JMS實戰

 

JMS實戰

.JMS介紹 
    JMS源於企業應用對於消息中間件的需求，使應用程序可以通過消息進行異步處理而互不影響。Sun公司和它的合作伙伴設計的JMS API定義了一組公共的應用程序接口和相應語法，使得Java程序能夠和其他消息組件進行通信。JMS有四個組成部分：JMS服務提供者、消息管理對象、消息的生產者消費者和消息本身。 
1)JMS服務提供者實現消息隊列和通知，同時實現消息管理的API。JMS已經是J2EE API的一部分，J2EE服務器都提供JMS服務。 
2) 消息管理對象提供對消息進行操作的API。JMS API中有兩個消息管理對象：創建jms連接使用的工廠（ConnectionFactory）和目的地（Destination），根據消息的消費方式的不同ConnectionFactory可以分爲QueueConnectionFactory和TopicConnectionFactory，目的地（Destination）可以分爲隊列（Queue）和主題（Topic）兩種。 
3)消息的生產者和消費者。消息的產生由JMS的客戶端完成，JMS服務提供者負責管理這些消息，消息的消費者可以接收消息。消息的生產者可以分爲――點對點消息發佈者（P2P）和主題消息發佈者（TopicPublisher）。所以，消息的消費者分爲兩類：主題消息的訂閱者（TopicSubscriber)和點對點消息的接收者（queue receiver） 
4)消息。消息是服務提供者和客戶端之間傳遞信息所使用的信息單元。JMS消息由以下三部分組成： 
　　消息頭（header）――JMS消息頭包含了許多字段，它們是消息發送後由JMS提供者或消息發送者產生，用來表示消息、設置優先權和失效時間等等，並且爲消息確定路由。 
　　屬性（property）――用來添加刪除消息頭以外的附加信息。 
　　消息體（body）――JMS中定義了5種消息體：ByteMessage、MapMessage、ObjectMessage、StreamMessage和TextMessage。 

2.Messages 通信方式 
上面提到JMS通信方式分爲點對點通信和發佈/訂閱方式 
1)點對點方式（point-to-point） 
   點對點的消息發送方式主要建立在 Message Queue,Sender,reciever上，Message Queue 存貯消息，Sneder 發送消息，receive接收消息.具體點就是Sender Client發送Message Queue ,而 receiver Cliernt從Queue中接收消息和"發送消息已接受"到Quere,確認消息接收。消息發送客戶端與接收客戶端沒有時間上的依賴，發送客戶端可以在任何時刻發送信息到Queue，而不需要知道接收客戶端是不是在運行 
2)發佈/訂閱 方式（publish/subscriber Messaging） 
    發佈/訂閱方式用於多接收客戶端的方式.作爲發佈訂閱的方式，可能存在多個接收客戶端，並且接收端客戶端與發送客戶端存在時間上的依賴。一個接收端只能接收他創建以後發送客戶端發送的信息。作爲subscriber ,在接收消息時有兩種方法，destination的receive方法，和實現message listener 接口的onMessage 方法。 

3.爲什麼選用ActiveMQ 
   1）ActiveMQ是一個開放源碼 
   2）基於Apache 2.0 licenced 發佈並實現了JMS 1.1。 
   3）ActiveMQ現在已經和作爲很多項目的異步消息通信核心了 
   4）在很多中小型項目中採用ActiveMQ+SPRING+TOMCAT開發模式。 

4.編程模式 
4.1消息產生者向JMS發送消息的步驟 
(1)創建連接使用的工廠類JMS ConnectionFactory 
(2)使用管理對象JMS ConnectionFactory建立連接Connection 
(3)使用連接Connection 建立會話Session 
(4)使用會話Session和管理對象Destination創建消息生產者MessageSender 
(5)使用消息生產者MessageSender發送消息 
4.2消息消費者從JMS接受消息的步驟 
(1)創建連接使用的工廠類JMS ConnectionFactory 
(2)使用管理對象JMS ConnectionFactory建立連接Connection 
(3)使用連接Connection 建立會話Session 
(4)使用會話Session和管理對象Destination創建消息消費者MessageReceiver 
(5)使用消息消費者MessageReceiver接受消息，需要用setMessageListener將MessageListener接口綁定到MessageReceiver 
消息消費者必須實現了MessageListener接口，需要定義onMessage事件方法。 

5.ActiveMQ運行 
ActiveMQ5.0版本默認啓動時，啓動了內置的jetty服務器，提供一個demo應用和用於監控ActiveMQ的admin應用。運行%activemq_home%bin/目錄下的 activemq.bat , 之後你會看見如下一段話表示啓動成功。 
打開http://localhost:8161/admin/queues.jsp ，可以查看相應的queue中是否有消息

 

服務端TopicPublisher.java

6 可用的例子

客戶端：TopicListener.java

public class TopicListener implements MessageListener {

    private Connection connection;
    private MessageProducer producer;
    private Session session;
    private int count;
    private long start;
    private Topic topic;
    private Topic control;

    private String url = "tcp://localhost:61616";

    private static MyConsumerFrame frame= new MyConsumerFrame();;

    private static Long countMsg = 1L;

    public static void main(String[] argv) throws Exception {

        TopicListener l = new TopicListener();
        String[] unknown = CommandLineSupport.setOptions(l, argv);
        if (unknown.length > 0) {
            System.out.println("Unknown options: " + Arrays.toString(unknown));
            System.exit(-1);
        }
        l.run();
    }

    public void run() throws JMSException {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(url);
        connection = factory.createConnection();
        session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
        topic = session.createTopic("topictest.messages");
        control = session.createTopic("topictest.control");

