J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1997-2003 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 sun.rmi.server; |
| 27 | |
| 28 | import java.io.IOException; |
| 29 | import java.io.ObjectInput; |
| 30 | import java.io.ObjectOutput; |
| 31 | import java.lang.reflect.Proxy; |
| 32 | import java.net.MalformedURLException; |
| 33 | import java.net.URL; |
| 34 | import java.rmi.*; |
| 35 | import java.rmi.activation.*; |
| 36 | import java.rmi.server.Operation; |
| 37 | import java.rmi.server.RMIClassLoader; |
| 38 | import java.rmi.server.RemoteCall; |
| 39 | import java.rmi.server.RemoteObject; |
| 40 | import java.rmi.server.RemoteObjectInvocationHandler; |
| 41 | import java.rmi.server.RemoteRef; |
| 42 | import java.rmi.server.RemoteStub; |
| 43 | |
| 44 | public class ActivatableRef implements RemoteRef { |
| 45 | |
| 46 | private static final long serialVersionUID = 7579060052569229166L; |
| 47 | |
| 48 | protected ActivationID id; |
| 49 | protected RemoteRef ref; |
| 50 | transient boolean force = false; |
| 51 | |
| 52 | private static final int MAX_RETRIES = 3; |
| 53 | private static final String versionComplaint = |
| 54 | "activation requires 1.2 stubs"; |
| 55 | |
| 56 | /** |
| 57 | * Create a new (empty) ActivatableRef |
| 58 | */ |
| 59 | public ActivatableRef() |
| 60 | {} |
| 61 | |
| 62 | /** |
| 63 | * Create a ActivatableRef with the specified id |
| 64 | */ |
| 65 | public ActivatableRef(ActivationID id, RemoteRef ref) |
| 66 | { |
| 67 | this.id = id; |
| 68 | this.ref = ref; |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * Returns the stub for the remote object whose class is |
| 73 | * specified in the activation descriptor. The ActivatableRef |
| 74 | * in the resulting stub has its activation id set to the |
| 75 | * activation id supplied as the second argument. |
| 76 | */ |
| 77 | public static Remote getStub(ActivationDesc desc, ActivationID id) |
| 78 | throws StubNotFoundException |
| 79 | { |
| 80 | String className = desc.getClassName(); |
| 81 | |
| 82 | try { |
| 83 | Class cl = |
| 84 | RMIClassLoader.loadClass(desc.getLocation(), className); |
| 85 | RemoteRef clientRef = new ActivatableRef(id, null); |
| 86 | return Util.createProxy(cl, clientRef, false); |
| 87 | |
| 88 | } catch (IllegalArgumentException e) { |
| 89 | throw new StubNotFoundException( |
| 90 | "class implements an illegal remote interface", e); |
| 91 | |
| 92 | } catch (ClassNotFoundException e) { |
| 93 | throw new StubNotFoundException("unable to load class: " + |
| 94 | className, e); |
| 95 | } catch (MalformedURLException e) { |
| 96 | throw new StubNotFoundException("malformed URL", e); |
| 97 | } |
| 98 | } |
| 99 | |
| 100 | /** |
| 101 | * Invoke method on remote object. This method delegates remote |
| 102 | * method invocation to the underlying ref type. If the |
| 103 | * underlying reference is not known (is null), then the object |
| 104 | * must be activated first. If an attempt at method invocation |
| 105 | * fails, the object should force reactivation. Method invocation |
| 106 | * must preserve "at most once" call semantics. In RMI, "at most |
| 107 | * once" applies to parameter deserialization at the remote site |
| 108 | * and the remote object's method execution. "At most once" does |
| 109 | * not apply to parameter serialization at the client so the |
| 110 | * parameters of a call don't need to be buffered in anticipation |
| 111 | * of call retry. Thus, a method call is only be retried if the |
| 112 | * initial method invocation does not execute at all at the server |
| 113 | * (including parameter deserialization). |
| 114 | */ |
| 115 | public Object invoke(Remote obj, |
| 116 | java.lang.reflect.Method method, |
| 117 | Object[] params, |
| 118 | long opnum) |
| 119 | throws Exception |
| 120 | { |
| 121 | |
| 122 | boolean force = false; |
| 123 | RemoteRef localRef; |
| 124 | Exception exception = null; |
| 125 | |
| 126 | /* |
| 127 | * Attempt object activation if active ref is unknown. |
| 128 | * Throws a RemoteException if object can't be activated. |
| 129 | */ |
| 130 | synchronized (this) { |
| 131 | if (ref == null) { |
| 132 | localRef = activate(force); |
| 133 | force = true; |
| 134 | } else { |
| 135 | localRef = ref; |
| 136 | } |
| 137 | } |
| 138 | |
| 139 | for (int retries = MAX_RETRIES; retries > 0; retries--) { |
| 140 | |
| 141 | try { |
| 142 | return localRef.invoke(obj, method, params, opnum); |
