener method is invoked.</p>
+ *
+ * <p>A call to this method is equivalent to:
+ * <code>create(listenerInterface, target, action, null, null)</code></p>
+ *
+ * @param listenerInterface Listener interface to implement.
+ * @param target Object to invoke action on.
+ * @param action Target property or method to invoke.
+ * @return A constructed proxy object.
+ */
+ public static <T> T create(Class<T> listenerInterface, Object target,
+ String action)
+ {
+ return create(listenerInterface, target, action, null, null);
+ }
+
+ /**
+ * <p>Constructs an implementation of <code>listenerInterface</code>
+ * to dispatch events.</p>
+ *
+ * <p>Use this method if you want to create an implementation that retrieves
+ * a property value from the <b>first</b> argument of the listener method
+ * and applies it to the target's property or method. This first argument
+ * of the listener is usually an event object but any other object is
+ * valid, too.</p>
+ *
+ * <p>You can set the value of <code>eventPropertyName</code> to "prop"
+ * to denote the retrieval of a property named "prop" from the event
+ * object. In case that no such property exists the <code>EventHandler</code>
+ * will try to find a method with that name.</p>
+ *
+ * <p>If you set <code>eventPropertyName</code> to a value like this "a.b.c"
+ * <code>EventHandler</code> will recursively evaluate the properties "a", "b"
+ * and "c". Again if no property can be found the <code>EventHandler</code>
+ * tries a method name instead. This allows mixing the names, too: "a.toString"
+ * will retrieve the property "a" from the event object and will then call
+ * the method "toString" on it.</p>
+ *
+ * <p>An exception thrown in any of these methods will provoke a
+ * <code>RuntimeException</code> to be thrown which contains an
+ * <code>InvocationTargetException</code> containing the triggering exception.</p>
+ *
+ * <p>If you set <code>eventPropertyName</code> to a non-null value the
+ * <code>action</code> parameter will be interpreted as a property name
+ * or a method name of the target object.</p>
+ *
+ * <p>Any object retrieved from the event object and applied to the
+ * target will converted from primitives to their wrapper class or
+ * vice versa or applied to a method that accepts a superclass
+ * of the object.</p>
+ *
+ * <p>Examples:</p>
+ * <p>The following code:</p><code>
+ * button.addActionListener(
+ * new ActionListener() {
+ * public void actionPerformed(ActionEvent ae) {
+ * Object o = ae.getSource().getClass().getName();
+ * textField.setText((String) o);
+ * }
+ * });
+ * </code>
+ *
+ * <p>Can be expressed using the <code>EventHandler</code> like this:</p>
+ * <p>
+ * <code>button.addActionListener((ActionListener)
+ * EventHandler.create(ActionListener.class, textField, "text", "source.class.name");
+ * <code>
+ * </p>
+ *
+ * <p>As said above you can specify the target as a method, too:</p>
+ * <p>
+ * <code>button.addActionListener((ActionListener)
+ * EventHandler.create(ActionListener.class, textField, "setText", "source.class.name");
+ * <code>
+ * </p>
+ *
+ * <p>Furthermore you can use method names in the property:</p>
+ * <p>
+ * <code>button.addActionListener((ActionListener)
+ * EventHandler.create(ActionListener.class, textField, "setText", "getSource.getClass.getName");
+ * <code>
+ * </p>
+ *
+ * <p>Finally you can mix names:</p>
+ * <p>
+ * <code>button.addActionListener((ActionListener)
+ * EventHandler.create(ActionListener.class, textField, "setText", "source.getClass.name");
+ * <code>
+ * </p>
+ *
+ * <p>A call to this method is equivalent to:
+ * <code>create(listenerInterface, target, action, null, null)</code>
+ * </p>
+ *
+ * @param listenerInterface Listener interface to implement.
+ * @param target Object to invoke action on.
+ * @param action Target property or method to invoke.
+ * @param eventPropertyName Name of property to extract from event.
+ * @return A constructed proxy object.
+ */
+ public static <T> T create(Class<T> listenerInterface, Object target,
+ String action, String eventPropertyName)
+ {
+ return create(listenerInterface, target, action, eventPropertyName, null);
+ }
+
+ /**
+ * <p>Constructs an implementation of <code>listenerInterface</code>
+ * to dispatch events.</p>
+ *
+ * <p>Besides the functionality described for {@link create(Class, Object, String)}
+ * and {@link create(Class, Object, String, String)} this method allows you
+ * to filter the listener method that should have an effect. Look at these
+ * method's documentation for more information about the <code>EventHandler</code>'s
+ * usage.</p>
+ *
+ * <p>If you want to call <code>dispose</code> on a <code>JFrame</code> instance
+ * when the <code>WindowListener.windowClosing()</code> method was invoked use
+ * the following code:</p>
+ * <p>
+ * <code>
+ * EventHandler.create(WindowListener.class, jframeInstance, "dispose", null, "windowClosing");
+ * </code>
+ * </p>
+ *
+ * <p>A <code>NullPointerException</code> is thrown if the <code>listenerInterface</code>
+ * or <code>target</code> argument are <code>null</code>.
+ *
+ * @param listenerInterface Listener interface to implement.
+ * @param target Object to invoke action on.
+ * @param action Target method name to invoke.
+ * @param eventPropertyName Name of property to extract from event.
+ * @param listenerMethodName Listener method to implement.
+ * @return A constructed proxy object.
+ */
+ public static <T> T create(Class<T> listenerInterface, Object target,
+ String action, String eventPropertyName,
+ String listenerMethodName)
+ {
+ // Create EventHandler instance
+ EventHandler eh = new EventHandler(target, action, eventPropertyName,
+ listenerMethodName);
+
+ // Create proxy object passing in the event handler
+ Object proxy = Proxy.newProxyInstance(listenerInterface.getClassLoader(),
+ new Class<?>[] {listenerInterface},
+ eh);
+
+ return (T) proxy;
+ }
+}