001/* RemoteObjectInvocationHandler.java -- RMI stub replacement. 002 Copyright (C) 2005 Free Software Foundation, Inc. 003 004 This file is part of GNU Classpath. 005 006 GNU Classpath is free software; you can redistribute it and/or modify 007 it under the terms of the GNU General Public License as published by 008 the Free Software Foundation; either version 2, or (at your option) 009 any later version. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 012 WITHOUT ANY WARRANTY; without even the implied warranty of 013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014 General Public License for more details. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 019 02110-1301 USA. 020 021 Linking this library statically or dynamically with other modules is 022 making a combined work based on this library. Thus, the terms and 023 conditions of the GNU General Public License cover the whole 024 combination. 025 026 As a special exception, the copyright holders of this library give you 027 permission to link this library with independent modules to produce an 028 executable, regardless of the license terms of these independent 029 modules, and to copy and distribute the resulting executable under 030 terms of your choice, provided that you also meet, for each linked 031 independent module, the terms and conditions of the license of that 032 module. An independent module is a module which is not derived from 033 or based on this library. If you modify this library, you may extend 034 this exception to your version of the library, but you are not 035 obligated to do so. If you do not wish to do so, delete this 036 exception statement from your version. */ 037 038 039package java.rmi.server; 040 041import gnu.java.rmi.server.RMIHashes; 042 043import java.io.Serializable; 044import java.lang.reflect.InvocationHandler; 045import java.lang.reflect.Method; 046import java.lang.reflect.Proxy; 047import java.rmi.Remote; 048import java.rmi.RemoteException; 049import java.rmi.UnexpectedException; 050import java.rmi.registry.Registry; 051import java.rmi.server.RemoteObject; 052import java.rmi.server.RemoteRef; 053import java.rmi.server.UnicastRemoteObject; 054import java.util.Hashtable; 055 056/** 057 * Together with dynamic proxy instance, this class replaces the generated RMI 058 * stub (*_Stub) classes that (following 1.5 specification) should be no longer 059 * required. It is unusual to use the instances of this class directly in the 060 * user program. Such instances are automatically created and returned by 061 * {@link Registry} or {@link UnicastRemoteObject} methods if the remote 062 * reference is known but the corresponding stub class is not accessible. 063 * 064 * @see Registry#lookup 065 * 066 * @author Audrius Meskauskas (AudriusA@Bioinformatics.org) 067 */ 068public class RemoteObjectInvocationHandler extends RemoteObject implements 069 InvocationHandler, Remote, Serializable 070{ 071 /** 072 * Use the jdk 1.5 SUID for interoperability. 073 */ 074 static final long serialVersionUID = 2L; 075 076 /** 077 * The RMI method hash codes, computed once as described in the section 8.3 078 * of the Java Remote Method Invocation (RMI) Specification. 079 */ 080 static Hashtable methodHashCodes = new Hashtable(); 081 082 /** 083 * The empty class array to define parameters of .hashCode and .toString. 084 */ 085 static final Class[] noArgsC = new Class[0]; 086 087 /** 088 * The class array to define parameters of .equals 089 */ 090 static final Class[] anObjectC = new Class[] { Object.class }; 091 092 /** 093 * The empty object array to replace null when no args are passed. 094 */ 095 static final Object[] noArgs = new Object[0]; 096 097 /** 098 * Construct the remote invocation handler that forwards calls to the given 099 * remote object. 100 * 101 * @param reference the reference to the remote object where the method 102 * calls should be forwarded. 103 */ 104 public RemoteObjectInvocationHandler(RemoteRef reference) 105 { 106 super(reference); 107 } 108 109 /** 110 * Invoke the remote method. When the known method is invoked on a created RMI 111 * stub proxy class, the call is delivered to this method and then transferred 112 * to the {@link RemoteRef#invoke(Remote, Method, Object[], long)} of the 113 * remote reference that was passed in constructor. The methods are handled as 114 * following: 115 * <ul> 116 * <li> The toString() method is delegated to the passed proxy instance.</li> 117 * <li>The .equals method only returns true if the passed object is an 118 * instance of proxy class and its invocation handler is equal to this 119 * invocation handles.</li> 120 * <li>The .hashCode returns the hashCode of this invocation handler (if the.</li> 121 * <li>All other methods are converted to remote calls and forwarded to the 122 * remote reference. </li> 123 * </ul> 124 * 125 * @param proxyInstance 126 * the instance of the proxy stub 127 * @param method 128 * the method being invoked 129 * @param parameters 130 * the method parameters 131 * @return the method return value, returned by RemoteRef.invoke 132 * @throws IllegalAccessException 133 * if the passed proxy instance does not implement Remote interface. 134 * @throws UnexpectedException 135 * if remote call throws some exception, not listed in the 136 * <code>throws</code> clause of the method being called. 137 * @throws Throwable 138 * that is thrown by remote call, if that exception is listend in 139 * the <code>throws</code> clause of the method being called. 140 */ 141 public Object invoke(Object proxyInstance, Method method, Object[] parameters) 142 throws Throwable 143 { 144 if (!(proxyInstance instanceof Remote)) 145 { 146 String name = proxyInstance == null ? "null" 147 : proxyInstance.getClass().getName(); 148 throw new IllegalAccessException(name + " does not implement " 149 + Remote.class.getName()); 150 } 151 152 if (parameters == null) 153 parameters = noArgs; 154 155 String name = method.getName(); 156 switch (name.charAt(0)) 157 { 158 case 'e': 159 if (parameters.length == 1 && name.equals("equals") 160 && method.getParameterTypes()[0].equals(Object.class)) 161 { 162 if (parameters[0] instanceof Proxy) 163 { 164 Object handler = Proxy.getInvocationHandler(parameters[0]); 165 if (handler == null) 166 return Boolean.FALSE; 167 else 168 return handler.equals(this) ? Boolean.TRUE : Boolean.FALSE; 169 } 170 else 171 return Boolean.FALSE; 172 } 173 break; 174 case 'h': 175 if (parameters.length == 0 && name.equals("hashCode")) 176 { 177 int hashC = Proxy.getInvocationHandler(proxyInstance).hashCode(); 178 return new Integer(hashC); 179 } 180 break; 181 case 't': 182 if (parameters.length == 0 && name.equals("toString")) 183 return "Proxy stub:"+ref.remoteToString(); 184 break; 185 default: 186 break; 187 } 188 189 Long hash = (Long) methodHashCodes.get(method); 190 if (hash == null) 191 { 192 hash = new Long(RMIHashes.getMethodHash(method)); 193 methodHashCodes.put(method, hash); 194 } 195 196 try 197 { 198 return getRef().invoke((Remote) proxyInstance, method, parameters, 199 hash.longValue()); 200 } 201 catch (RuntimeException exception) 202 { 203 // RuntimeException is always supported. 204 throw exception; 205 } 206 catch (RemoteException exception) 207 { 208 // All remote methods can throw RemoteException. 209 throw exception; 210 } 211 catch (Error exception) 212 { 213 throw exception; 214 } 215 catch (Exception exception) 216 { 217 Class[] exceptions = method.getExceptionTypes(); 218 Class exceptionClass = exception.getClass(); 219 220 for (int i = 0; i < exceptions.length; i++) 221 { 222 if (exceptions[i].equals(exceptionClass)) 223 throw exception; 224 } 225 throw new UnexpectedException(method.getName(), exception); 226 } 227 } 228 229}