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 }