1 /*
   2  * Copyright (c) 1996, 2014, 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 java.rmi.server;
  27 
  28 import java.rmi.Remote;
  29 import java.rmi.NoSuchObjectException;
  30 import java.lang.reflect.Proxy;
  31 import sun.rmi.server.Util;
  32 
  33 /**
  34  * The <code>RemoteObject</code> class implements the
  35  * <code>java.lang.Object</code> behavior for remote objects.
  36  * <code>RemoteObject</code> provides the remote semantics of Object by
  37  * implementing methods for hashCode, equals, and toString.
  38  *
  39  * @author      Ann Wollrath
  40  * @author      Laird Dornin
  41  * @author      Peter Jones
  42  * @since       1.1
  43  */
  44 public abstract class RemoteObject implements Remote, java.io.Serializable {
  45 
  46     /** The object's remote reference. */
  47     transient protected RemoteRef ref;
  48 
  49     /** indicate compatibility with JDK 1.1.x version of class */
  50     private static final long serialVersionUID = -3215090123894869218L;
  51 
  52     /**
  53      * Creates a remote object.
  54      */
  55     protected RemoteObject() {
  56         ref = null;
  57     }
  58 
  59     /**
  60      * Creates a remote object, initialized with the specified remote
  61      * reference.
  62      * @param newref remote reference
  63      */
  64     protected RemoteObject(RemoteRef newref) {
  65         ref = newref;
  66     }
  67 
  68     /**
  69      * Returns the remote reference for the remote object.
  70      *
  71      * <p>Note: The object returned from this method may be an instance of
  72      * an implementation-specific class.  The <code>RemoteObject</code>
  73      * class ensures serialization portability of its instances' remote
  74      * references through the behavior of its custom
  75      * <code>writeObject</code> and <code>readObject</code> methods.  An
  76      * instance of <code>RemoteRef</code> should not be serialized outside
  77      * of its <code>RemoteObject</code> wrapper instance or the result may
  78      * be unportable.
  79      *
  80      * @return remote reference for the remote object
  81      * @since 1.2
  82      */
  83     public RemoteRef getRef() {
  84         return ref;
  85     }
  86 
  87     /**
  88      * Returns the stub for the remote object <code>obj</code> passed
  89      * as a parameter. This operation is only valid <i>after</i>
  90      * the object has been exported.
  91      * @param obj the remote object whose stub is needed
  92      * @return the stub for the remote object, <code>obj</code>.
  93      * @exception NoSuchObjectException if the stub for the
  94      * remote object could not be found.
  95      * @since 1.2
  96      */
  97     @SuppressWarnings("deprecation")
  98     public static Remote toStub(Remote obj) throws NoSuchObjectException {
  99         if (obj instanceof RemoteStub ||
 100             (obj != null &&
 101              Proxy.isProxyClass(obj.getClass()) &&
 102              Proxy.getInvocationHandler(obj) instanceof
 103              RemoteObjectInvocationHandler))
 104         {
 105             return obj;
 106         } else {
 107             return sun.rmi.transport.ObjectTable.getStub(obj);
 108         }
 109     }
 110 
 111     /**
 112      * Returns a hashcode for a remote object.  Two remote object stubs
 113      * that refer to the same remote object will have the same hash code
 114      * (in order to support remote objects as keys in hash tables).
 115      *
 116      * @see             java.util.Hashtable
 117      */
 118     public int hashCode() {
 119         return (ref == null) ? super.hashCode() : ref.remoteHashCode();
 120     }
 121 
 122     /**
 123      * Compares two remote objects for equality.
 124      * Returns a boolean that indicates whether this remote object is
 125      * equivalent to the specified Object. This method is used when a
 126      * remote object is stored in a hashtable.
 127      * If the specified Object is not itself an instance of RemoteObject,
 128      * then this method delegates by returning the result of invoking the
 129      * <code>equals</code> method of its parameter with this remote object
 130      * as the argument.
 131      * @param   obj     the Object to compare with
 132      * @return  true if these Objects are equal; false otherwise.
 133      * @see             java.util.Hashtable
 134      */
 135     public boolean equals(Object obj) {
 136         if (obj instanceof RemoteObject) {
 137             if (ref == null) {
 138                 return obj == this;
 139             } else {
 140                 return ref.remoteEquals(((RemoteObject)obj).ref);
 141             }
 142         } else if (obj != null) {
 143             /*
 144              * Fix for 4099660: if object is not an instance of RemoteObject,
 145              * use the result of its equals method, to support symmetry is a
 146              * remote object implementation class that does not extend
 147              * RemoteObject wishes to support equality with its stub objects.
