libjava/classpath/javax/rmi/PortableRemoteObject.java

   1 /* PortableRemoteObject.java --
   2    Copyright (C) 2004, 2004, 2005 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
  39 package javax.rmi;
  40
  41 import gnu.javax.rmi.CORBA.DelegateFactory;
  42
  43 import org.omg.CORBA.BAD_PARAM;
  44 import org.omg.CORBA.ORB;
  45 import org.omg.CORBA.portable.ObjectImpl;
  46 import org.omg.PortableServer.POA;
  47 import org.omg.PortableServer.Servant;
  48
  49 import java.rmi.NoSuchObjectException;
  50 import java.rmi.Remote;
  51 import java.rmi.RemoteException;
  52
  53 import javax.rmi.CORBA.PortableRemoteObjectDelegate;
  54 import javax.rmi.CORBA.Stub;
  55 import javax.rmi.CORBA.Tie;
  56 import javax.rmi.CORBA.Util;
  57
  58 /**
  59  * <p>
  60  * An utility class for RMI/IDL server side object implementations. Server side
  61  * implementation objects may inherit from this class, but this is not
  62  * mandatory, as the needed methds are static. Server side implementations may
  63  * choose to inherit from {@link ObjectImpl} or {@link Servant} instead.
  64  * </p>
  65  * <p>
  66  * The functionality of methods in this class is forwarded to the enclosed
  67  * PortableRemoteObjectDelegate. This delegate can be altered by setting the
  68  * system property "javax.rmi.CORBA.PortableRemoteObjectClass" to the name of
  69  * the alternative class that must implement
  70  * {@link PortableRemoteObjectDelegate}.
  71  * </p>
  72  *
  73  * @author Audrius Meskauskas (AudriusA@Bioinformatics.org)
  74  */
  75 public class PortableRemoteObject
  76 {
  77   /**
  78    * A delegate where the functionality is forwarded.
  79    */
  80   static PortableRemoteObjectDelegate delegate = (PortableRemoteObjectDelegate) DelegateFactory.getInstance(DelegateFactory.PORTABLE_REMOTE_OBJECT);
  81
  82   /**
  83    * The protected constructor calls {@link exportObject} (this).
  84    *
  85    * @throws RemoteException if the exportObject(this) throws one.
  86    */
  87   protected PortableRemoteObject()
  88     throws RemoteException
  89   {
  90     exportObject((Remote) this);
  91   }
  92
  93   /**
  94    * <p>
  95    * Makes the remote object <code>a_target</code> ready for remote
  96    * communication using the same communications runtime as for the passed
  97    * <code>a_source</code> parameter. The a_target is connected to the same
  98    * ORB (and, if applicable, to the same {@link POA}) as the a_source.
  99    *
 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 }