1 /*
2 * Copyright 2003-2005 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 package java.rmi.server;
26
27 import java.io.InvalidObjectException;
28 import java.lang.reflect.InvocationHandler;
29 import java.lang.reflect.Method;
30 import java.lang.reflect.Proxy;
31 import java.rmi.Remote;
32 import java.rmi.UnexpectedException;
33 import java.rmi.activation.Activatable;
34 import java.util.Map;
35 import java.util.WeakHashMap;
36 import sun.rmi.server.Util;
37 import sun.rmi.server.WeakClassHashMap;
38
39 /**
40 * An implementation of the <code>InvocationHandler</code> interface for
41 * use with Java Remote Method Invocation (Java RMI). This invocation
42 * handler can be used in conjunction with a dynamic proxy instance as a
43 * replacement for a pregenerated stub class.
44 *
45 * <p>Applications are not expected to use this class directly. A remote
46 * object exported to use a dynamic proxy with {@link UnicastRemoteObject}
47 * or {@link Activatable} has an instance of this class as that proxy's
48 * invocation handler.
49 *
50 * @author Ann Wollrath
51 * @since 1.5
52 **/
53 public class RemoteObjectInvocationHandler
54 extends RemoteObject
55 implements InvocationHandler
56 {
57 private static final long serialVersionUID = 2L;
58
59 /**
60 * A weak hash map, mapping classes to weak hash maps that map
61 * method objects to method hashes.
62 **/
63 private static final MethodToHash_Maps methodToHash_Maps =
64 new MethodToHash_Maps();
65
66 /**
67 * Creates a new <code>RemoteObjectInvocationHandler</code> constructed
68 * with the specified <code>RemoteRef</code>.
69 *
70 * @param ref the remote ref
71 *
72 * @throws NullPointerException if <code>ref</code> is <code>null</code>
73 **/
74 public RemoteObjectInvocationHandler(RemoteRef ref) {
75 super(ref);
76 if (ref == null) {
77 throw new NullPointerException();
78 }
79 }
80
81 /**
82 * Processes a method invocation made on the encapsulating
83 * proxy instance, <code>proxy</code>, and returns the result.
84 *
85 * <p><code>RemoteObjectInvocationHandler</code> implements this method
86 * as follows:
87 *
88 * <p>If <code>method</code> is one of the following methods, it
89 * is processed as described below:
90 *
91 * <ul>
92 *
93 * <li>{@link Object#hashCode Object.hashCode}: Returns the hash
94 * code value for the proxy.
95 *
96 * <li>{@link Object#equals Object.equals}: Returns <code>true</code>
97 * if the argument (<code>args[0]</code>) is an instance of a dynamic
98 * proxy class and this invocation handler is equal to the invocation
99 * handler of that argument, and returns <code>false</code> otherwise.
100 *
101 * <li>{@link Object#toString Object.toString}: Returns a string
102 * representation of the proxy.
103 * </ul>
104 *
105 * <p>Otherwise, a remote call is made as follows:
106 *
107 * <ul>
108 * <li>If <code>proxy</code> is not an instance of the interface
109 * {@link Remote}, then an {@link IllegalArgumentException} is thrown.
110 *
111 * <li>Otherwise, the {@link RemoteRef#invoke invoke} method is invoked
112 * on this invocation handler's <code>RemoteRef</code>, passing
113 * <code>proxy</code>, <code>method</code>, <code>args</code>, and the
114 * method hash (defined in section 8.3 of the "Java Remote Method
115 * Invocation (RMI) Specification") for <code>method</code>, and the
116 * result is returned.
117 *
118 * <li>If an exception is thrown by <code>RemoteRef.invoke</code> and
119 * that exception is a checked exception that is not assignable to any
120 * exception in the <code>throws</code> clause of the method
121 * implemented by the <code>proxy</code>'s class, then that exception
122 * is wrapped in an {@link UnexpectedException} and the wrapped
123 * exception is thrown. Otherwise, the exception thrown by
124 * <code>invoke</code> is thrown by this method.
125 * </ul>
126 *
127 * <p>The semantics of this method are unspecified if the
128 * arguments could not have been produced by an instance of some
129 * valid dynamic proxy class containing this invocation handler.
