001/* PortableRemoteObject.java --
002   Copyright (C) 2004, 2004, 2005 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038
039package javax.rmi;
040
041import gnu.javax.rmi.CORBA.DelegateFactory;
042
043import org.omg.CORBA.BAD_PARAM;
044import org.omg.CORBA.ORB;
045import org.omg.CORBA.portable.ObjectImpl;
046import org.omg.PortableServer.POA;
047import org.omg.PortableServer.Servant;
048
049import java.rmi.NoSuchObjectException;
050import java.rmi.Remote;
051import java.rmi.RemoteException;
052
053import javax.rmi.CORBA.PortableRemoteObjectDelegate;
054import javax.rmi.CORBA.Stub;
055import javax.rmi.CORBA.Tie;
056import javax.rmi.CORBA.Util;
057
058/**
059 * <p>
060 * An utility class for RMI/IDL server side object implementations. Server side
061 * implementation objects may inherit from this class, but this is not
062 * mandatory, as the needed methds are static. Server side implementations may
063 * choose to inherit from {@link ObjectImpl} or {@link Servant} instead.
064 * </p>
065 * <p>
066 * The functionality of methods in this class is forwarded to the enclosed
067 * PortableRemoteObjectDelegate. This delegate can be altered by setting the
068 * system property "javax.rmi.CORBA.PortableRemoteObjectClass" to the name of
069 * the alternative class that must implement
070 * {@link PortableRemoteObjectDelegate}.
071 * </p>
072 *
073 * @author Audrius Meskauskas (AudriusA@Bioinformatics.org)
074 */
075public class PortableRemoteObject
076{
077  /**
078   * A delegate where the functionality is forwarded.
079   */
080  static PortableRemoteObjectDelegate delegate = (PortableRemoteObjectDelegate) DelegateFactory.getInstance(DelegateFactory.PORTABLE_REMOTE_OBJECT);
081
082  /**
083   * The protected constructor calls {@link exportObject} (this).
084   *
085   * @throws RemoteException if the exportObject(this) throws one.
086   */
087  protected PortableRemoteObject()
088    throws RemoteException
089  {
090    exportObject((Remote) this);
091  }
092
093  /**
094   * <p>
095   * Makes the remote object <code>a_target</code> ready for remote
096   * communication using the same communications runtime as for the passed
097   * <code>a_source</code> parameter. The a_target is connected to the same
098   * ORB (and, if applicable, to the same {@link POA}) as the a_source.
099   *
100   * @param target the target to connect to ORB, must be an instance of either
101   * {@link ObjectImpl} (Stubs and old-style ties) or {@link Tie}.
102   *
103   * @param source the object, providing the connection information, must be
104   * an instance of either {@link ObjectImpl} (Stubs and old-style ties) or
105   * {@link Servant} (the next-generation Ties supporting {@link POA}).
106   *
107   * @throws RemoteException if the target is already connected to another ORB.
108   */
109  public static void connect(Remote target, Remote source)
110    throws RemoteException
111  {
112    delegate.connect(target, source);
113  }
114
115  /**
116   * <p>
117   * Makes a server object ready for remote calls. The subclasses of
118   * PortableRemoteObject do not need to call this method, as it is called by
119   * the constructor.
120   * </p>
121   * <p>
122   * This method only creates a tie object and caches it for future usage. The
123   * created tie does not have a delegate or an ORB associated.
124   * </p>
125   *
126   * @param object the object to export.
127   *
128   * @throws RemoteException if export fails due any reason.
129   */
130  public static void exportObject(Remote object)
131    throws RemoteException
132  {
133    delegate.exportObject(object);
134  }
135
136  /**
137   * Narrows the passed object to conform to the given interface or IDL type. In
138   * RMI-IIOP, this method replaces the narrow(org.omg.CORBA.Object) method that
139   * was present in the CORBA Helpers. This method frequently returns different
140   * instance and cannot be replaced by the direct cast. The typical narrowing
141   * cases (all supported by GNU Classpath) are:
142   * <ul>
143   * <li>A CORBA object (for instance, returned by the
144   * {@link ORB#string_to_object} or from the naming service) can be narrowed
145   * into interface, derived from Remote. The method will try to locate an
146   * appropriate {@link Stub} by the name pattern (_*_Stub). If the object being
147   * narrowed is connected to an ORB, the returned instance will inherit that
148   * connection, representing the same remote (or local) object, but now with
149   * the possibility to invoke remote methods. </li>
150   * <li>A CORBA object may be directly narrowed into the appropriate
151   * {@link Stub} class, if it is and passed as a second parameter. This allows
152   * to use non-standard stubs without parameterless constructors.</li>
153   * <li>Any two classes, derived from the {@link ObjectImpl} (may be Stub's)
154   * can be narrowed one into another (a delegate is transferred). </li>
155   * <li>An implementation of Remote can be narrowed into {@link Tie} that can
156   * later connected to an ORB, making the methods accessible remotely. The
157   * Remote being narrowed normally provides a local implementation, but you can
158   * also narrow remote Stub, creating "forwarding Tie".</li>
159   * <li>null is narrowed into null regardless of the second parameter.</li>
160   * <li>A {@link Tie} can be narrowed into Remote, representing the
161   * implementation for this Tie (if one is set).</li>
162   * </ul>
163   *
164   * @param object the object like CORBA Object, Stub or Remote that must be
165   * narrowed to the given interface.
166   *
167   * @param narrowToInstaceOf the class of the interface to that the object must
168   * be narrowed.
169   *
170   * @return On success, an object of type narrowTo or null, if narrowFrom =
171   * null.
172   *
173   * @throws ClassCastException if no narrowing is possible.
174   */
175  public static Object narrow(Object object, Class narrowToInstaceOf)
176    throws ClassCastException
177  {
178    return delegate.narrow(object, narrowToInstaceOf);
179  }
180
181  /**
182   * <p>
183   * Takes a server implementation object (name pattern *imp) and returns a stub
184   * object that can be used to access that server object (target), name
185   * (pattern _*_Stub).
186   *
187   * The returned stub is not connected to any ORB and must be explicitly
188   * connected using {@link #connect}.
189   * </p>
190   * <p>
191   * The method signature prevents it from returning stubs that does not
192   * implement Remote (ClassCastException will be thrown).
193   * </p>
194   *
195   * @param target a server side object implementation.
196   * @return a stub object that can be used to access that server object.
197   *
198   * @throws NoSuchObjectException if a stub class cannot be located by supposed
199   * name pattern, or an instance of stub fails to be instantiated.
200   *
201   * @throws ClassCastException if the stub class can be located, but it does
202   * not inherit from Remote.
203   *
204   * @throws BAD_PARAM if the name of the passed class does not match the
205   * implementation name pattern (does not end by 'Impl').
206   */
207  public static Remote toStub(Remote targetImpl)
208    throws NoSuchObjectException
209  {
210    return delegate.toStub(targetImpl);
211  }
212
213  /**
214   * Deregister a currently exported server object from the ORB runtimes. The
215   * object to becomes available for garbage collection. This is usually
216   * impemented via {@link Util#unexportObject}
217   *
218   * @param object the object to unexport.
219   *
220   * @throws NoSuchObjectException if the passed object is not currently
221   * exported.
222   */
223  public static void unexportObject(Remote object)
224    throws NoSuchObjectException
225  {
226    delegate.unexportObject(object);
227  }
228}