716 lines
29 KiB
Java
716 lines
29 KiB
Java
/*
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* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.beans;
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import java.lang.reflect.InvocationHandler;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Proxy;
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import java.lang.reflect.Method;
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import java.security.AccessControlContext;
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import java.security.AccessController;
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import java.security.PrivilegedAction;
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import sun.reflect.misc.MethodUtil;
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import sun.reflect.misc.ReflectUtil;
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/**
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* The <code>EventHandler</code> class provides
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* support for dynamically generating event listeners whose methods
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* execute a simple statement involving an incoming event object
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* and a target object.
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* <p>
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* The <code>EventHandler</code> class is intended to be used by interactive tools, such as
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* application builders, that allow developers to make connections between
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* beans. Typically connections are made from a user interface bean
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* (the event <em>source</em>)
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* to an application logic bean (the <em>target</em>). The most effective
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* connections of this kind isolate the application logic from the user
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* interface. For example, the <code>EventHandler</code> for a
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* connection from a <code>JCheckBox</code> to a method
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* that accepts a boolean value can deal with extracting the state
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* of the check box and passing it directly to the method so that
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* the method is isolated from the user interface layer.
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* <p>
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* Inner classes are another, more general way to handle events from
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* user interfaces. The <code>EventHandler</code> class
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* handles only a subset of what is possible using inner
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* classes. However, <code>EventHandler</code> works better
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* with the long-term persistence scheme than inner classes.
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* Also, using <code>EventHandler</code> in large applications in
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* which the same interface is implemented many times can
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* reduce the disk and memory footprint of the application.
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* <p>
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* The reason that listeners created with <code>EventHandler</code>
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* have such a small
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* footprint is that the <code>Proxy</code> class, on which
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* the <code>EventHandler</code> relies, shares implementations
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* of identical
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* interfaces. For example, if you use
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* the <code>EventHandler</code> <code>create</code> methods to make
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* all the <code>ActionListener</code>s in an application,
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* all the action listeners will be instances of a single class
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* (one created by the <code>Proxy</code> class).
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* In general, listeners based on
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* the <code>Proxy</code> class require one listener class
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* to be created per <em>listener type</em> (interface),
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* whereas the inner class
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* approach requires one class to be created per <em>listener</em>
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* (object that implements the interface).
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*
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* <p>
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* You don't generally deal directly with <code>EventHandler</code>
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* instances.
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* Instead, you use one of the <code>EventHandler</code>
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* <code>create</code> methods to create
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* an object that implements a given listener interface.
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* This listener object uses an <code>EventHandler</code> object
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* behind the scenes to encapsulate information about the
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* event, the object to be sent a message when the event occurs,
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* the message (method) to be sent, and any argument
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* to the method.
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* The following section gives examples of how to create listener
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* objects using the <code>create</code> methods.
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*
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* <h2>Examples of Using EventHandler</h2>
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*
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* The simplest use of <code>EventHandler</code> is to install
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* a listener that calls a method on the target object with no arguments.
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* In the following example we create an <code>ActionListener</code>
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* that invokes the <code>toFront</code> method on an instance
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* of <code>javax.swing.JFrame</code>.
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*
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* <blockquote>
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*<pre>
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*myButton.addActionListener(
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* (ActionListener)EventHandler.create(ActionListener.class, frame, "toFront"));
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*</pre>
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* </blockquote>
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*
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* When <code>myButton</code> is pressed, the statement
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* <code>frame.toFront()</code> will be executed. One could get
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* the same effect, with some additional compile-time type safety,
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* by defining a new implementation of the <code>ActionListener</code>
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* interface and adding an instance of it to the button:
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*
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* <blockquote>
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*<pre>
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//Equivalent code using an inner class instead of EventHandler.
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*myButton.addActionListener(new ActionListener() {
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* public void actionPerformed(ActionEvent e) {
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* frame.toFront();
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* }
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*});
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*</pre>
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* </blockquote>
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*
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* The next simplest use of <code>EventHandler</code> is
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* to extract a property value from the first argument
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* of the method in the listener interface (typically an event object)
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* and use it to set the value of a property in the target object.