 148              */
 149             return obj.equals(this);
 150         } else {
 151             return false;
 152         }
 153     }
 154 
 155     /**
 156      * Returns a String that represents the value of this remote object.
 157      */
 158     public String toString() {
 159         String classname = Util.getUnqualifiedName(getClass());
 160         return (ref == null) ? classname :
 161             classname + "[" + ref.remoteToString() + "]";
 162     }
 163 
 164     /**
 165      * <code>writeObject</code> for custom serialization.
 166      *
 167      * <p>This method writes this object's serialized form for this class
 168      * as follows:
 169      *
 170      * <p>The {@link RemoteRef#getRefClass(java.io.ObjectOutput) getRefClass}
 171      * method is invoked on this object's <code>ref</code> field
 172      * to obtain its external ref type name.
 173      * If the value returned by <code>getRefClass</code> was
 174      * a non-<code>null</code> string of length greater than zero,
 175      * the <code>writeUTF</code> method is invoked on <code>out</code>
 176      * with the value returned by <code>getRefClass</code>, and then
 177      * the <code>writeExternal</code> method is invoked on
 178      * this object's <code>ref</code> field passing <code>out</code>
 179      * as the argument; otherwise,
 180      * the <code>writeUTF</code> method is invoked on <code>out</code>
 181      * with a zero-length string (<code>""</code>), and then
 182      * the <code>writeObject</code> method is invoked on <code>out</code>
 183      * passing this object's <code>ref</code> field as the argument.
 184      *
 185      * @serialData
 186      *
 187      * The serialized data for this class comprises a string (written with
 188      * <code>ObjectOutput.writeUTF</code>) that is either the external
 189      * ref type name of the contained <code>RemoteRef</code> instance
 190      * (the <code>ref</code> field) or a zero-length string, followed by
 191      * either the external form of the <code>ref</code> field as written by
 192      * its <code>writeExternal</code> method if the string was of non-zero
 193      * length, or the serialized form of the <code>ref</code> field as
 194      * written by passing it to the serialization stream's
 195      * <code>writeObject</code> if the string was of zero length.
 196      *
 197      * <p>If this object is an instance of
 198      * {@link RemoteStub} or {@link RemoteObjectInvocationHandler}
 199      * that was returned from any of
 200      * the <code>UnicastRemoteObject.exportObject</code> methods
 201      * and custom socket factories are not used,
 202      * the external ref type name is <code>"UnicastRef"</code>.
 203      *
 204      * If this object is an instance of
 205      * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>
 206      * that was returned from any of
 207      * the <code>UnicastRemoteObject.exportObject</code> methods
 208      * and custom socket factories are used,
 209      * the external ref type name is <code>"UnicastRef2"</code>.
 210      *
 211      * If this object is an instance of
 212      * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>
 213      * that was returned from any of
 214      * the <code>java.rmi.activation.Activatable.exportObject</code> methods,
 215      * the external ref type name is <code>"ActivatableRef"</code>.
 216      *
 217      * If this object is an instance of
 218      * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>
 219      * that was returned from
 220      * the <code>RemoteObject.toStub</code> method (and the argument passed
 221      * to <code>toStub</code> was not itself a <code>RemoteStub</code>),
 222      * the external ref type name is a function of how the remote object
 223      * passed to <code>toStub</code> was exported, as described above.
 224      *
 225      * If this object is an instance of
 226      * <code>RemoteStub</code> or <code>RemoteObjectInvocationHandler</code>
 227      * that was originally created via deserialization,
 228      * the external ref type name is the same as that which was read
 229      * when this object was deserialized.
 230      *
 231      * <p>If this object is an instance of
 232      * <code>java.rmi.server.UnicastRemoteObject</code> that does not
 233      * use custom socket factories,
 234      * the external ref type name is <code>"UnicastServerRef"</code>.
 235      *
 236      * If this object is an instance of
 237      * <code>UnicastRemoteObject</code> that does
 238      * use custom socket factories,
 239      * the external ref type name is <code>"UnicastServerRef2"</code>.