| 143 | } catch (NoSuchObjectException e) { |
| 144 | /* |
| 145 | * Object is not active in VM; retry call |
| 146 | */ |
| 147 | exception = e; |
| 148 | } catch (ConnectException e) { |
| 149 | /* |
| 150 | * Failure during connection setup; retry call |
| 151 | */ |
| 152 | exception = e; |
| 153 | } catch (UnknownHostException e) { |
| 154 | /* |
| 155 | * Failure during connection setup; retry call. |
| 156 | */ |
| 157 | exception = e; |
| 158 | } catch (ConnectIOException e) { |
| 159 | /* |
| 160 | * Failure setting up multiplexed connection or reusing |
| 161 | * cached connection; retry call |
| 162 | */ |
| 163 | exception = e; |
| 164 | } catch (MarshalException e) { |
| 165 | /* |
| 166 | * Failure during parameter serialization; call may |
| 167 | * have reached server, so call retry not possible. |
| 168 | */ |
| 169 | throw e; |
| 170 | } catch (ServerError e) { |
| 171 | /* |
| 172 | * Call reached server; propagate remote exception. |
| 173 | */ |
| 174 | throw e; |
| 175 | } catch (ServerException e) { |
| 176 | /* |
| 177 | * Call reached server; propagate remote exception |
| 178 | */ |
| 179 | throw e; |
| 180 | } catch (RemoteException e) { |
| 181 | /* |
| 182 | * This is a catch-all for other RemoteExceptions. |
| 183 | * UnmarshalException being the only one relevant. |
| 184 | * |
| 185 | * StubNotFoundException should never show up because |
| 186 | * it is generally thrown when attempting to locate |
| 187 | * a stub. |
| 188 | * |
| 189 | * UnexpectedException should never show up because |
| 190 | * it is only thrown by a stub and would be wrapped |
| 191 | * in a ServerException if it was propagated by a |
| 192 | * remote call. |
| 193 | */ |
| 194 | synchronized (this) { |
| 195 | if (localRef == ref) { |
| 196 | ref = null; // this may be overly conservative |
| 197 | } |
| 198 | } |
| 199 | |
| 200 | throw e; |
| 201 | } |
| 202 | |
| 203 | if (retries > 1) { |
| 204 | /* |
| 205 | * Activate object, since object could not be reached. |
| 206 | */ |
| 207 | synchronized (this) { |
| 208 | if (localRef.remoteEquals(ref) || ref == null) { |
| 209 | RemoteRef newRef = activate(force); |
| 210 | |
| 211 | if (newRef.remoteEquals(localRef) && |
| 212 | exception instanceof NoSuchObjectException && |
| 213 | force == false) { |
| 214 | /* |
| 215 | * If last exception was NoSuchObjectException, |
| 216 | * then old value of ref is definitely wrong, |
| 217 | * so make sure that it is different. |
| 218 | */ |
| 219 | newRef = activate(true); |
| 220 | } |
| 221 | |
| 222 | localRef = newRef; |
| 223 | force = true; |
| 224 | } else { |
| 225 | localRef = ref; |
| 226 | force = false; |
| 227 | } |
| 228 | } |
| 229 | } |
| 230 | } |
| 231 | |
| 232 | /* |
| 233 | * Retries unsuccessful, so throw last exception |
| 234 | */ |
| 235 | throw exception; |
| 236 | } |
| 237 | |
| 238 | /** |
| 239 | * private method to obtain the ref for a call. |
| 240 | */ |
| 241 | private synchronized RemoteRef getRef() |
| 242 | throws RemoteException |
| 243 | { |
| 244 | if (ref == null) { |
| 245 | ref = activate(false); |
| 246 | } |
| 247 | |
| 248 | return ref; |
| 249 | } |
| 250 | |
| 251 | /** |
| 252 | * private method to activate the remote object. |
| 253 | * |
| 254 | * NOTE: the caller must be synchronized on "this" before |
| 255 | * calling this method. |
| 256 | */ |
| 257 | private RemoteRef activate(boolean force) |
| 258 | throws RemoteException |
| 259 | { |
| 260 | assert Thread.holdsLock(this); |
| 261 | |
| 262 | ref = null; |
| 263 | try { |
| 264 | /* |
| 265 | * Activate the object and retrieve the remote reference |
| 266 | * from inside the stub returned as the result. Then |
| 267 | * set this activatable ref's internal ref to be the |
| 268 | * ref inside the ref of the stub. In more clear terms, |
| 269 | * the stub returned from the activate call contains an |
| 270 | * ActivatableRef. We need to set the ref in *this* |
| 271 | * ActivatableRef to the ref inside the ActivatableRef |
| 272 | * retrieved from the stub. The ref type embedded in the |
| 273 | * ActivatableRef is typically a UnicastRef. |
| 274 | */ |
| 275 | |
| 276 | Remote proxy = id.activate(force); |
| 277 | ActivatableRef newRef = null; |
| 278 | |
| 279 | if (proxy instanceof RemoteStub) { |
| 280 | newRef = (ActivatableRef) ((RemoteStub) proxy).getRef(); |
| 281 | } else { |
| 282 | /* |
| 283 | * Assume that proxy is an instance of a dynamic proxy |
