QueueBrowser


1   /*
2    * JORAM: Java(TM) Open Reliable Asynchronous Messaging
3    * Copyright (C) 2001 - 2006 ScalAgent Distributed Technologies
4    * Copyright (C) 1996 - 2000 Dyade
5    *
6    * This library is free software; you can redistribute it and/or
7    * modify it under the terms of the GNU Lesser General Public
8    * License as published by the Free Software Foundation; either
9    * version 2.1 of the License, or any later version.
10   * 
11   * This library is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
14   * Lesser General Public License for more details.
15   * 
16   * You should have received a copy of the GNU Lesser General Public
17   * License along with this library; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
19   * USA.
20   *
21   * Initial developer(s): Frederic Maistre (INRIA)
22   * Contributor(s): ScalAgent Distributed Technologies
23   */
24  package org.objectweb.joram.client.jms;
25  
26  import java.util.*;
27  
28  import javax.jms.InvalidSelectorException  ;
29  import javax.jms.InvalidDestinationException  ;
30  import javax.jms.IllegalStateException  ;
31  import javax.jms.JMSException  ;
32  
33  import org.objectweb.joram.shared.client.*;
34  import org.objectweb.joram.shared.selectors.ClientSelector;
35  
36  import org.objectweb.util.monolog.api.BasicLevel;
37  import org.objectweb.joram.shared.JoramTracing;
38  
39  /**
40   * Implements the <code>javax.jms.QueueBrowser</code> interface.
41   */
42  public class QueueBrowser implements javax.jms.QueueBrowser   {
43    /** The session the browser belongs to. */
44    private Session sess;
45  
46    /** The queue the browser browses. */
47    private Queue queue;
48  
49    /** The selector for filtering messages. */
50    private String   selector;
51  
52    /** <code>true</code> if the browser is closed. */
53    private boolean closed = false;
54  
55    /**
56     * Constructs a browser.
57     *
58     * @param sess  The session the browser belongs to.
59     * @param queue  The queue the browser browses.
60     * @param selector  The selector for filtering messages.
61     *
62     * @exception InvalidSelectorException  If the selector syntax is invalid.
63     * @exception IllegalStateException  If the connection is broken.
64     * @exception JMSException  If the creation fails for any other reason.
65     */
66    QueueBrowser(Session sess, Queue queue, String   selector) throws JMSException   {
67      if (queue == null)
68        throw new InvalidDestinationException  ("Invalid queue: " + queue);
69  
70      try {
71        ClientSelector.checks(selector);
72      } catch (org.objectweb.joram.shared.excepts.SelectorException sE) {
73        throw new InvalidSelectorException  ("Invalid selector syntax: " + sE);
74      }
75  
76      this.sess = sess;
77      this.queue = queue;
78      this.selector = selector;
79  
80      if (JoramTracing.dbgClient.isLoggable(BasicLevel.DEBUG))
81        JoramTracing.dbgClient.log(BasicLevel.DEBUG, this + ": created.");
82    }
83  
84    /** Returns a string view of this browser. */
85    public String   toString() {
86      return "QueueBrowser:" + sess.getId();
87    }
88  
89    /** 
90     * API method.
91     *
92     * @exception IllegalStateException  If the browser is closed.
93     */
94    public synchronized javax.jms.Queue   getQueue() throws JMSException   {
95      if (closed)
96        throw new IllegalStateException  ("Forbidden call on a closed browser.");
97  
98      return queue;
99    }
100 
101   /** 
102    * API method.
103    *
104    * @exception IllegalStateException  If the browser is closed.
105    */
106   public synchronized String   getMessageSelector() throws JMSException   {
107     if (closed)
108       throw new IllegalStateException  ("Forbidden call on a closed browser.");
109 
110     return selector;
111   }
112 
113   /**
114    * API method.
115    *
116    * @exception IllegalStateException  If the browser is closed, or if the
117    *              connection is broken.
118    * @exception JMSSecurityException  If the client is not a READER on the
119    *              queue.
120    * @exception JMSException  If the request fails for any other reason.
121    */
122   public synchronized Enumeration getEnumeration() throws JMSException   {
123     if (JoramTracing.dbgClient.isLoggable(BasicLevel.DEBUG))
124       JoramTracing.dbgClient.log(BasicLevel.DEBUG,
125                                  this + ": requests an enumeration.");
126 
127     if (closed)
128       throw new IllegalStateException  ("Forbidden call on a closed browser.");
129 
130     // Sending a "browse" request:
131     QBrowseRequest browReq = new QBrowseRequest(queue.getName(), selector);
132     // Expecting an answer:
133     QBrowseReply reply = (QBrowseReply) sess.syncRequest(browReq);
134 
135     if (JoramTracing.dbgClient.isLoggable(BasicLevel.DEBUG))
136       JoramTracing.dbgClient.log(BasicLevel.DEBUG,
137                                  this + ": received an enumeration.");
138 
139     // Processing the received messages
140     Vector messages = reply.getMessages();
141     // Return an enumeration:
142     return new QueueEnumeration(reply.getMessages());
143   }
144 
145   /**
146    * API method.
147    *
148    * @exception JMSException  Actually never thrown.
149    */
150   public synchronized void close() throws JMSException   {
151     // Ignoring the call if the browser is already closed:
152     if (closed)
153       return;
154 
155     sess.closeBrowser(this);
156     closed = true;
157 
158     if (JoramTracing.dbgClient.isLoggable(BasicLevel.DEBUG))
159       JoramTracing.dbgClient.log(BasicLevel.DEBUG, this + " closed.");
160   }
161 
162   /**
163    * The <code>QueueEnumeration</code> class is used to enumerate the browses
164    * sent by queues.
165    */
166   private class QueueEnumeration implements java.util.Enumeration   {
167     /** The vector of messages. */
168     private Vector messages;
169 
170     /**
171      * Constructs a <code>QueueEnumeration</code> instance.
172      *
173      * @param messages  The vector of messages to enumerate.
174      */
175     private QueueEnumeration(Vector messages) {
176       this.messages = messages;
177     }
178 
179     /** API method. */
180     public boolean hasMoreElements() {
181       if (messages == null)
182         return false;
183       return (! messages.isEmpty());
184     }
185 
186     /** API method. */
187     public Object   nextElement() {
188       if (messages == null || messages.isEmpty())
189         throw new NoSuchElementException();
190 
191       Message jmsMsg = null;
192       org.objectweb.joram.shared.messages.Message msg = null;
193       try {
194         msg = (org.objectweb.joram.shared.messages.Message) messages.remove(0);
195         jmsMsg = Message.wrapMomMessage(null, msg);
196       } catch (JMSException   exc) {
197         JoramTracing.dbgClient.log(BasicLevel.ERROR,
198                                    this + ", bad message: " + msg, exc);
199       }
200       return jmsMsg;
201     }
202   }
203 }
204
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