ActiveMQ

背景：ActiveMQ 是Apache出品，最流行的，能力強勁的開源消息總線。
選擇ActiveMQ作爲JMS的入門學習中間件，是因爲其擁有以下優點

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  1.多種語言和協議編寫客戶端。語言: Java, C, C++, C#, Ruby, Perl, Python, PHP。應用協議: OpenWire,Stomp REST,WS Notification,XMPP,AMQP
  2.完全支持JMS1.1和J2EE 1.4規範 (持久化,XA消息,事務)
  3.對Spring的支持,ActiveMQ可以很容易內嵌到使用Spring的系統裏面去,而且也支持Spring2.0的特性
  4.完全支持JMS1.1和J2EE 1.4規範 (持久化,XA消息,事務)
  5.通過了常見J2EE服務器(如 Geronimo,JBoss 4, GlassFish,WebLogic)的測試,其中通過JCA 1.5 resource adaptors的配置,可以讓ActiveMQ可以自動的部署到任何兼容J2EE 1.4 商業服務器上
  6.支持多種傳送協議:in-VM,TCP,SSL,NIO,UDP,JGroups,JXTA
  7.從設計上保證了高性能的集羣,客戶端-服務器,點對點
  8.支持Ajax
  9.支持與Axis的整合
  10.可以很容易得調用內嵌JMS provider,進行測試
  

學會了ActiveMQ之後，其它供應商的MQ也可以在短時間內快速上手。

安裝：
ActiveMQ（本文簡稱MQ）要求JDK1.5以上，推薦1.6以上版本。還沒安裝JDK的朋友，請先安裝，在此不贅訴了。
安裝完JDK後，從 http://activemq.apache.org/download.html下載MQ的最新版本，本教程使用版本爲5.5。
解壓後，可以看到MQ目錄下有以下文件和目錄

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activemq-all-5.5.0.jar:所有MQ JAR包的集合，用於用戶系統調用
bin:其中包含MQ的啓動腳本
conf:包含MQ的所有配置文件
data:日誌文件及持久性消息數據
example:MQ的示例
lib:MQ運行所需的所有Lib
webapps:MQ的Web控制檯及一些相關的DEMO


啓動MQ：
雙擊bin目錄下的activemq.bat文件即可啓動MQ


第一個示例：

新建一個JAVA工程，引用activemq-all-5.5.0.jar，SLFAPI其及對應版本LOG4J的JAR包（懶的上網找的到附件裏下載）

Publisher.java

import java.util.Hashtable;
import java.util.Map;

import javax.jms.Connection;
import javax.jms.ConnectionFactory;
import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.MapMessage;
import javax.jms.Message;
import javax.jms.MessageProducer;
import javax.jms.Session;

import org.apache.activemq.ActiveMQConnectionFactory;
import org.apache.activemq.command.ActiveMQMapMessage;

public class Publisher {

    protected int MAX_DELTA_PERCENT = 1;
    protected Map<String, Double> LAST_PRICES = new Hashtable<String, Double>();
    protected static int count = 10;
    protected static int total;

    protected static String brokerURL = "tcp://localhost:61616";
    protected static transient ConnectionFactory factory;
    protected transient Connection connection;
    protected transient Session session;
    protected transient MessageProducer producer;

    public Publisher() throws JMSException {
        factory = new ActiveMQConnectionFactory(brokerURL);
        connection = factory.createConnection();
        try {
        connection.start();
        } catch (JMSException jmse) {
            connection.close();
            throw jmse;
        }
        session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
        producer = session.createProducer(null);
    }

    public void close() throws JMSException {
        if (connection != null) {
            connection.close();
        }
    }

    public static void main(String[] args) throws JMSException {
        Publisher publisher = new Publisher();
        while (total < 1000) {
            for (int i = 0; i < count; i++) {
                publisher.sendMessage(args);
            }
            total += count;
            System.out.println("Published '" + count + "' of '" + total + "' price messages");
            try {
              Thread.sleep(1000);
            } catch (InterruptedException x) {
            }
        }
        publisher.close();
    }

    protected void sendMessage(String[] stocks) throws JMSException {
        int idx = 0;
        while (true) {
            idx = (int)Math.round(stocks.length * Math.random());
            if (idx < stocks.length) {
                break;
            }
        }
        String stock = stocks[idx];
        Destination destination = session.createTopic("STOCKS." + stock);
        Message message = createStockMessage(stock, session);
        System.out.println("Sending: " + ((ActiveMQMapMessage)message).getContentMap() + " on destination: " + destination);
        producer.send(destination, message);
    }

    protected Message createStockMessage(String stock, Session session) throws JMSException {
        Double value = LAST_PRICES.get(stock);
        if (value == null) {
            value = new Double(Math.random() * 100);
        }

        // lets mutate the value by some percentage
        double oldPrice = value.doubleValue();
        value = new Double(mutatePrice(oldPrice));
        LAST_PRICES.put(stock, value);
        double price = value.doubleValue();

        double offer = price * 1.001;

        boolean up = (price > oldPrice);

        MapMessage message = session.createMapMessage();
        message.setString("stock", stock);
        message.setDouble("price", price);
        message.setDouble("offer", offer);
        message.setBoolean("up", up);
        return message;
    }

    protected double mutatePrice(double price) {
        double percentChange = (2 * Math.random() * MAX_DELTA_PERCENT) - MAX_DELTA_PERCENT;

        return price * (100 + percentChange) / 100;
    }

}

Consumer.java

import javax.jms.Connection;
import javax.jms.ConnectionFactory;
import javax.jms.Destination;
import javax.jms.JMSException;
import javax.jms.MessageConsumer;
import javax.jms.Session;

import org.apache.activemq.ActiveMQConnectionFactory;

public class Consumer {

    private static String brokerURL = "tcp://localhost:61616";
    private static transient ConnectionFactory factory;
    private transient Connection connection;
    private transient Session session;

    public Consumer() throws JMSException {
        factory = new ActiveMQConnectionFactory(brokerURL);
        connection = factory.createConnection();
        connection.start();
        session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
    }

    public void close() throws JMSException {
        if (connection != null) {
            connection.close();
        }
    }

    public static void main(String[] args) throws JMSException {
        Consumer consumer = new Consumer();
        for (String stock : args) {
            Destination destination = consumer.getSession().createTopic("STOCKS." + stock);
            MessageConsumer messageConsumer = consumer.getSession().createConsumer(destination);
            messageConsumer.setMessageListener(new Listener());
        }
    }

    public Session getSession() {
        return session;
    }

}

Listener.java

import java.text.DecimalFormat;

import javax.jms.MapMessage;
import javax.jms.Message;
import javax.jms.MessageListener;

public class Listener implements MessageListener {

    public void onMessage(Message message) {
        try {
            MapMessage map = (MapMessage)message;
            String stock = map.getString("stock");
            double price = map.getDouble("price");
            double offer = map.getDouble("offer");
            boolean up = map.getBoolean("up");
            DecimalFormat df = new DecimalFormat( "#,###,###,##0.00" );
            System.out.println(stock + "\t" + df.format(price) + "\t" + df.format(offer) + "\t" + (up?"up":"down"));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

}

先運行Consumer.java, 輸入參數ORCL，然後運行Publisher.java，輸入參數ORCL，
就可以看到Publisher在發送消息，Consumer在接收消息了。
（不知道怎麼在ECLIPSE裏帶參數運行程序的，請自行GOOGLE。）
好了，MQ的安裝與第一個示例程序的介紹就到此爲止了。