| 284 | * class. If that assumption is not correct, or either of |
| 285 | * the casts below fails, the resulting exception will be |
| 286 | * wrapped in an ActivateFailedException below. |
| 287 | */ |
| 288 | RemoteObjectInvocationHandler handler = |
| 289 | (RemoteObjectInvocationHandler) |
| 290 | Proxy.getInvocationHandler(proxy); |
| 291 | newRef = (ActivatableRef) handler.getRef(); |
| 292 | } |
| 293 | ref = newRef.ref; |
| 294 | return ref; |
| 295 | |
| 296 | } catch (ConnectException e) { |
| 297 | throw new ConnectException("activation failed", e); |
| 298 | } catch (RemoteException e) { |
| 299 | throw new ConnectIOException("activation failed", e); |
| 300 | } catch (UnknownObjectException e) { |
| 301 | throw new NoSuchObjectException("object not registered"); |
| 302 | } catch (ActivationException e) { |
| 303 | throw new ActivateFailedException("activation failed", e); |
| 304 | } |
| 305 | } |
| 306 | |
| 307 | /** |
| 308 | * This call is used by the old 1.1 stub protocol and is |
| 309 | * unsupported since activation requires 1.2 stubs. |
| 310 | */ |
| 311 | public synchronized RemoteCall newCall(RemoteObject obj, |
| 312 | Operation[] ops, |
| 313 | int opnum, |
| 314 | long hash) |
| 315 | throws RemoteException |
| 316 | { |
| 317 | throw new UnsupportedOperationException(versionComplaint); |
| 318 | } |
| 319 | |
| 320 | /** |
| 321 | * This call is used by the old 1.1 stub protocol and is |
| 322 | * unsupported since activation requires 1.2 stubs. |
| 323 | */ |
| 324 | public void invoke(RemoteCall call) throws Exception |
| 325 | { |
| 326 | throw new UnsupportedOperationException(versionComplaint); |
| 327 | } |
| 328 | |
| 329 | /** |
| 330 | * This call is used by the old 1.1 stub protocol and is |
| 331 | * unsupported since activation requires 1.2 stubs. |
| 332 | */ |
| 333 | public void done(RemoteCall call) throws RemoteException { |
| 334 | throw new UnsupportedOperationException(versionComplaint); |
| 335 | } |
| 336 | |
| 337 | /** |
| 338 | * Returns the class of the ref type to be serialized |
| 339 | */ |
| 340 | public String getRefClass(ObjectOutput out) |
| 341 | { |
| 342 | return "ActivatableRef"; |
| 343 | } |
| 344 | |
| 345 | /** |
| 346 | * Write out external representation for remote ref. |
| 347 | */ |
| 348 | public void writeExternal(ObjectOutput out) throws IOException |
| 349 | { |
| 350 | RemoteRef localRef = ref; |
| 351 | |
| 352 | out.writeObject(id); |
| 353 | if (localRef == null) { |
| 354 | out.writeUTF(""); |
| 355 | } else { |
| 356 | out.writeUTF(localRef.getRefClass(out)); |
| 357 | localRef.writeExternal(out); |
| 358 | } |
| 359 | } |
| 360 | |
| 361 | /** |
| 362 | * Read in external representation for remote ref. |
| 363 | * @exception ClassNotFoundException If the class for an object |
| 364 | * being restored cannot be found. |
| 365 | */ |
| 366 | public void readExternal(ObjectInput in) |
| 367 | throws IOException, ClassNotFoundException |
| 368 | { |
| 369 | id = (ActivationID)in.readObject(); |
| 370 | ref = null; |
| 371 | String className = in.readUTF(); |
| 372 | |
| 373 | if (className.equals("")) return; |
| 374 | |
| 375 | try { |
| 376 | Class refClass = Class.forName(RemoteRef.packagePrefix + "." + |
| 377 | className); |
| 378 | ref = (RemoteRef)refClass.newInstance(); |
| 379 | ref.readExternal(in); |
| 380 | } catch (InstantiationException e) { |
| 381 | throw new UnmarshalException("Unable to create remote reference", |
| 382 | e); |
| 383 | } catch (IllegalAccessException e) { |
| 384 | throw new UnmarshalException("Illegal access creating remote reference"); |
| 385 | } |
| 386 | } |
| 387 | |
| 388 | //----------------------------------------------------------------------; |
| 389 | /** |
| 390 | * Method from object, forward from RemoteObject |
| 391 | */ |
| 392 | public String remoteToString() { |
| 393 | return Util.getUnqualifiedName(getClass()) + |
| 394 | " [remoteRef: " + ref + "]"; |
| 395 | } |
| 396 | |
| 397 | /** |
| 398 | * default implementation of hashCode for remote objects |
| 399 | */ |
| 400 | public int remoteHashCode() { |
| 401 | return id.hashCode(); |
| 402 | } |
| 403 | |
| 404 | /** default implementation of equals for remote objects |
| 405 | */ |
| 406 | public boolean remoteEquals(RemoteRef ref) { |
| 407 | if (ref instanceof ActivatableRef) |
| 408 | return id.equals(((ActivatableRef)ref).id); |
| 409 | return false; |
| 410 | } |
| 411 | } |