ServerTable


1   package org.jacorb.imr;
2   
3   /*
4    *        JacORB - a free Java ORB
5    *
6    *   Copyright (C) 1997-2004 Gerald Brose.
7    *
8    *   This library is free software; you can redistribute it and/or
9    *   modify it under the terms of the GNU Library General Public
10   *   License as published by the Free Software Foundation; either
11   *   version 2 of the License, or (at your option) any later version.
12   *
13   *   This library is distributed in the hope that it will be useful,
14   *   but WITHOUT ANY WARRANTY; without even the implied warranty of
15   *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
16   *   Library General Public License for more details.
17   *
18   *   You should have received a copy of the GNU Library General Public
19   *   License along with this library; if not, write to the Free
20   *   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21   */
22  
23  import java.util.*;
24  import java.io.*;
25  import org.jacorb.imr.RegistrationPackage.*;
26  import org.jacorb.imr.AdminPackage.*;
27  
28  /**
29   * This class represents the server table of the implementation repository.
30   * It contains all servers, POAs and hosts, and is serialized on shutdown,
31   * deserialized on startup.
32   * <br> It provides methods for adding, deleting and listing servers, 
33   * POAs and hosts.
34   *
35   * @author Nicolas Noffke
36   * 
37   * $Id: ServerTable.java,v 1.10 2004/05/06 12:39:59 nicolas Exp $
38   */
39  
40  public class ServerTable 
41      implements Serializable 
42  {
43      private Hashtable servers;
44      private transient ResourceLock servers_lock;
45      private Hashtable poas;
46      private transient ResourceLock poas_lock;
47      private Hashtable hosts;
48      private transient ResourceLock hosts_lock;
49  
50      public transient ResourceLock table_lock;
51  
52      public ServerTable() 
53      {
54          servers = new Hashtable();
55          poas = new Hashtable();
56          hosts = new Hashtable();
57  
58          initTransient();
59      }
60  
61      /**
62       * This method initializes all transient attributes.
63       */
64  
65      private void initTransient()
66      {
67          // The table lock is a special case. It is used to gain
68          // exclusive access to the server table on serialization. That
69          // means the exclusive lock is set on serialization and, if it
70          // was not transient, would be serialized as well.  On startup
71          // of the repository, if the table is deserialized, the lock
72          // is still set, und must be realeased. That means that we
73          // have to distinguish between a new table and a deserialized
74          // one. So its cheaper to instanciate the lock on
75          // deserialization time again.
76          table_lock = new ResourceLock();
77  
78          // The locks are needed, because the hashtables have to be
79          // copied to arrays sometimes (usually on command of the
80          // user), and that is done via Enumerations.  Unfortunately
81          // Enumerations get messed up when altering the underlying
82          // structure while reading from them.
83          servers_lock = new ResourceLock();
84          poas_lock = new ResourceLock();
85          hosts_lock = new ResourceLock();
86      }
87  
88      /**
89       * This method tests, if a server is known.
90       *
91       * @param name the servers name.
92       * @return true, if a server with the specified name has already
93       * been registered.
94       */
95  
96      public boolean hasServer( String   name )
97      {
98          return servers.containsKey(name);
99      }
100 
101 
102     /**
103      * This method gets a server for a specified name.
104      *
105      * @param name the servers name.
106      * @return ImRServerInfo the ImRServerInfo object with name <code>name</code>.
107      * @exception UnknownServerName thrown if the table does not contain 
108      * an entry for <code>name</code>.
109      */
110 
111     public ImRServerInfo getServer(String   name)
112         throws UnknownServerName
113     {
114         ImRServerInfo _tmp = (ImRServerInfo) servers.get(name);
115         if (_tmp == null)
116             throw new UnknownServerName(name);
117 
118         return _tmp;
119     }
120 
121     /**
122      * Adds a server to the server table.
123      *
124      * @param name the servers name.
125      * @param server the servers corresponding ImRServerInfo object.
126      * @exception DuplicateServerName thrown if <code>name</code> is already
127      * in the table.
128      */
129 
130     public void putServer(String   name, ImRServerInfo server)
131         throws DuplicateServerName
132     {
133         if (servers.containsKey(name))
134             throw new DuplicateServerName(name);
135 
136         table_lock.gainSharedLock();
137         servers_lock.gainSharedLock();
138 
139         servers.put(name, server);
140 
141         servers_lock.releaseSharedLock();
142         table_lock.releaseSharedLock();
143     }
144 
145     /**
146      * Remove a server from the server table.
147      *
148      * @param name the servers name.
149      * @exception UnknownServerName thrown if no server with <code>name</code>
150      * is found in the table.
151      */
152 
153     public void removeServer(String   name)
154         throws UnknownServerName
155     {
156         table_lock.gainSharedLock();
157         servers_lock.gainSharedLock();
158 
159         Object   _obj = servers.remove(name);
160 
161         servers_lock.releaseSharedLock();
162         table_lock.releaseSharedLock();
163 
164         if (_obj == null)
165             throw new UnknownServerName(name);
166     }
167 
168     /**
169      * Get the ImRPOAInfo object of a POA.
