libjava/classpath/java/rmi/server/RemoteObject.java

   1 /* RemoteObject.java --
   2    Copyright (c) 1996, 1997, 1998, 1999, 2004  Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package java.rmi.server;
  39
  40 import java.io.IOException;
  41 import java.io.ObjectInputStream;
  42 import java.io.ObjectOutput;
  43 import java.io.ObjectOutputStream;
  44 import java.io.Serializable;
  45 import java.rmi.NoSuchObjectException;
  46 import java.rmi.Remote;
  47 import java.rmi.UnmarshalException;
  48 import java.util.WeakHashMap;
  49
  50 public abstract class RemoteObject
  51         implements Remote, Serializable {
  52
  53 private static final long serialVersionUID = -3215090123894869218l;
  54
  55 protected transient RemoteRef ref;
  56
  57 private static final WeakHashMap stubs = new WeakHashMap();
  58
  59 protected RemoteObject() {
  60         this(null);
  61 }
  62
  63 protected RemoteObject(RemoteRef newref) {
  64         ref = newref;
  65 }
  66
  67 public RemoteRef getRef() {
  68         return (ref);
  69 }
  70
  71 synchronized static void addStub(Remote obj, Remote stub)
  72 {
  73   stubs.put(obj, stub);
  74 }
  75
  76 synchronized static void deleteStub(Remote obj)
  77 {
  78   stubs.remove(obj);
  79 }
  80
  81   public static Remote toStub(Remote obj) throws NoSuchObjectException
  82   {
  83     Remote stub = (Remote)stubs.get(obj);
  84
  85     if (stub == null)
  86       throw new NoSuchObjectException(obj.getClass().getName());
  87
  88     return stub;
  89   }
  90
  91 public int hashCode() {
  92         if (ref == null) {
  93                 return (0);
  94         }
  95         else {
  96                 return (ref.hashCode());
  97         }
  98 }
  99
 100 public boolean equals(Object obj) {
 101         // We only compare references.
 102         return (this == obj);
 103 }
 104
 105 /**
 106  * Get the string representation of this remote object.
 107  */
 108   public String toString()
 109   {
 110     if (ref == null)
 111       return getClass ().toString ();
 112     return (ref.toString ());
 113   }
 114
 115   /**
 116    * Read the remote object from the input stream. Expects the class name
 117    * without package first. Then the method creates and assigns the {@link #ref}
 118    * an instance of this class and calls its .readExternal method. The standard
 119    * packageless class names are UnicastRef, UnicastRef2, UnicastServerRef,
 120    * UnicastServerRef2, ActivatableRef or ActivatableServerRef.
 121    *
 122    * @param in the stream to read from
 123    * @throws IOException if the IO exception occurs
 124    * @throws ClassNotFoundException if the class with the given name is not
 125    *           present in the package gnu.java.rmi.server (for the case of the
 126    *           GNU Classpath.
 127    */
 128   private void readObject(ObjectInputStream in) throws IOException,
 129       ClassNotFoundException
 130   {
 131     String cname = in.readUTF();
 132     if (! cname.equals(""))
 133       {
 134         if (cname.equals("UnicastRef2"))
 135           {
 136             // hack for interoperating with JDK
 137             cname = "UnicastRef";
 138             in.read(); // some unknown UnicastRef2 field
 139           }
 140
 141         // It would be nice to use RemoteRef.packagePrefix here, but for binary
 142         // compatibility with the JDK that has to contain "sun.rmi.server"...
 143         cname = "gnu.java.rmi.server." + cname;
 144         try
 145           {
 146             Class cls = Class.forName(cname);
 147             ref = (RemoteRef) cls.newInstance();
 148           }
 149         catch (InstantiationException e1)
 150           {
 151             throw new UnmarshalException("failed to create ref", e1);
 152           }
 153         catch (IllegalAccessException e2)
 154           {
 155             throw new UnmarshalException("failed to create ref", e2);
 156           }
 157         ref.readExternal(in);
 158       }
 159     else
 160       {
 161         ref = (RemoteRef) in.readObject();
 162       }
 163   }
 164
 165   /**
 166    * Write the remote object to the output stream. This method first calls
 167    * {@link RemoteRef#getRefClass(ObjectOutput)} on the {@link #ref} to get the
 168    * class name without package, writes this name and then calls the
 169    * ref.writeObject to write the data. The standard packageless class names are
 170    * UnicastRef, UnicastRef2, UnicastServerRef, UnicastServerRef2,
 171    * ActivatableRef or ActivatableServerRef. The empty string with the
 172    * subsequently following serialized ref instance be written if the
 173    * ref.getRefClass returns null.
 174    *
 175    * @param out the stream to write to
 176    * @throws IOException if one occurs during writing
 177    * @throws ClassNotFoundException never in this implementation (specified as
 178    *           part of the API standard)
 179    * @throws UnmarshalException if the remote reference of this remote object is
 180    *           null.
 181    */
 182   private void writeObject(ObjectOutputStream out) throws IOException,
 183       ClassNotFoundException
 184   {
 185     if (ref == null)
 186       {
 187         throw new UnmarshalException("no ref to serialize");
 188       }
 189     String cname = ref.getRefClass(out);
 190     if (cname != null && cname.length() > 0)
 191       {
 192         out.writeUTF(cname);
 193         ref.writeExternal(out);
 194       }
 195     else
 196       {
 197         out.writeUTF("");
 198         out.writeObject(ref);
 199       }
 200   }
 201
 202 }