ActiveMQTopicSubscriber


1   /**
2    *
3    * Licensed to the Apache Software Foundation (ASF) under one or more
4    * contributor license agreements.  See the NOTICE file distributed with
5    * this work for additional information regarding copyright ownership.
6    * The ASF licenses this file to You under the Apache License, Version 2.0
7    * (the "License"); you may not use this file except in compliance with
8    * the License.  You may obtain a copy of the License at
9    *
10   * http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing, software
13   * distributed under the License is distributed on an "AS IS" BASIS,
14   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15   * See the License for the specific language governing permissions and
16   * limitations under the License.
17   */
18  
19  package org.apache.activemq;
20  
21  import org.apache.activemq.command.ActiveMQDestination;
22  import org.apache.activemq.command.ConsumerId;
23  
24  import javax.jms.JMSException  ;
25  import javax.jms.Topic  ;
26  import javax.jms.TopicSubscriber  ;
27  
28  /**
29   * A client uses a <CODE>TopicSubscriber</CODE> object to receive messages
30   * that have been published to a topic. A <CODE>TopicSubscriber</CODE> object
31   * is the publish/subscribe form of a message consumer. A <CODE>
32   * MessageConsumer</CODE> can be created by using <CODE>
33   * Session.createConsumer</CODE>.
34   * <p/>
35   * <P>
36   * A <CODE>TopicSession</CODE> allows the creation of multiple <CODE>
37   * TopicSubscriber</CODE> objects per topic. It will deliver each message for
38   * a topic to each subscriber eligible to receive it. Each copy of the message
39   * is treated as a completely separate message. Work done on one copy has no
40   * effect on the others; acknowledging one does not acknowledge the others; one
41   * message may be delivered immediately, while another waits for its subscriber
42   * to process messages ahead of it.
43   * <p/>
44   * <P>
45   * Regular <CODE>TopicSubscriber</CODE> objects are not durable. They receive
46   * only messages that are published while they are active.
47   * <p/>
48   * <P>
49   * Messages filtered out by a subscriber's message selector will never be
50   * delivered to the subscriber. From the subscriber's perspective, they do not
51   * exist.
52   * <p/>
53   * <P>
54   * In some cases, a connection may both publish and subscribe to a topic. The
55   * subscriber <CODE>NoLocal</CODE> attribute allows a subscriber to inhibit
56   * the delivery of messages published by its own connection.
57   * <p/>
58   * <P>
59   * If a client needs to receive all the messages published on a topic,
60   * including the ones published while the subscriber is inactive, it uses a
61   * durable <CODE>TopicSubscriber</CODE>. The JMS provider retains a record
62   * of this durable subscription and insures that all messages from the topic's
63   * publishers are retained until they are acknowledged by this durable
64   * subscriber or they have expired.
65   * <p/>
66   * <P>
67   * Sessions with durable subscribers must always provide the same client
68   * identifier. In addition, each client must specify a name that uniquely
69   * identifies (within client identifier) each durable subscription it creates.
70   * Only one session at a time can have a <CODE>TopicSubscriber</CODE> for a
71   * particular durable subscription.
72   * <p/>
73   * <P>
74   * A client can change an existing durable subscription by creating a durable
75   * <CODE>TopicSubscriber</CODE> with the same name and a new topic and/or
76   * message selector. Changing a durable subscription is equivalent to
77   * unsubscribing (deleting) the old one and creating a new one.
78   * <p/>
79   * <P>
80   * The <CODE>unsubscribe</CODE> method is used to delete a durable
81   * subscription. The <CODE>unsubscribe</CODE> method can be used at the
82   * <CODE>Session</CODE> or <CODE>TopicSession</CODE> level. This method
83   * deletes the state being maintained on behalf of the subscriber by its
84   * provider.
85   * <p/>
86   * <P>
87   * Creating a <CODE>MessageConsumer</CODE> provides the same features as
88   * creating a <CODE>TopicSubscriber</CODE>. To create a durable subscriber,
89   * use of <CODE>Session.CreateDurableSubscriber</CODE> is recommended. The
90   * <CODE>TopicSubscriber</CODE> is provided to support existing code.
91   *
92   * @see javax.jms.Session#createConsumer
93   * @see javax.jms.Session#createDurableSubscriber
94   * @see javax.jms.TopicSession
95   * @see javax.jms.TopicSession#createSubscriber
96   * @see javax.jms.TopicSubscriber
97   * @see javax.jms.MessageConsumer
98   */
99  
100 public class ActiveMQTopicSubscriber extends ActiveMQMessageConsumer implements
101         TopicSubscriber   {
102 
103     /**
104      * @param theSession
105      * @param value 
106      * @param dest
107      * @param name
108      * @param selector
109      * @param cnum
110      * @param noLocalValue
111      * @param browserValue
112      * @param asyncDispatch 
113      * @throws JMSException
114      */
115     protected ActiveMQTopicSubscriber(ActiveMQSession theSession,
116                                       ConsumerId consumerId, ActiveMQDestination dest, String   name, String   selector, int prefetch, int maximumPendingMessageCount,
117                                       boolean noLocalValue, boolean browserValue, boolean asyncDispatch) throws JMSException   {
118         super(theSession, consumerId, dest, name, selector, prefetch, maximumPendingMessageCount, noLocalValue, browserValue, asyncDispatch);
119     }
120 
121     /**
122      * Gets the <CODE>Topic</CODE> associated with this subscriber.
123      *
124      * @return this subscriber's <CODE>Topic</CODE>
125      * @throws JMSException if the JMS provider fails to get the topic for this topic
126      *                      subscriber due to some internal error.
127      */
128 
129     public Topic   getTopic() throws JMSException   {
130         checkClosed();
131         return (Topic  ) super.getDestination();
132     }
133 
134     /**
135      * Gets the <CODE>NoLocal</CODE> attribute for this subscriber. The
136      * default value for this attribute is false.
137      *
138      * @return true if locally published messages are being inhibited
139      * @throws JMSException if the JMS provider fails to get the <CODE>NoLocal
140      *                      </CODE> attribute for this topic subscriber due to some
141      *                      internal error.
142      */
143 
144     public boolean getNoLocal() throws JMSException   {
145         checkClosed();
146         return super.isNoLocal();
147     }
148 }
149
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