1 /*
2 * Copyright 1997-1999 Sun Microsystems, Inc. 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. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package javax.activation;
27
28 import java.io;
29 import java.beans.Beans;
30
31 /**
32 * The CommandInfo class is used by CommandMap implementations to
33 * describe the results of command requests. It provides the requestor
34 * with both the verb requested, as well as an instance of the
35 * bean. There is also a method that will return the name of the
36 * class that implements the command but <i>it is not guaranteed to
37 * return a valid value</i>. The reason for this is to allow CommandMap
38 * implmentations that subclass CommandInfo to provide special
39 * behavior. For example a CommandMap could dynamically generate
40 * JavaBeans. In this case, it might not be possible to create an
41 * object with all the correct state information solely from the class
42 * name.
43 *
44 * @since 1.6
45 */
46
47 public class CommandInfo {
48 private String verb;
49 private String className;
50
51 /**
52 * The Constructor for CommandInfo.
53 * @param verb The command verb this CommandInfo decribes.
54 * @param className The command's fully qualified class name.
55 */
56 public CommandInfo(String verb, String className) {
57 this.verb = verb;
58 this.className = className;
59 }
60
61 /**
62 * Return the command verb.
63 *
64 * @return the command verb.
65 */
66 public String getCommandName() {
67 return verb;
68 }
69
70 /**
71 * Return the command's class name. <i>This method MAY return null in
72 * cases where a CommandMap subclassed CommandInfo for its
73 * own purposes.</i> In other words, it might not be possible to
74 * create the correct state in the command by merely knowing
75 * its class name. <b>DO NOT DEPEND ON THIS METHOD RETURNING
76 * A VALID VALUE!</b>
77 *
78 * @return The class name of the command, or <i>null</i>
79 */
80 public String getCommandClass() {
81 return className;
82 }
83
84 /**
85 * Return the instantiated JavaBean component.
86 * <p>
87 * Begin by instantiating the component with
88 * <code>Beans.instantiate()</code>.
89 * <p>
90 * If the bean implements the <code>javax.activation.CommandObject</code>
91 * interface, call its <code>setCommandContext</code> method.
92 * <p>
93 * If the DataHandler parameter is null, then the bean is
94 * instantiated with no data. NOTE: this may be useful
95 * if for some reason the DataHandler that is passed in
96 * throws IOExceptions when this method attempts to
97 * access its InputStream. It will allow the caller to
98 * retrieve a reference to the bean if it can be
99 * instantiated.
100 * <p>
101 * If the bean does NOT implement the CommandObject interface,
102 * this method will check if it implements the
103 * java.io.Externalizable interface. If it does, the bean's
104 * readExternal method will be called if an InputStream
105 * can be acquired from the DataHandler.<p>
106 *
107 * @param dh The DataHandler that describes the data to be
108 * passed to the command.
109 * @param loader The ClassLoader to be used to instantiate the bean.
110 * @return The bean
111 * @see java.beans.Beans#instantiate
112 * @see javax.activation.CommandObject
113 */
114 public Object getCommandObject(DataHandler dh, ClassLoader loader)
115 throws IOException, ClassNotFoundException {
116 Object new_bean = null;
117
118 // try to instantiate the bean
119 new_bean = java.beans.Beans.instantiate(loader, className);
120
121 // if we got one and it is a CommandObject
122 if (new_bean != null) {
123 if (new_bean instanceof CommandObject) {
124 ((CommandObject)new_bean).setCommandContext(verb, dh);
125 } else if (new_bean instanceof Externalizable) {
126 if (dh != null) {
127 InputStream is = dh.getInputStream();
128 if (is != null) {
129 ((Externalizable)new_bean).readExternal(
130 new ObjectInputStream(is));
131 }
132 }
133 }
134 }
135
136 return new_bean;
137 }
138 }