1 /*
2 * Copyright (c) 1997, 2016, 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 package javax.activation;
27
28 import java.io.*;
29 import java.lang.reflect.InvocationTargetException;
30 import java.lang.reflect.Method;
31 import java.security.AccessController;
32 import java.security.PrivilegedAction;
33
34 /**
35 * The CommandInfo class is used by CommandMap implementations to
36 * describe the results of command requests. It provides the requestor
37 * with both the verb requested, as well as an instance of the
38 * bean. There is also a method that will return the name of the
39 * class that implements the command but <i>it is not guaranteed to
40 * return a valid value</i>. The reason for this is to allow CommandMap
41 * implmentations that subclass CommandInfo to provide special
42 * behavior. For example a CommandMap could dynamically generate
43 * JavaBeans. In this case, it might not be possible to create an
44 * object with all the correct state information solely from the class
45 * name.
46 *
47 * @since 1.6
48 */
49
50 public class CommandInfo {
51 private String verb;
52 private String className;
53
54 /**
55 * The Constructor for CommandInfo.
56 * @param verb The command verb this CommandInfo decribes.
57 * @param className The command's fully qualified class name.
58 */
59 public CommandInfo(String verb, String className) {
60 this.verb = verb;
61 this.className = className;
62 }
63
64 /**
65 * Return the command verb.
66 *
67 * @return the command verb.
68 */
69 public String getCommandName() {
70 return verb;
71 }
72
73 /**
74 * Return the command's class name. <i>This method MAY return null in
75 * cases where a CommandMap subclassed CommandInfo for its
76 * own purposes.</i> In other words, it might not be possible to
77 * create the correct state in the command by merely knowing
78 * its class name. <b>DO NOT DEPEND ON THIS METHOD RETURNING
79 * A VALID VALUE!</b>
80 *
81 * @return The class name of the command, or <i>null</i>
82 */
83 public String getCommandClass() {
84 return className;
85 }
86
87 /**
88 * Return the instantiated JavaBean component.
89 * <p>
90 * If {@code java.beans.Beans} is visible then it's
91 * {@code java.beans.Beans#instantiate} method is invoked to instantiate
92 * the component as a JavaBeans component.
93 * When {@code java.beans.Beans} is not visible (when {@code java.desktop}
94 * module is not readable or when the runtime image does not contain the
95 * {@code java.desktop} module) then the command's class is loaded and
96 * instantiated with its public no-args constructor.
97 * <p>
98 * The component class needs to be public.
99 * <p>
100 * If the bean implements the {@code javax.activation.CommandObject}
101 * interface, call its {@code setCommandContext} method.
102 * <p>
103 * If the DataHandler parameter is null, then the bean is
104 * instantiated with no data. NOTE: this may be useful
105 * if for some reason the DataHandler that is passed in
106 * throws IOExceptions when this method attempts to
107 * access its InputStream. It will allow the caller to
108 * retrieve a reference to the bean if it can be
109 * instantiated.
110 * <p>
111 * If the bean does NOT implement the CommandObject interface,
112 * this method will check if it implements the
113 * java.io.Externalizable interface. If it does, the bean's
114 * readExternal method will be called if an InputStream
115 * can be acquired from the DataHandler.<p>
116 *
117 * @param dh The DataHandler that describes the data to be
118 * passed to the command.
119 * @param loader The ClassLoader to be used to instantiate the bean.
120 * @return The bean
121 * @see java.beans.Beans#instantiate
122 * @see javax.activation.CommandObject
123 */
124 public Object getCommandObject(DataHandler dh, ClassLoader loader)
125 throws IOException, ClassNotFoundException {
126 Object new_bean = null;
127
128 // try to instantiate the bean
129 new_bean = Beans.instantiate(loader, className);
130
131 // if we got one and it is a CommandObject
132 if (new_bean != null) {
133 if (new_bean instanceof CommandObject) {
134 ((CommandObject)new_bean).setCommandContext(verb, dh);
135 } else if (new_bean instanceof Externalizable) {
136 if (dh != null) {
137 InputStream is = dh.getInputStream();
138 if (is != null) {
139 ((Externalizable)new_bean).readExternal(
140 new ObjectInputStream(is));
141 }
142 }
143 }
144 }
145
146 return new_bean;
147 }
148
149 /**
150 * Helper class to invoke Beans.instantiate reflectively or the equivalent
151 * with core reflection when module java.desktop is not readable.
152 */
153 private static final class Beans {
154 static final Method instantiateMethod;
155
156 static {
157 Method m;
158 try {
159 Class<?> c = Class.forName("java.beans.Beans");
160 m = c.getDeclaredMethod("instantiate", ClassLoader.class, String.class);
161 } catch (ClassNotFoundException e) {
162 m = null;
163 } catch (NoSuchMethodException e) {
164 m = null;
165 }
166 instantiateMethod = m;
167 }
168
169 /**
170 * Equivalent to invoking java.beans.Beans.instantiate(loader, cn)
171 */
172 static Object instantiate(ClassLoader loader, String cn)
173 throws IOException, ClassNotFoundException {
174
175 Exception exception;
176
177 if (instantiateMethod != null) {
178
179 // invoke Beans.instantiate
180 try {
181 return instantiateMethod.invoke(null, loader, cn);
182 } catch (InvocationTargetException e) {
183 exception = e;
184 } catch (IllegalAccessException e) {
185 exception = e;
186 }
187
188 } else {
189
190 SecurityManager security = System.getSecurityManager();
191 if (security != null) {
192 // if it's ok with the SecurityManager, it's ok with me.
193 String cname = cn.replace('/', '.');
194 if (cname.startsWith("[")) {
195 int b = cname.lastIndexOf('[') + 2;
196 if (b > 1 && b < cname.length()) {
197 cname = cname.substring(b);
198 }
199 }
200 int i = cname.lastIndexOf('.');
201 if (i != -1) {
202 security.checkPackageAccess(cname.substring(0, i));
203 }
204 }
205
206 // Beans.instantiate specified to use SCL when loader is null
207 if (loader == null) {
208 loader = (ClassLoader)
209 AccessController.doPrivileged(new PrivilegedAction() {
210 public Object run() {
211 ClassLoader cl = null;
212 try {
213 cl = ClassLoader.getSystemClassLoader();
214 } catch (SecurityException ex) { }
215 return cl;
216 }
217 });
218 }
219 Class<?> beanClass = Class.forName(cn, false, loader);
220 try {
221 return beanClass.getDeclaredConstructor().newInstance();
222 } catch (Exception ex) {
223 throw new ClassNotFoundException(beanClass + ": " + ex, ex);
224 }
225
226 }
227 return null;
228 }
229 }
230 }