Source for java.rmi.server.RemoteObject

   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: }