170      *
171      * @param name the POAs name.
172      * @return the ImRPOAInfo object for <code>name</code>, 
173      * null if <code>name</code> not in the table.
174      */
175 
176     public ImRPOAInfo getPOA (String   name)
177     {
178         return (ImRPOAInfo) poas.get(name);
179     }
180 
181     /**
182      * Add a POA to the server table.
183      *
184      * @param name the POAs name.
185      * @param poa the POAs ImRPOAInfo object.
186      */
187 
188     public void putPOA(String   name, ImRPOAInfo poa)
189     {
190         table_lock.gainSharedLock();
191         poas_lock.gainSharedLock();
192 
193         poas.put(name, poa);
194 
195         poas_lock.releaseSharedLock();
196         table_lock.releaseSharedLock();
197     }
198 
199     /**
200      * Remove a POA from the server table.
201      *
202      * @param name the POAs name.
203      */
204 
205     public void removePOA(String   name)
206     {
207         table_lock.gainSharedLock();
208         poas_lock.gainSharedLock();
209 
210         poas.remove(name);
211 
212         poas_lock.releaseSharedLock();
213         table_lock.releaseSharedLock();
214     }
215 
216     /**
217      * List all servers in the table.
218      *
219      * @return a ServerInfo array containing all servers.
220      * Used by the CORBA interface of the repository.
221      */
222 
223     public ServerInfo[] getServers()
224     {
225         table_lock.gainSharedLock();
226         servers_lock.gainExclusiveLock();
227 
228         //build array
229         ServerInfo[] _servers = new ServerInfo[servers.size()];
230         Enumeration _server_enum = servers.elements();
231 
232         //copy elements from vector to array
233         int _i = 0;
234         while (_server_enum.hasMoreElements())
235             _servers[_i++] = ((ImRServerInfo) _server_enum.nextElement()).toServerInfo();
236 
237         servers_lock.releaseExclusiveLock();
238         table_lock.releaseSharedLock();
239 
240         return _servers;
241     }
242 
243     /**
244      * List all hosts in the table.
245      *
246      * @return a HostInfo array containing all hosts.
247      * Used by the CORBA interface of the repository.
248      */
249 
250     public HostInfo[] getHosts()
251     {
252         table_lock.gainSharedLock();
253         hosts_lock.gainExclusiveLock();
254 
255         //build array
256         HostInfo[] _hosts = new HostInfo[hosts.size()];
257         Enumeration _host_enum = hosts.elements();
258     
259         //copy elements from vector to array
260         int _i = 0;
261         while (_host_enum.hasMoreElements())
262             _hosts[_i++] = ((ImRHostInfo) _host_enum.nextElement()).toHostInfo();
263     
264         hosts_lock.releaseExclusiveLock();
265         table_lock.releaseSharedLock();
266 
267         return _hosts;
268     }
269 
270     /**
271      * List all POAs in the table.
272      *
273      * @return a POAInfo array containing all POAs.
274      * Used by the CORBA interface of the repository.
275      */
276 
277     public POAInfo[] getPOAs()
278     {
279         table_lock.gainSharedLock();
280         poas_lock.gainExclusiveLock();
281 
282         //build array
283         POAInfo[] _poas = new POAInfo[poas.size()];
284         Enumeration _poa_enum = poas.elements();
285 
286         //copy elements from vector to array
287         int _i = 0;
288         while (_poa_enum.hasMoreElements())
289             _poas[_i++] = ((ImRPOAInfo) _poa_enum.nextElement()).toPOAInfo();
290     
291         poas_lock.releaseExclusiveLock();
292         table_lock.releaseSharedLock();
293 
294         return _poas;
295     }
296 
297     /**
298      * Add a host to the table. If an entry for <code>name</code> is already
299      * in the table it is overwritten.
300      *
301      * @param name the hosts name.
302      * @param host the hosts ImRHostInfo object.
303      */
304 
305     public void putHost(String   name, ImRHostInfo host)
306     {
307         table_lock.gainSharedLock();
308         hosts_lock.gainSharedLock();
309 
310         hosts.put(name, host);
311 
312         hosts_lock.releaseSharedLock();
313         table_lock.releaseSharedLock();
314     }
315 
316     /**
317      * Remove a host from the table.
318      *
319      * @param name the hosts name.
320      */
321 
322     public Object   removeHost(String   name)
323     {
324         return hosts.remove(name);
325     }
326 
327     /**
328      * Get the ImRHostInfo object of a host.
329      *
330      * @param name the hosts name.
331      * @return the ImRHostInfo object for <code>name</code>, null 
332      * if <code>name</code> not in the table.
333      */
334 
335     public ImRHostInfo getHost(String   name)
336     {
337         return (ImRHostInfo) hosts.get(name);
338     }
339 
340     /**
341      * Implemented from the Serializable interface. For 
342      * automatic initializing after deserialization.
343      */
344 
345     private void readObject(java.io.ObjectInputStream   in)
346         throws java.io.IOException  , java.io.NotActiveException  , 
347         ClassNotFoundException  
348     {
349         in.defaultReadObject();
350         initTransient();
351     }
352 } // ServerTable
353 
354 
355
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