130 *
131 * @param proxy the proxy instance that the method was invoked on
132 * @param method the <code>Method</code> instance corresponding to the
133 * interface method invoked on the proxy instance
134 * @param args an array of objects containing the values of the
135 * arguments passed in the method invocation on the proxy instance, or
136 * <code>null</code> if the method takes no arguments
137 * @return the value to return from the method invocation on the proxy
138 * instance
139 * @throws Throwable the exception to throw from the method invocation
140 * on the proxy instance
141 * @see
142 **/
143 public Object invoke(Object proxy, Method method, Object[] args)
144 throws Throwable
145 {
146 if (method.getDeclaringClass() == Object.class) {
147 return invokeObjectMethod(proxy, method, args);
148 } else {
149 return invokeRemoteMethod(proxy, method, args);
150 }
151 }
152
153 /**
154 * Handles java.lang.Object methods.
155 **/
156 private Object invokeObjectMethod(Object proxy,
157 Method method,
158 Object[] args)
159 {
160 String name = method.getName();
161
162 if (name.equals("hashCode")) {
163 return hashCode();
164
165 } else if (name.equals("equals")) {
166 Object obj = args[0];
167 return
168 proxy == obj ||
169 (obj != null &&
170 Proxy.isProxyClass(obj.getClass()) &&
171 equals(Proxy.getInvocationHandler(obj)));
172
173 } else if (name.equals("toString")) {
174 return proxyToString(proxy);
175
176 } else {
177 throw new IllegalArgumentException(
178 "unexpected Object method: " + method);
179 }
180 }
181
182 /**
183 * Handles remote methods.
184 **/
185 private Object invokeRemoteMethod(Object proxy,
186 Method method,
187 Object[] args)
188 throws Exception
189 {
190 try {
191 if (!(proxy instanceof Remote)) {
192 throw new IllegalArgumentException(
193 "proxy not Remote instance");
194 }
195 return ref.invoke((Remote) proxy, method, args,
196 getMethodHash(method));
197 } catch (Exception e) {
198 if (!(e instanceof RuntimeException)) {
199 Class<?> cl = proxy.getClass();
200 try {
201 method = cl.getMethod(method.getName(),
202 method.getParameterTypes());
203 } catch (NoSuchMethodException nsme) {
204 throw (IllegalArgumentException)
205 new IllegalArgumentException().initCause(nsme);
206 }
207 Class<?> thrownType = e.getClass();
208 for (Class<?> declaredType : method.getExceptionTypes()) {
209 if (declaredType.isAssignableFrom(thrownType)) {
210 throw e;
211 }
212 }
213 e = new UnexpectedException("unexpected exception", e);
214 }
215 throw e;
216 }
217 }
218
219 /**
220 * Returns a string representation for a proxy that uses this invocation
221 * handler.
222 **/
223 private String proxyToString(Object proxy) {
224 Class<?>[] interfaces = proxy.getClass().getInterfaces();
225 if (interfaces.length == 0) {
226 return "Proxy[" + this + "]";
227 }
228 String iface = interfaces[0].getName();
229 if (iface.equals("java.rmi.Remote") && interfaces.length > 1) {
230 iface = interfaces[1].getName();
231 }
232 int dot = iface.lastIndexOf('.');
233 if (dot >= 0) {
234 iface = iface.substring(dot + 1);
235 }
236 return "Proxy[" + iface + "," + this + "]";
237 }
238
239 /**
240 * @throws InvalidObjectException unconditionally
241 **/
242 private void readObjectNoData() throws InvalidObjectException {
243 throw new InvalidObjectException("no data in stream; class: " +
244 this.getClass().getName());
245 }
246
247 /**
248 * Returns the method hash for the specified method. Subsequent calls
249 * to "getMethodHash" passing the same method argument should be faster
250 * since this method caches internally the result of the method to
251 * method hash mapping. The method hash is calculated using the
252 * "computeMethodHash" method.
253 *
254 * @param method the remote method
255 * @return the method hash for the specified method
256 */
257 private static long getMethodHash(Method method) {
258 return methodToHash_Maps.get(method.getDeclaringClass()).get(method);
259 }
260
261 /**
262 * A weak hash map, mapping classes to weak hash maps that map
263 * method objects to method hashes.
264 **/
265 private static class MethodToHash_Maps
266 extends WeakClassHashMap<Map<Method,Long>>
267 {
268 MethodToHash_Maps() {}
269
270 protected Map<Method,Long> computeValue(Class<?> remoteClass) {
271 return new WeakHashMap<Method,Long>() {
272 public synchronized Long get(Object key) {
273 Long hash = super.get(key);
274 if (hash == null) {
275 Method method = (Method) key;
276 hash = Util.computeMethodHash(method);
277 put(method, hash);
278 }
279 return hash;
280 }
281 };
282 }
283 }
284 }