一个简单的jms聊天室示例程序，pub/sub模型

不使用maven及spring，创建简单的JMS发布/订阅示例

1.准备工作：下载activeMQ的jar包，本文使用最新稳定版5.14.2；创建java工程，导入jar包

2.在工程下创建jndi.properties配置文件

java.naming.factory.initial = org.apache.activemq.jndi.ActiveMQInitialContextFactory
java.naming.provider.url = tcp://localhost:61616
java.naming.security.principal=system
java.naming.security.credentials=manager

connectionFactoryNames=TopicCF
topic.topic1=jms.topic1

3.在active的config目录下，修改activemq.xml,在<broker>下添加，启动activemq.bat

<destinations>
　　<topic name="topic1" physicalName="jms.topic1" />
</destinations>

4.创建java类

public class Chat implements javax.jms.MessageListener{
    private TopicSession pubSession;
    private TopicPublisher publisher;
    private TopicConnection connection;
    private String username;

    /* Constructor used to Initialize Chat */
    public Chat(String topicFactory, String topicName, String username) 
        throws Exception {
        
        // Obtain a JNDI connection using the jndi.properties file
        InitialContext ctx = new InitialContext();

        // Look up a JMS connection factory
        TopicConnectionFactory conFactory = 
            (TopicConnectionFactory)ctx.lookup(topicFactory);

        // Create a JMS connection
        TopicConnection connection = conFactory.createTopicConnection();

        // Create two JMS session objects
        TopicSession pubSession = connection.createTopicSession(
            false, Session.AUTO_ACKNOWLEDGE);        
        TopicSession subSession = connection.createTopicSession(
            false, Session.AUTO_ACKNOWLEDGE);

        // Look up a JMS topic
        Topic chatTopic = (Topic)ctx.lookup(topicName);

        // Create a JMS publisher and subscriber
        TopicPublisher publisher = 
            pubSession.createPublisher(chatTopic);
        TopicSubscriber subscriber = 
            subSession.createSubscriber(chatTopic, null, false);

        // Set a JMS message listener
        subscriber.setMessageListener(this);

        // Intialize the Chat application variables
        this.connection = connection;
        this.pubSession = pubSession;
        this.publisher = publisher;
        this.username = username;

        // Start the JMS connection; allows messages to be delivered
        connection.start( );
    }

    /* Receive Messages From Topic Subscriber */
    public void onMessage(Message message) {
        try {
            TextMessage textMessage = (TextMessage) message;
            String text = textMessage.getText( );
            System.out.println(text);
        } catch (JMSException jmse){ jmse.printStackTrace( ); }
    }

    /* Create and Send Message Using Publisher */
    protected void writeMessage(String text) throws JMSException {
        TextMessage message = pubSession.createTextMessage( );
        message.setText(username+": "+text);
        publisher.publish(message);
    }

    /* Close the JMS Connection */
    public void close( ) throws JMSException {
        connection.close( );
    }

    /* Run the Chat Client */
    public static void main(String [] args){
        try{

            Chat chat = new Chat("TopicCF","topic1","userName1");

            // Read from command line
            BufferedReader commandLine = new 
              java.io.BufferedReader(new InputStreamReader(System.in));

            // Loop until the word "exit" is typed
            while(true){
                String s = commandLine.readLine( );
                if (s.equalsIgnoreCase("exit")){
                    chat.close( ); // close down connection
                    System.exit(0);// exit program
                } else 
                    chat.writeMessage(s);
            }
        } catch (Exception e){ e.printStackTrace( ); }
    }
}

5.打开多个console，运行main函数，分别监视不同main方法的输入输出即可

6.持久订阅者和非持久订阅者：持久订阅者无论活动与否都会收到该主题的消息。这是使用保存并转发机制保证的，持久订阅者通过createDurableSubscriber方法创建，创建持久订阅者时，需要考虑消息的时效性（过期的消息没有什么用）和消息消耗的存储容量。

7.动态订阅者和受管订阅者：在配置文件或管理界面中定义的持久订阅者称为受管订阅者，在运行时动态定义的称为动态持久定义者

8.取消持久订阅者：

subscriber.close();
subSession.unsubscribe(s);