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* In the following example we create an <code>ActionListener</code> that
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* sets the <code>nextFocusableComponent</code> property of the target
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* (myButton) object to the value of the "source" property of the event.
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*
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* <blockquote>
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*<pre>
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*EventHandler.create(ActionListener.class, myButton, "nextFocusableComponent", "source")
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*</pre>
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* </blockquote>
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*
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* This would correspond to the following inner class implementation:
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*
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* <blockquote>
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*<pre>
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//Equivalent code using an inner class instead of EventHandler.
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*new ActionListener() {
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* public void actionPerformed(ActionEvent e) {
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* myButton.setNextFocusableComponent((Component)e.getSource());
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* }
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*}
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*</pre>
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* </blockquote>
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*
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* It's also possible to create an <code>EventHandler</code> that
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* just passes the incoming event object to the target's action.
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* If the fourth <code>EventHandler.create</code> argument is
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* an empty string, then the event is just passed along:
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*
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* <blockquote>
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*<pre>
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*EventHandler.create(ActionListener.class, target, "doActionEvent", "")
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*</pre>
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* </blockquote>
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*
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* This would correspond to the following inner class implementation:
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*
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* <blockquote>
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*<pre>
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//Equivalent code using an inner class instead of EventHandler.
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*new ActionListener() {
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* public void actionPerformed(ActionEvent e) {
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* target.doActionEvent(e);
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* }
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*}
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*</pre>
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* </blockquote>
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*
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* Probably the most common use of <code>EventHandler</code>
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* is to extract a property value from the
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* <em>source</em> of the event object and set this value as
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* the value of a property of the target object.
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* In the following example we create an <code>ActionListener</code> that
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* sets the "label" property of the target
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* object to the value of the "text" property of the
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* source (the value of the "source" property) of the event.
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*
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* <blockquote>
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*<pre>
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*EventHandler.create(ActionListener.class, myButton, "label", "source.text")
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*</pre>
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* </blockquote>
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*
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* This would correspond to the following inner class implementation:
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*
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* <blockquote>
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*<pre>
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//Equivalent code using an inner class instead of EventHandler.
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*new ActionListener {
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* public void actionPerformed(ActionEvent e) {
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* myButton.setLabel(((JTextField)e.getSource()).getText());
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* }
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*}
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*</pre>
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* </blockquote>
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*
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* The event property may be "qualified" with an arbitrary number
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* of property prefixes delimited with the "." character. The "qualifying"
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* names that appear before the "." characters are taken as the names of
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* properties that should be applied, left-most first, to
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* the event object.
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* <p>
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* For example, the following action listener
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*
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* <blockquote>
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*<pre>
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*EventHandler.create(ActionListener.class, target, "a", "b.c.d")
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*</pre>
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* </blockquote>
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*
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* might be written as the following inner class
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* (assuming all the properties had canonical getter methods and
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* returned the appropriate types):
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*
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* <blockquote>
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*<pre>
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//Equivalent code using an inner class instead of EventHandler.
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*new ActionListener {
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* public void actionPerformed(ActionEvent e) {
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* target.setA(e.getB().getC().isD());
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* }
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*}
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*</pre>
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* </blockquote>
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* The target property may also be "qualified" with an arbitrary number
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* of property prefixs delimited with the "." character. For example, the
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* following action listener:
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* <pre>
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* EventHandler.create(ActionListener.class, target, "a.b", "c.d")
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* </pre>
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* might be written as the following inner class
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* (assuming all the properties had canonical getter methods and
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* returned the appropriate types):
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* <pre>
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* //Equivalent code using an inner class instead of EventHandler.
