001    /* Stub.java --
002       Copyright (C) 2004, 2004, 2005 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    
039    package javax.rmi.CORBA;
040    
041    import gnu.javax.rmi.CORBA.DelegateFactory;
042    import gnu.javax.rmi.CORBA.StubDelegateImpl;
043    
044    import java.io.IOException;
045    import java.io.ObjectInputStream;
046    import java.io.ObjectOutputStream;
047    import java.io.Serializable;
048    import java.rmi.RemoteException;
049    
050    import javax.rmi.PortableRemoteObject;
051    
052    import org.omg.CORBA.ORB;
053    import org.omg.CORBA_2_3.portable.ObjectImpl;
054    
055    /**
056     * A Stub descendants provide access to the object on the client side. This base
057     * class implements methods, required for remote or local invocation using CORBA
058     * mechanisms. The most of the functionality is forwarded to the stub delegate.
059     * This delegate can be altered by setting the system property
060     * "javax.rmi.CORBA.StubClass" to the name of the alternative class that must
061     * implement {@link StubDelegate}. Hence Stub contains two delegates, one for
062     * Stub-related operations and another inherited from the ObjectImpl.
063     * 
064     * @specnote GNU Classpath uses separate delegate per each Stub. The delegate
065     * holds information about the ORB and other data, specific for the each Stub.
066     * 
067     * @author Audrius Meskauskas (AudriusA@Bioinformatics.org)
068     */
069    public abstract class Stub
070      extends ObjectImpl
071      implements Serializable
072    {
073      /**
074       * For compatability with Sun's JDK 1.4.2 rev. 5
075       */
076      private static final long serialVersionUID = 1087775603798577179L;
077    
078      /**
079       * The hashcode, computed once (expensive operation).
080       */
081      transient int m_hash = Integer.MIN_VALUE;
082    
083      /**
084       * The stringified reference, computed once (expensive operation).
085       */
086      transient String m_ior;
087    
088      /**
089       * The ORB, where the stub is connected on the client side.
090       */
091      transient ORB m_orb;
092    
093      /**
094       * The associated delegate, responsible for the major of the functionality of
095       * this stub.
096       */
097      static StubDelegate delegate = (StubDelegate) DelegateFactory.getInstance(DelegateFactory.STUB);
098    
099      /**
100       * Returns the same hashcode for all stubs that point to the same remote
101       * object.
102       */
103      public int hashCode()
104      {
105        if (m_hash == Integer.MIN_VALUE)
106          m_hash = delegate.hashCode(this);
107        // This should finally result to the IOR comparison.
108        return m_hash;
109      }
110    
111      /**
112       * The stubs are equal if they point to the same remote object.
113       */
114      public boolean equals(java.lang.Object obj)
115      {
116        return delegate.equals(this, obj);
117      }
118    
119      /**
120       * Get the string representation of this Stub.
121       * 
122       * @return the CORBA IOR reference.
123       */
124      public String toString()
125      {
126        if (m_ior == null)
127          m_ior = delegate.toString(this);
128        return m_ior;
129      }
130    
131      /**
132       * <p>
133       * Finds the suitable {@link Tie} for this Stub and connects it to the given
134       * ORB. The tie is found by the name pattern. If the found tie is derived from
135       * {@link org.omg.CORBA.PortableServer.Servant}, it is connected to the root
136       * POA, also activating it (if not already active).
137       * </p>
138       * <p>
139       * This method does not allow to specify, to which POA the found Tie must be
140       * connected and requires to use the deprecated method {@link ORB#connect}.
141       * Many useful POA features remain unaccessible. A better alternative it might
142       * be to generate a {@link org.omg.CORBA.PortableServer.Servant} - derived Tie
143       * (-poa key in rmic) and connect it to POA in one of the many ways, listed in
144       * the description of the {@link orb.omg.PortableServer} package). The
145       * obtained CORBA object can be narrowed into stub using
146       * {@link PortableRemoteObject#narrow}.
147       * </p>
148       * <p>
149       * It is frequently easier to call {@link PortableRemoteObject#connect} rather
150       * than this method.
151       * </p>
152       * 
153       * @param orb the ORB where the Stub must be connected.
154       * 
155       * @throws RemoteException if the stub is already connected to some other ORB.
156       * If the stub is already connected to the ORB that was passed as parameter,
157       * the method returns without action.
158       * 
159       * @throws BAD_PARAM if the name of this stub does not match the stub name
160       * pattern, "_*_Stub" or if the Tie class, "_*Impl_Tie", does not exists or an
161       * instance of this class cannot be instantiated.
162       */
163      public void connect(ORB orb)
164        throws RemoteException
165      {
166        if (m_orb != null && orb != null)
167          {
168            if (m_orb.equals(orb))
169              throw new RemoteException("Stub " + this
170                + " is connected to another ORB, " + orb);
171            else
172              return;
173          }
174        m_orb = orb;
175        delegate.connect(this, orb);
176      }
177    
178      /**
179       * Required by serialized form of Java API doc.
180       */
181      private void readObject(ObjectInputStream input)
182        throws IOException, ClassNotFoundException
183      {
184        if (delegate instanceof StubDelegateImpl)
185          ((StubDelegateImpl) delegate).readObject(this, input, m_orb);
186        else
187          delegate.readObject(this, input);
188      }
189    
190      /**
191       * Required by serialized form of Java API doc.
192       */
193      private void writeObject(ObjectOutputStream output)
194        throws IOException
195      {
196        // The m_orb in this case may be either known or not.
197        if (delegate instanceof StubDelegateImpl)
198          ((StubDelegateImpl) delegate).writeObject(this, output, m_orb);
199        else
200    
201          delegate.writeObject(this, output);
202      }
203    }