Stub


1   /***
2    * Fractal RMI: a binder for remote method calls between Fractal components.
3    * Copyright (C) 2003 France Telecom R&D
4    *
5    * This library is free software; you can redistribute it and/or
6    * modify it under the terms of the GNU Lesser General Public
7    * License as published by the Free Software Foundation; either
8    * version 2 of the License, or (at your option) any later version.
9    *
10   * This library is distributed in the hope that it will be useful,
11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13   * Lesser General Public License for more details.
14   *
15   * You should have received a copy of the GNU Lesser General Public
16   * License along with this library; if not, write to the Free Software
17   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
18   *
19   * Contact: Eric.Bruneton@rd.francetelecom.com
20   *
21   * Author: Eric Bruneton
22   *
23   * with some code fragments copied from Jonathan:
24   *   org.objectweb.jeremie.libs.stub_factories.std.RefImpl
25   *     (authors: B. Dumant, K. Milsted)
26   */
27  
28  package org.objectweb.fractal.rmi.stub;
29  
30  import org.objectweb.fractal.api.Component;
31  import org.objectweb.fractal.api.Interface;
32  import org.objectweb.fractal.api.Type;
33  
34  import org.objectweb.fractal.rmi.RemoteException;
35  
36  import org.objectweb.jonathan.apis.binding.Identifier;
37  import org.objectweb.jonathan.apis.binding.Reference;
38  import org.objectweb.jonathan.apis.kernel.JonathanException;
39  import org.objectweb.jonathan.apis.presentation.MarshalException;
40  import org.objectweb.jonathan.apis.presentation.Marshaller;
41  import org.objectweb.jonathan.apis.presentation.MarshallerFactory;
42  import org.objectweb.jonathan.apis.presentation.UnMarshaller;
43  import org.objectweb.jonathan.apis.protocols.ReplyInterface;
44  import org.objectweb.jonathan.apis.protocols.ServerException;
45  import org.objectweb.jonathan.apis.protocols.SessionIdentifier;
46  import org.objectweb.jonathan.apis.protocols.Session_High;
47  
48  /**
49   * Super class of the stub classes generated by the {@link RmiStubFactory}.
50   * A stub gives access to an interface of a Fractal component.
51   * More precisely, it gives access to the "functional" interface provided by
52   * a server interface, and also gives access to the {@link Interface} interface
53   * implemented by this server interface. The
54   * "functional" interface is implemented by a sub class of this class, while
55   * the {@link Interface} interface is implemented
56   * by this class once and for all.
57   */
58  
59  public class Stub implements Reference, Interface {
60  
61    /**
62     * The identifier of the remote object to which this stub gives access.
63     */
64  
65    protected Identifier id;
66  
67    /**
68     * The marshaller factory to be used to create new invocation messages.
69     */
70  
71    protected MarshallerFactory marshallerFactory;
72  
73    /**
74     * The identifier of the session that gives access to the remote object.
75     */
76  
77    protected SessionIdentifier sessionId;
78  
79    /**
80     * The session that gives access to the remote object. This session is used to
81     * send the invocation messages down the protocol stack.
82     */
83  
84    protected Session_High session;
85  
86    /**
87     * Constructs a new {@link Stub}.
88     */
89  
90    public Stub () {
91    }
92  
93    // --------------------------------------------------------------------------
94    // Implementation of the Reference interface
95    // --------------------------------------------------------------------------
96  
97    /**
98     * Returns the set of identifiers associated with this reference.
99     *
100    * @return the set of identifiers associated with this reference.
101    * @see #setIdentifiers
102    */
103 
104   public Identifier[] getIdentifiers () {
105     return new Identifier[] { id };
106   }
107 
108   /**
109    * Sets the set of identifiers associated with this reference.
110    *
111    * @param ids the set of identifiers to be associated with this reference.