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* new ActionListener {
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* public void actionPerformed(ActionEvent e) {
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* target.getA().setB(e.getC().isD());
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* }
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*}
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*</pre>
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* <p>
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* As <code>EventHandler</code> ultimately relies on reflection to invoke
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* a method we recommend against targeting an overloaded method. For example,
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* if the target is an instance of the class <code>MyTarget</code> which is
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* defined as:
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* <pre>
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* public class MyTarget {
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* public void doIt(String);
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* public void doIt(Object);
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* }
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* </pre>
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* Then the method <code>doIt</code> is overloaded. EventHandler will invoke
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* the method that is appropriate based on the source. If the source is
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* null, then either method is appropriate and the one that is invoked is
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* undefined. For that reason we recommend against targeting overloaded
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* methods.
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*
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* @see java.lang.reflect.Proxy
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* @see java.util.EventObject
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*
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* @since 1.4
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*
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* @author Mark Davidson
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* @author Philip Milne
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* @author Hans Muller
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*
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*/
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public class EventHandler implements InvocationHandler {
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private Object target;
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private String action;
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private final String eventPropertyName;
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private final String listenerMethodName;
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private final AccessControlContext acc = AccessController.getContext();
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/**
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* Creates a new <code>EventHandler</code> object;
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* you generally use one of the <code>create</code> methods
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* instead of invoking this constructor directly. Refer to
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* {@link java.beans.EventHandler#create(Class, Object, String, String)
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* the general version of create} for a complete description of
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* the <code>eventPropertyName</code> and <code>listenerMethodName</code>
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* parameter.
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*
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* @param target the object that will perform the action
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* @param action the name of a (possibly qualified) property or method on
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* the target
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* @param eventPropertyName the (possibly qualified) name of a readable property of the incoming event
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* @param listenerMethodName the name of the method in the listener interface that should trigger the action
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*
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* @throws NullPointerException if <code>target</code> is null
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* @throws NullPointerException if <code>action</code> is null
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*
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* @see EventHandler
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* @see #create(Class, Object, String, String, String)
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* @see #getTarget
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* @see #getAction
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* @see #getEventPropertyName
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* @see #getListenerMethodName
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*/
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@ConstructorProperties({"target", "action", "eventPropertyName", "listenerMethodName"})
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public EventHandler(Object target, String action, String eventPropertyName, String listenerMethodName) {
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this.target = target;
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this.action = action;
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if (target == null) {
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throw new NullPointerException("target must be non-null");
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}
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if (action == null) {
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throw new NullPointerException("action must be non-null");
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}
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this.eventPropertyName = eventPropertyName;
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this.listenerMethodName = listenerMethodName;
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}
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/**
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* Returns the object to which this event handler will send a message.
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*
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* @return the target of this event handler
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* @see #EventHandler(Object, String, String, String)
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*/
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public Object getTarget() {
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return target;
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}
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/**
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* Returns the name of the target's writable property
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* that this event handler will set,
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* or the name of the method that this event handler
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* will invoke on the target.
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*
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* @return the action of this event handler
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* @see #EventHandler(Object, String, String, String)
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*/
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public String getAction() {
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return action;
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}
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/**
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* Returns the property of the event that should be
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* used in the action applied to the target.
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*
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* @return the property of the event
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*
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* @see #EventHandler(Object, String, String, String)
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*/
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public String getEventPropertyName() {
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return eventPropertyName;
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}
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/**
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* Returns the name of the method that will trigger the action.
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* A return value of <code>null</code> signifies that all methods in the
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* listener interface trigger the action.
