ActiveMQ学习教程（一）——安装与示例

背景：ActiveMQ 是Apache出品，最流行的，能力强劲的开源消息总线。
选择ActiveMQ作为JMS的入门学习中间件，是因为其拥有以下优点

1.多种语言和协议编写客户端。语言: Java, C, C++, C#, Ruby, Perl, Python, PHP。应用协议: OpenWire,Stomp REST,WS Notification,XMPP,AMQP
2.完全支持JMS1.1和J2EE 1.4规范 (持久化,XA消息,事务)
3.对Spring的支持,ActiveMQ可以很容易内嵌到使用Spring的系统里面去,而且也支持Spring2.0的特性
4.完全支持JMS1.1和J2EE 1.4规范 (持久化,XA消息,事务)
5.通过了常见J2EE服务器(如 Geronimo,JBoss 4, GlassFish,WebLogic)的测试,其中通过JCA 1.5 resource adaptors的配置,可以让ActiveMQ可以自动的部署到任何兼容J2EE 1.4 商业服务器上
6.支持多种传送协议:in-VM,TCP,SSL,NIO,UDP,JGroups,JXTA
7.从设计上保证了高性能的集群,客户端-服务器,点对点
8.支持Ajax
9.支持与Axis的整合
10.可以很容易得调用内嵌JMS provider,进行测试

学会了ActiveMQ之后，其它供应商的MQ也可以在短时间内快速上手。

安装：
ActiveMQ（本文简称MQ）要求JDK1.5以上，推荐1.6以上版本。还没安装JDK的朋友，请先安装，在此不赘诉了。
安装完JDK后，从 http://activemq.apache.org/download.html下载MQ的最新版本，本教程使用版本为5.5。
解压后，可以看到MQ目录下有以下文件和目录

activemq-all-5.5.0.jar:所有MQ JAR包的集合，用于用户系统调用
bin:其中包含MQ的启动脚本
conf:包含MQ的所有配置文件
data:日志文件及持久性消息数据
example:MQ的示例
lib:MQ运行所需的所有Lib
webapps:MQ的Web控制台及一些相关的DEMO

启动MQ：
双击bin目录下的activemq.bat文件即可启动MQ


第一个示例：

新建一个JAVA工程，引用activemq-all-5.5.0.jar，SLFAPI其及对应版本LOG4J的JAR包（懒的上网找的到附件里下载）

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();
		}
	}

}

先运行Consumer.java, 输入参数ORCL，然后运行Publisher.java，输入参数ORCL，
就可以看到Publisher在发送消息，Consumer在接收消息了。
（不知道怎么在ECLIPSE里带参数运行程序的，请自行GOOGLE。）
好了，MQ的安装与第一个示例程序的介绍就到此为止了。

下一节将介绍JMS的一些概念以帮助我们进行后续的学习。