 240      *
 241      * <p>Following is the data that must be written by the
 242      * <code>writeExternal</code> method and read by the
 243      * <code>readExternal</code> method of <code>RemoteRef</code>
 244      * implementation classes that correspond to the each of the
 245      * defined external ref type names:
 246      *
 247      * <p>For <code>"UnicastRef"</code>:
 248      *
 249      * <ul>
 250      *
 251      * <li>the hostname of the referenced remote object,
 252      * written by {@link java.io.ObjectOutput#writeUTF(String)}
 253      *
 254      * <li>the port of the referenced remote object,
 255      * written by {@link java.io.ObjectOutput#writeInt(int)}
 256      *
 257      * <li>the data written as a result of calling
 258      * {link java.rmi.server.ObjID#write(java.io.ObjectOutput)}
 259      * on the <code>ObjID</code> instance contained in the reference
 260      *
 261      * <li>the boolean value <code>false</code>,
 262      * written by {@link java.io.ObjectOutput#writeBoolean(boolean)}
 263      *
 264      * </ul>
 265      *
 266      * <p>For <code>"UnicastRef2"</code> with a
 267      * <code>null</code> client socket factory:
 268      *
 269      * <ul>
 270      *
 271      * <li>the byte value <code>0x00</code>
 272      * (indicating <code>null</code> client socket factory),
 273      * written by {@link java.io.ObjectOutput#writeByte(int)}
 274      *
 275      * <li>the hostname of the referenced remote object,
 276      * written by {@link java.io.ObjectOutput#writeUTF(String)}
 277      *
 278      * <li>the port of the referenced remote object,
 279      * written by {@link java.io.ObjectOutput#writeInt(int)}
 280      *
 281      * <li>the data written as a result of calling
 282      * {link java.rmi.server.ObjID#write(java.io.ObjectOutput)}
 283      * on the <code>ObjID</code> instance contained in the reference
 284      *
 285      * <li>the boolean value <code>false</code>,
 286      * written by {@link java.io.ObjectOutput#writeBoolean(boolean)}
 287      *
 288      * </ul>
 289      *
 290      * <p>For <code>"UnicastRef2"</code> with a
 291      * non-<code>null</code> client socket factory:
 292      *
 293      * <ul>
 294      *
 295      * <li>the byte value <code>0x01</code>
 296      * (indicating non-<code>null</code> client socket factory),
 297      * written by {@link java.io.ObjectOutput#writeByte(int)}
 298      *
 299      * <li>the hostname of the referenced remote object,
 300      * written by {@link java.io.ObjectOutput#writeUTF(String)}
 301      *
 302      * <li>the port of the referenced remote object,
 303      * written by {@link java.io.ObjectOutput#writeInt(int)}
 304      *
 305      * <li>a client socket factory (object of type
 306      * <code>java.rmi.server.RMIClientSocketFactory</code>),
 307      * written by passing it to an invocation of
 308      * <code>writeObject</code> on the stream instance
 309      *
 310      * <li>the data written as a result of calling
 311      * {link java.rmi.server.ObjID#write(java.io.ObjectOutput)}
 312      * on the <code>ObjID</code> instance contained in the reference
 313      *
 314      * <li>the boolean value <code>false</code>,
 315      * written by {@link java.io.ObjectOutput#writeBoolean(boolean)}
 316      *
 317      * </ul>
 318      *
 319      * <p>For <code>"ActivatableRef"</code> with a
 320      * <code>null</code> nested remote reference:
 321      *
 322      * <ul>
 323      *
 324      * <li>an instance of
 325      * <code>java.rmi.activation.ActivationID</code>,
 326      * written by passing it to an invocation of
 327      * <code>writeObject</code> on the stream instance
 328      *
 329      * <li>a zero-length string (<code>""</code>),
 330      * written by {@link java.io.ObjectOutput#writeUTF(String)}
 331      *
 332      * </ul>
 333      *
 334      * <p>For <code>"ActivatableRef"</code> with a
 335      * non-<code>null</code> nested remote reference:
 336      *
 337      * <ul>
 338      *
 339      * <li>an instance of
 340      * <code>java.rmi.activation.ActivationID</code>,
 341      * written by passing it to an invocation of
 342      * <code>writeObject</code> on the stream instance
 343      *
 344      * <li>the external ref type name of the nested remote reference,
 345      * which must be <code>"UnicastRef2"</code>,
 346      * written by {@link java.io.ObjectOutput#writeUTF(String)}
 347      *
 348      * <li>the external form of the nested remote reference,
 349      * written by invoking its <code>writeExternal</code> method
 350      * with the stream instance
 351      * (see the description of the external form for
 352      * <code>"UnicastRef2"</code> above)
 353      *
 354      * </ul>
 355      *
 356      * <p>For <code>"UnicastServerRef"</code> and
 357      * <code>"UnicastServerRef2"</code>, no data is written by the
 358      * <code>writeExternal</code> method or read by the
 359      * <code>readExternal</code> method.