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*
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* @return the name of the method that will trigger the action
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*
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* @see #EventHandler(Object, String, String, String)
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*/
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public String getListenerMethodName() {
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return listenerMethodName;
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}
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private Object applyGetters(Object target, String getters) {
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if (getters == null || getters.equals("")) {
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return target;
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}
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int firstDot = getters.indexOf('.');
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if (firstDot == -1) {
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firstDot = getters.length();
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}
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String first = getters.substring(0, firstDot);
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String rest = getters.substring(Math.min(firstDot + 1, getters.length()));
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try {
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Method getter = null;
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if (target != null) {
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getter = Statement.getMethod(target.getClass(),
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"get" + NameGenerator.capitalize(first),
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new Class<?>[]{});
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if (getter == null) {
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getter = Statement.getMethod(target.getClass(),
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"is" + NameGenerator.capitalize(first),
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new Class<?>[]{});
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}
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if (getter == null) {
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getter = Statement.getMethod(target.getClass(), first, new Class<?>[]{});
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}
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}
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if (getter == null) {
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throw new RuntimeException("No method called: " + first +
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" defined on " + target);
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}
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Object newTarget = MethodUtil.invoke(getter, target, new Object[]{});
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return applyGetters(newTarget, rest);
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}
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catch (Exception e) {
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throw new RuntimeException("Failed to call method: " + first +
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" on " + target, e);
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}
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}
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/**
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* Extract the appropriate property value from the event and
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* pass it to the action associated with
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* this <code>EventHandler</code>.
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*
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* @param proxy the proxy object
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* @param method the method in the listener interface
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* @return the result of applying the action to the target
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*
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* @see EventHandler
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*/
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public Object invoke(final Object proxy, final Method method, final Object[] arguments) {
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AccessControlContext acc = this.acc;
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if ((acc == null) && (System.getSecurityManager() != null)) {
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throw new SecurityException("AccessControlContext is not set");
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}
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return AccessController.doPrivileged(new PrivilegedAction<Object>() {
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public Object run() {
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return invokeInternal(proxy, method, arguments);
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}
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}, acc);
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}
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private Object invokeInternal(Object proxy, Method method, Object[] arguments) {
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String methodName = method.getName();
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if (method.getDeclaringClass() == Object.class) {
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// Handle the Object public methods.
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if (methodName.equals("hashCode")) {
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return new Integer(System.identityHashCode(proxy));
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} else if (methodName.equals("equals")) {
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return (proxy == arguments[0] ? Boolean.TRUE : Boolean.FALSE);
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} else if (methodName.equals("toString")) {
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return proxy.getClass().getName() + '@' + Integer.toHexString(proxy.hashCode());
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}
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}
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if (listenerMethodName == null || listenerMethodName.equals(methodName)) {
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Class[] argTypes = null;
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Object[] newArgs = null;
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if (eventPropertyName == null) { // Nullary method.
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newArgs = new Object[]{};
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argTypes = new Class<?>[]{};
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}
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else {
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Object input = applyGetters(arguments[0], getEventPropertyName());
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newArgs = new Object[]{input};
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argTypes = new Class<?>[]{input == null ? null :
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input.getClass()};
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}
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try {
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int lastDot = action.lastIndexOf('.');
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if (lastDot != -1) {
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target = applyGetters(target, action.substring(0, lastDot));
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action = action.substring(lastDot + 1);
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}
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Method targetMethod = Statement.getMethod(
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target.getClass(), action, argTypes);
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if (targetMethod == null) {
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targetMethod = Statement.getMethod(target.getClass(),
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"set" + NameGenerator.capitalize(action), argTypes);
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}
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if (targetMethod == null) {
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String argTypeString = (argTypes.length == 0)
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? " with no arguments"
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: " with argument " + argTypes[0];
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throw new RuntimeException(
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"No method called " + action + " on " +
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target.getClass() + argTypeString);
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}
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return MethodUtil.invoke(targetMethod, target, newArgs);
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}
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catch (IllegalAccessException ex) {
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throw new RuntimeException(ex);
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}
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catch (InvocationTargetException ex) {
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Throwable th = ex.getTargetException();
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throw (th instanceof RuntimeException)
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? (RuntimeException) th
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: new RuntimeException(th);
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}
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}
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return null;
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}
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/**
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* Creates an implementation of <code>listenerInterface</code> in which
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* <em>all</em> of the methods in the listener interface apply
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* 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;
|
|
}
|
|
}
|