112    * @see #getIdentifiers
113    */
114 
115   public void setIdentifiers (Identifier[] ids) {
116     this.id = ids[0];
117   }
118 
119   // --------------------------------------------------------------------------
120   // Implementation of the Interface interface
121   // --------------------------------------------------------------------------
122 
123   public Component getFcItfOwner () {
124     try {
125       Marshaller marshaller = request();
126       ReplyInterface reply = prepareInvocation(marshaller);
127       marshaller.writeInt(-1);
128       invoke(marshaller);
129       UnMarshaller unmarshaller = reply.listen();
130       Component result = (Component)unmarshaller.readValue();
131       unmarshaller.close();
132       return result;
133     } catch (Exception   e) {
134       e = handleException(e);
135       if (e instanceof RuntimeException  ) {
136         throw (RuntimeException  )e;
137       } else {
138         throw new RemoteException("server side exception", e);
139       }
140     }
141   }
142 
143   public String   getFcItfName () {
144     try {
145       Marshaller marshaller = request();
146       ReplyInterface reply = prepareInvocation(marshaller);
147       marshaller.writeInt(-2);
148       invoke(marshaller);
149       UnMarshaller unmarshaller = reply.listen();
150       String   result = (String  )unmarshaller.readValue();
151       unmarshaller.close();
152       return result;
153     } catch (Exception   e) {
154       e = handleException(e);
155       if (e instanceof RuntimeException  ) {
156         throw (RuntimeException  )e;
157       } else {
158         throw new RemoteException("server side exception", e);
159       }
160     }
161   }
162 
163   public Type getFcItfType () {
164     try {
165       Marshaller marshaller = request();
166       ReplyInterface reply = prepareInvocation(marshaller);
167       marshaller.writeInt(-3);
168       invoke(marshaller);
169       UnMarshaller unmarshaller = reply.listen();
170       Type result = (Type)unmarshaller.readValue();
171       unmarshaller.close();
172       return result;
173     } catch (Exception   e) {
174       e = handleException(e);
175       if (e instanceof RuntimeException  ) {
176         throw (RuntimeException  )e;
177       } else {
178         throw new RemoteException("server side exception", e);
179       }
180     }
181   }
182 
183   public boolean isFcInternalItf () {
184     try {
185       Marshaller marshaller = request();
186       ReplyInterface reply = prepareInvocation(marshaller);
187       marshaller.writeInt(-4);
188       invoke(marshaller);
189       UnMarshaller unmarshaller = reply.listen();
190       boolean result = unmarshaller.readBoolean();
191       unmarshaller.close();
192       return result;
193     } catch (Exception   e) {
194       e = handleException(e);
195       if (e instanceof RuntimeException  ) {
196         throw (RuntimeException  )e;
197       } else {
198         throw new RemoteException("server side exception", e);
199       }
200     }
201   }
202 
203   // --------------------------------------------------------------------------
204   // Utility methods
205   // --------------------------------------------------------------------------
206 
207   /**
208    * Obtains a marshaller for marshalling invocation data.
209    *
210    * @return a marshaller for marshalling invocation data.
211    * @throws MarshalException if something goes wrong.
212    */
213 
214   protected Marshaller request () throws MarshalException {
215     if (marshallerFactory == null) {
216       throw new MarshalException("null marshaller factory");
217     }
218     return marshallerFactory.newMarshaller();
219   }
220 
221   /**
222    * Prepares the marshaller prior to marshalling invocation data. This
223    * preparation is protocol-specific and typically consists of adding headers
224    * to the marshaller. In line with Java method invocation semantics, a reply
225    * is expected after the remote invocation is executed; a reply interface
226    * is thus returned in order to listen for the reply.
227    *
228    * @param marshaller a marshaller to be used for the invocation data.
229    * @return a reply interface for listening for the reply.
230    * @throws MarshalException if something goes wrong.
