001    /* RemoteObject.java --
002       Copyright (c) 1996, 1997, 1998, 1999, 2004  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    package java.rmi.server;
039    
040    import java.io.IOException;
041    import java.io.ObjectInputStream;
042    import java.io.ObjectOutput;
043    import java.io.ObjectOutputStream;
044    import java.io.Serializable;
045    import java.rmi.NoSuchObjectException;
046    import java.rmi.Remote;
047    import java.rmi.UnmarshalException;
048    import java.util.WeakHashMap;
049    
050    public abstract class RemoteObject
051            implements Remote, Serializable {
052    
053    private static final long serialVersionUID = -3215090123894869218l;
054    
055    protected transient RemoteRef ref;
056    
057    private static final WeakHashMap stubs = new WeakHashMap();
058    
059    protected RemoteObject() {
060            this(null);
061    }
062    
063    protected RemoteObject(RemoteRef newref) {
064            ref = newref;
065    }
066    
067    public RemoteRef getRef() {
068            return (ref);
069    }
070    
071    synchronized static void addStub(Remote obj, Remote stub)
072    {
073      stubs.put(obj, stub);
074    }
075    
076    synchronized static void deleteStub(Remote obj)
077    {
078      stubs.remove(obj);
079    }
080    
081      public static Remote toStub(Remote obj) throws NoSuchObjectException 
082      {
083        Remote stub = (Remote)stubs.get(obj);
084    
085        if (stub == null)
086          throw new NoSuchObjectException(obj.getClass().getName());
087    
088        return stub;
089      }
090    
091    public int hashCode() {
092            if (ref == null) {
093                    return (0);
094            }
095            else {
096                    return (ref.hashCode());
097            }
098    }
099    
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    }