1 /*
2 * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /**
27 * Contains classes related to developing <em>beans</em> -- components based on
28 * the JavaBeans architecture. A few of the classes are used by beans
29 * while they run in an application. For example, the event classes are used by
30 * beans that fire property and vetoable change events (see
31 * {@link java.beans.PropertyChangeEvent}). However, most of the classes in this
32 * package are meant to be used by a bean editor (that is, a development
33 * environment for customizing and putting together beans to create an
34 * application). In particular, these classes help the bean editor create a user
35 * interface that the user can use to customize the bean. For example, a bean
36 * may contain a property of a special type that a bean editor may not know how
37 * to handle. By using the {@code PropertyEditor} interface, a bean developer
38 * can provide an editor for this special type.
39 * <p>
40 * To minimize the resources used by a bean, the classes used by bean editors
41 * are loaded only when the bean is being edited. They are not needed while the
42 * bean is running in an application and therefore not loaded. This information
43 * is kept in what's called a bean-info (see {@link java.beans.BeanInfo}).
44 * <p>
45 * Unless explicitly stated, null values or empty Strings are not valid
46 * parameters for the methods in this package. You may expect to see exceptions
47 * if these parameters are used.
48 *
49 * <h2>Long-Term Persistence</h2>
50 * As of v1.4, the {@code java.beans} package provides support for <em>long-term
51 * persistence</em> -- reading and writing a bean as a textual representation of
52 * its property values. The property values are treated as beans, and are
53 * recursively read or written to capture their publicly available state. This
54 * approach is suitable for long-term storage because it relies only on public
55 * API, rather than the likely-to-change private implementation.
56 *
57 * <blockquote><hr><b>Note:</b> The persistence scheme cannot automatically
58 * instantiate custom inner classes, such as you might use for event handlers.
59 * By using the {@link java.beans.EventHandler} class instead of inner classes
60 * for custom event handlers, you can avoid this problem.<hr></blockquote>
61 * <p>
62 * You read and write beans in XML format using the
63 * {@link java.beans.XMLDecoder} and {@link java.beans.XMLEncoder} classes,
64 * respectively. One notable feature of the persistence scheme is that reading
65 * in a bean requires no special knowledge of the bean.
66 * <p>
67 * Writing out a bean, on the other hand, sometimes requires special knowledge
68 * of the bean's type. If the bean's state can be expressed using only the
69 * no-argument constructor and public getter and setter methods for properties,
70 * no special knowledge is required. Otherwise, the bean requires a custom
71 * <em>persistence delegate</em> -- an object that is in charge of writing out
72 * beans of a particular type. All classes provided in the JDK that descend from
73 * {@code java.awt.Component}, as well as all their properties, automatically
74 * have persistence delegates.
75 * <p>
76 * If you need (or choose) to provide a persistence delegate for a bean, you can
77 * do so either by using a {@link java.beans.DefaultPersistenceDelegate}
78 * instance or by creating your own subclass of {@code PersistenceDelegate}. If
79 * the only reason a bean needs a persistence delegate is because you want to
80 * invoke the bean's constructor with property values as arguments, you can
81 * create the bean's persistence delegate with the one-argument
82 * {@code DefaultPersistenceDelegate} constructor. Otherwise, you need to
83 * implement your own persistence delegate, for which you're likely to need the
84 * following classes:
85 * <dl>
86 * <dt>{@link java.beans.PersistenceDelegate}</dt>
87 * <dd>The abstract class from which all persistence delegates descend. Your
88 * subclass should use its knowledge of the bean's type to provide whatever
89 * {@code Statement}s and {@code Expression}s are necessary to create the
90 * bean and restore its state.</dd>
91 * <dt>{@link java.beans.Statement}</dt>
92 * <dd>Represents the invocation of a single method on an object. Includes
93 * a set of arguments to the method.</dd>
94 * <dt>{@link java.beans.Expression}</dt>
95 * <dd>A subclass of {@code Statement} used for methods that return a
96 * value.</dd>
97 * </dl>
98 * <p>
99 * Once you create a persistence delegate, you register it using the
100 * {@code setPersistenceDelegate} method of {@code XMLEncoder}.
101 *
102 * <h2>Related Documentation</h2>
103 * For overview, architecture, and tutorial documentation, please see:
104 * <ul>
105 * <li><a href="https://docs.oracle.com/javase/tutorial/javabeans/">
106 * JavaBeans</a>, a trail in <em>The Java Tutorial</em>.</li>
107 * <li><a href="http://www.oracle.com/technetwork/java/persistence2-141443.html">
108 * Long-Term Persistence</a>, an article in
109 * <em>The Swing Connection</em>.</li>
110 * </ul>
111 */
112 package java.beans;