231    */
232 
233   protected ReplyInterface prepareInvocation (final Marshaller marshaller)
234     throws MarshalException
235   {
236     try {
237       synchronized(this) {
238         if (session == null) {
239           session = sessionId.bind(null);
240         }
241       }
242       return session.prepareInvocation(marshaller);
243     } catch (Exception   e) {
244       throw new MarshalException("exception preparing marshaller: " + e);
245     }
246   }
247 
248   /**
249    * Sends the marshaller with the invocation data down the protocol stack.
250    *
251    * @param marshaller a marshaller with the invocation data.
252    * @throws MarshalException if something goes wrong.
253    */
254 
255   protected void invoke (final Marshaller marshaller) throws MarshalException {
256     try {
257       synchronized(this) {
258         if (session == null) {
259           throw new MarshalException("null session");
260         }
261       }
262       session.send(marshaller);
263     } catch (Exception   e) {
264       throw new MarshalException("exception at invocation: "  + e);
265     }
266   }
267 
268   /**
269    * Handles an exception that happen in this stub.
270    *
271    * @param e an exception.
272    * @return the exception encapsulated in the given exception (if it is a
273    *      {@link ServerException}, i.e., an exception that was
274    *      thrown by the remote object and sent back in a reply message), or a
275    *      new {@link RemoteException} encaspulating the given
276    *      exception in the other cases (case of an exception that was thrown
277    *      locally by the stub itself).
278    */
279 
280   protected Exception   handleException (final Exception   e) {
281     if (e instanceof ServerException) {
282       try {
283         UnMarshaller unmarshaller = ((ServerException)e).unmarshaller;
284         Exception   f = (Exception  )unmarshaller.readValue();
285         unmarshaller.close();
286         return f;
287       } catch (JonathanException je) {
288         return new RemoteException(
289           "error during exception unmarshalling by stub", je);
290       }
291     } else {
292       return new RemoteException(
293         "error during marshalling/unmarshalling by stub", e);
294     }
295   }
296 
297   protected Object   replaceClassName (Object   o) throws ClassNotFoundException   {
298     if (o instanceof String  ) {
299       return Class.forName((String  )o);
300     } else if (o instanceof Object  []) {
301       Object  [] desc = (Object  [])o;
302       if (desc.length == 2 && desc[1] instanceof String  ) {
303         return new Object  [] { desc[0], Class.forName((String  )desc[1]) };
304       }
305     }
306     return o;
307   }
308   
309   protected Object   replaceClassValue (Object   o) {
310     if (o instanceof Class  ) {
311       return ((Class  )o).getName();
312     } else if (o instanceof Object  []) {
313       Object  [] desc = (Object  [])o;
314       if (desc.length == 2 && desc[1] instanceof Class  ) {
315         return new Object  [] { desc[0], ((Class  )desc[1]).getName() };
316       }
317     }
318     return o;
319   }
320 
321   // --------------------------------------------------------------------------
322   // Overriden methods
323   // --------------------------------------------------------------------------
324 
325   /**
326    * Tests if the given object is equal to this stub.
327    *
328    * @param o the object to be compared to this stub.
329    * @return <tt>true</tt> if the given object is a stub whose {@link #id id} is
330    *      equal to the {@link #id id} of this stub, <tt>false</tt> otherwise.
331    */
332 
333   public boolean equals (final Object   o) {
334     if (o instanceof Stub) {
335       return id.equals(((Stub)o).id);
336     }
337     return false;
338   }
339 
340   /**
341    * Returns the hashcode of this stub.
342    *
343    * @return the hashcode of the {@link #id id} of this stub.
344    */
345 
346   public int hashCode () {
347     return id.hashCode();
348   }
349 
350   /**
351    * Finalizes this object. This method closes the {@link #session session}
352    * associated to this stub if it is not <tt>null</tt>.
353    */
354 
355   protected void finalize () {
356     if (session != null) {
357       session.close();
358       session = null;
359     }
360   }
361 }
362
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