 360      */
 361     private void writeObject(java.io.ObjectOutputStream out)
 362         throws java.io.IOException, java.lang.ClassNotFoundException
 363     {
 364         if (ref == null) {
 365             throw new java.rmi.MarshalException("Invalid remote object");
 366         } else {
 367             String refClassName = ref.getRefClass(out);
 368             if (refClassName == null || refClassName.length() == 0) {
 369                 /*
 370                  * No reference class name specified, so serialize
 371                  * remote reference.
 372                  */
 373                 out.writeUTF("");
 374                 out.writeObject(ref);
 375             } else {
 376                 /*
 377                  * Built-in reference class specified, so delegate
 378                  * to reference to write out its external form.
 379                  */
 380                 out.writeUTF(refClassName);
 381                 ref.writeExternal(out);
 382             }
 383         }
 384     }
 385 
 386     /**
 387      * <code>readObject</code> for custom serialization.
 388      *
 389      * <p>This method reads this object's serialized form for this class
 390      * as follows:
 391      *
 392      * <p>The <code>readUTF</code> method is invoked on <code>in</code>
 393      * to read the external ref type name for the <code>RemoteRef</code>
 394      * instance to be filled in to this object's <code>ref</code> field.
 395      * If the string returned by <code>readUTF</code> has length zero,
 396      * the <code>readObject</code> method is invoked on <code>in</code>,
 397      * and than the value returned by <code>readObject</code> is cast to
 398      * <code>RemoteRef</code> and this object's <code>ref</code> field is
 399      * set to that value.
 400      * Otherwise, this object's <code>ref</code> field is set to a
 401      * <code>RemoteRef</code> instance that is created of an
 402      * implementation-specific class corresponding to the external ref
 403      * type name returned by <code>readUTF</code>, and then
 404      * the <code>readExternal</code> method is invoked on
 405      * this object's <code>ref</code> field.
 406      *
 407      * <p>If the external ref type name is
 408      * <code>"UnicastRef"</code>, <code>"UnicastServerRef"</code>,
 409      * <code>"UnicastRef2"</code>, <code>"UnicastServerRef2"</code>,
 410      * or <code>"ActivatableRef"</code>, a corresponding
 411      * implementation-specific class must be found, and its
 412      * <code>readExternal</code> method must read the serial data
 413      * for that external ref type name as specified to be written
 414      * in the <b>serialData</b> documentation for this class.
 415      * If the external ref type name is any other string (of non-zero
 416      * length), a <code>ClassNotFoundException</code> will be thrown,
 417      * unless the implementation provides an implementation-specific
 418      * class corresponding to that external ref type name, in which
 419      * case this object's <code>ref</code> field will be set to an
 420      * instance of that implementation-specific class.
 421      */
 422     private void readObject(java.io.ObjectInputStream in)
 423         throws java.io.IOException, java.lang.ClassNotFoundException
 424     {
 425         String refClassName = in.readUTF();
 426         if (refClassName == null || refClassName.length() == 0) {
 427             /*
 428              * No reference class name specified, so construct
 429              * remote reference from its serialized form.
 430              */
 431             ref = (RemoteRef) in.readObject();
 432         } else {
 433             /*
 434              * Built-in reference class specified, so delegate to
 435              * internal reference class to initialize its fields from
 436              * its external form.
 437              */
 438             String internalRefClassName =
 439                 RemoteRef.packagePrefix + "." + refClassName;
 440             Class<?> refClass = Class.forName(internalRefClassName);
 441             try {
 442                 @SuppressWarnings("deprecation")
 443                 Object tmp = refClass.newInstance();
 444                 ref = (RemoteRef) tmp;
 445 
 446                 /*
 447                  * If this step fails, assume we found an internal
 448                  * class that is not meant to be a serializable ref
 449                  * type.
 450                  */
 451             } catch (InstantiationException | IllegalAccessException | ClassCastException e) {
 452                 throw new ClassNotFoundException(internalRefClassName, e);
 453             }
 454             ref.readExternal(in);
 455         }
 456     }
 457 }
--- EOF ---