ClientServerConsistencyWrapper


1   /*
2     Copyright (C) 2001 Renaud Pawlak renaud@aopsys.com
3   
4     This program is free software; you can redistribute it and/or modify
5     it under the terms of the GNU Lesser General Public License as
6     published by the Free Software Foundation; either version 2 of the
7     License, or (at your option) any later version.
8   
9     This program is distributed in the hope that it will be useful,
10    but WITHOUT ANY WARRANTY; without even the implied warranty of
11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12    GNU Lesser General Public License for more details.
13  
14    You should have received a copy of the GNU Lesser General Public License
15    along with this program; if not, write to the Free Software
16    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
17  
18  package org.objectweb.jac.aspects.distribution.consistency;
19  
20  import java.util.*;
21  import org.apache.log4j.Logger;
22  import org.objectweb.jac.core.*;
23  import org.objectweb.jac.core.dist.*;
24  import org.objectweb.jac.core.rtti.ClassRepository;
25  import org.objectweb.jac.util.*;
26  
27  /**
28   * This wrapper implements a client-server consistency protocol.
29   *
30   * <p>It is a special consistency protocol since the wrappee acts as a
31   * pure client (a stub) for its known replicas.<p>
32   * 
33   * @author <a HREF="http://cedric.cnam.fr/~pawlak/index-english.html">Renaud Pawlak</a> */
34  
35  public class ClientServerConsistencyWrapper extends ConsistencyWrapper {
36      static Logger logger = Logger.getLogger("consistency");
37  
38      String   hosts = null;
39  
40      /**
41      * A friendly constructor for a client-server consistency wrapper.
42      *
43      * @param hosts a regular expression that defines the host where
44      * the server is located 
45      */
46      public ClientServerConsistencyWrapper(AspectComponent ac, String   hosts) {
47          super(ac);
48          knownReplicas = null;
49          this.hosts = hosts;
50      } 
51  
52      /** An empty constructor for the Consistency class. */
53      public ClientServerConsistencyWrapper(AspectComponent ac) {
54          super(ac);
55      }
56  
57      /**
58      * Forwards the call to the server(s).<p>
59      *
60      * Do not call the replica except if we do not know any server (in
61      * this case, we are a server).<p>
62      *
63      * @return the value returned by the server */
64  
65      public Object   whenCall(Interaction interaction) {
66  
67          if( knownReplicas == null ) {
68              knownReplicas = Topology.getPartialTopology(hosts).getReplicas(interaction.wrappee);
69          } 
70  
71          if(knownReplicas != null && knownReplicas.size() > 0 &&
72             (! ((RemoteRef)knownReplicas.get(0)).getRemCont().isLocal()) ) {
73              logger.debug("(client-server) call event on " + 
74                        NameRepository.get().getName(interaction.wrappee) + 
75                        ":" + interaction.method + ":" + 
76                        ((RemoteRef)knownReplicas.get(0)).getRemCont().getName());
77              Object   ret = ((RemoteRef)knownReplicas.get(0)).invokeRoleMethod(
78                  "acceptRemoteCall",
79                  new Object  [] { null, new Object  [] { interaction.method, interaction.args } }
80              );
81              return ret;
82          } else {
83              /* we do not know any replica, so we are the server... */
84              return proceed(interaction);
85          }
86      }
87  
88      /**
89      * Calls the method on the server.
90      *
91      * @param remoteReplica the client remote reference
92      * @param data the name and the parameters of the server method
93      */
94  
95      public Object   acceptRemoteCall(Wrappee wrappee, RemoteRef remoteReplica,
96                                     Object  [] data) {
97          logger.debug("(client-server) remote call event on " + 
98                       NameRepository.get().getName(wrappee) +
99                       ":" + (String  )data[0] + ":" + 
100                      Arrays.asList((Object  [])data[1]));
101         return ClassRepository.get().getClass(wrappee).getMethod((String  )data[0]).invoke(
102             wrappee , (Object  [])data[1] );
103     }
104 }
105
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