        MessageConsumer consumer = session.createConsumer(topic);
        consumer.setMessageListener(this);

        connection.start();

        producer = session.createProducer(control);
        System.out.println("Waiting for messages...");
    }

    private static boolean checkText(Message m, String s) {
        try {
            return m instanceof TextMessage && ((TextMessage)m).getText().equals(s);
        } catch (JMSException e) {
            e.printStackTrace(System.out);
            return false;
        }
    }

    public void onMessage(Message message) {
        if (message instanceof ExitRecord) {
            System.out.println("___________________Object Message!");
            ExitRecord record = (ExitRecord)message;
            Long msgCpuId = record.getCpucardId();
            frame.getTableModle().addRow(new String[]{String.valueOf(countMsg++), String.valueOf(msgCpuId)});
        }

        if (checkText(message, "SHUTDOWN")) {

            try {
                connection.close();
            } catch (Exception e) {
                e.printStackTrace(System.out);
            }

        } else if (checkText(message, "REPORT")) {
            // send a report:
            try {
                long time = System.currentTimeMillis() - start;
                String msg = "Received " + count + " in " + time + "ms";
                producer.send(session.createTextMessage(msg));
            } catch (Exception e) {
                e.printStackTrace(System.out);
            }
            count = 0;

        } else {

            if (count == 0) {
                start = System.currentTimeMillis();
            }

            if (++count % 1000 == 0) {
                System.out.println("Received " + count + " messages.");
            }
        }
    }

    public void setUrl(String url) {
        this.url = url;
    }

}

public class TopicPublisher implements MessageListener {

    private static final char[] DATA = "abcdefghijklmnopqrstuvwxyz".toCharArray();

    private final Object mutex = new Object();
    private Connection connection;
    private Session session;
    private MessageProducer publisher;
    private Topic topic;
    private Topic control;

    private String url = "tcp://localhost:61616";
    private int size = 256;
    private int subscribers = 1;
    private int remaining;
    private int messages = 10000;
    private long delay;
    private int batch = 2000;

    private byte[] payload;

    public static void main(String[] argv) throws Exception {
        TopicPublisher p = new TopicPublisher();
        String[] unknown = CommandLineSupport.setOptions(p, argv);
        if (unknown.length > 0) {
            System.out.println("Unknown options: " + Arrays.toString(unknown));
            System.exit(-1);
        }
        p.run();
    }

    private void run() throws Exception {
        ActiveMQConnectionFactory factory = new ActiveMQConnectionFactory(url);
        connection = factory.createConnection();
        session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
        topic = session.createTopic("topictest.messages");
        control = session.createTopic("topictest.control");

        publisher = session.createProducer(topic);
        publisher.setDeliveryMode(DeliveryMode.NON_PERSISTENT);

        payload = new byte[size];
        for (int i = 0; i < size; i++) {
            payload[i] = (byte)DATA[i % DATA.length];
        }

        session.createConsumer(control).setMessageListener(this);
        connection.start();

        long[] times = new long[batch];
        for (int i = 0; i < batch; i++) {
            if (i > 0) {
                Thread.sleep(delay * 1000);
            }
            times[i] = batch(messages);
            System.out.println("Batch " + (i + 1) + " of " + batch + " completed in " + times[i] + " ms.");
        }

        long min = min(times);
        long max = max(times);
        System.out.println("min: " + min + ", max: " + max + " avg: " + avg(times, min, max));

        // request shutdown
        publisher.send(session.createTextMessage("SHUTDOWN"));

        connection.stop();
        connection.close();
    }

    private long batch(int msgCount) throws Exception {
        long start = System.currentTimeMillis();
        remaining = subscribers;
        publish();
        waitForCompletion();
        return System.currentTimeMillis() - start;
    }

    private void publish() throws Exception {

        // send events
        BytesMessage msg = session.createBytesMessage();
        msg.writeBytes(payload);
        for (int i = 0; i < messages; i++) {
            publisher.send(msg);
            if ((i + 1) % 1000 == 0) {
                System.out.println("Sent " + (i + 1) + " messages");
            }
        }

        // request report
        publisher.send(session.createTextMessage("REPORT"));
    }

    private void waitForCompletion() throws Exception {
        System.out.println("Waiting for completion...");
        synchronized (mutex) {
            while (remaining > 0) {
                mutex.wait();
            }
        }
    }

    public void onMessage(Message message) {
        synchronized (mutex) {
            System.out.println("Received report " + getReport(message) + " " + --remaining + " remaining");
            if (remaining == 0) {
                mutex.notify();
            }
        }
    }

    Object getReport(Message m) {
        try {
            return ((TextMessage)m).getText();
        } catch (JMSException e) {
            e.printStackTrace(System.out);
            return e.toString();
        }
    }

    static long min(long[] times) {
        long min = times.length > 0 ? times[0] : 0;
        for (int i = 0; i < times.length; i++) {
            min = Math.min(min, times[i]);
        }
        return min;
    }

    static long max(long[] times) {
        long max = times.length > 0 ? times[0] : 0;
        for (int i = 0; i < times.length; i++) {
            max = Math.max(max, times[i]);
        }
        return max;
    }

    static long avg(long[] times, long min, long max) {
        long sum = 0;
        for (int i = 0; i < times.length; i++) {
            sum += times[i];
        }
        sum -= min;
        sum -= max;
        return sum / times.length - 2;
    }

    public void setBatch(int batch) {
        this.batch = batch;
    }

    public void setDelay(long delay) {
        this.delay = delay;
    }

    public void setMessages(int messages) {
        this.messages = messages;
    }

    public void setSize(int size) {
        this.size = size;
    }

    public void setSubscribers(int subscribers) {
        this.subscribers = subscribers;
    }

    public void setUrl(String url) {
        this.url = url;
    }
}