第三章 ActiveMQ模拟股票价格涨跌（发布/订阅模式）

概述：模拟某个用户订阅某些股票，然后向对应用户推送股票的价格

这个例子来自于ActiveMQ In Action源码中

1、先决条件：

本来只需要maven就可以，但为了方便采用IDE工具Eclipse

2、执行顺序

• 启动ActiveMQ
• 运行Consumer 类
• 运行Publisher类

3、具体步骤

3.1、启动ActiveMQ

注意：不要关闭这个窗口

2、运行Comsumer类

这里需要一个监听类，监听发布者的消息

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) {    //消费监听器只有一个方法onMessage
		try {
			MapMessage map = (MapMessage)message;   //表示Message本身是map
			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" );   //表示格式数据#表示没有为空，0表示没有赋值为0，例如54.97944 最后格式化54.97
			System.out.println(stock + "\t" + df.format(price) + "\t" + df.format(offer) + "\t" + (up?"up":"down"));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

}

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;  //transient表示序列化时候不会包含在对象中
    private transient Connection connection;
    private transient Session session;
    
    public Consumer() throws JMSException {
    	factory = new ActiveMQConnectionFactory(brokerURL);   //创建activeMq连接工厂类  
    	connection = factory.createConnection();   //获取连接实例
        connection.start();                        //开始连接
        session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);    //为连接创建一个会话
    }
    
    public void close() throws JMSException {   //创建关闭动作
        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);  //创建一个感兴趣的话题
    		MessageConsumer messageConsumer = consumer.getSession().createConsumer(destination);   //根据根据感兴趣话题获取消息消费对象
    		messageConsumer.setMessageListener(new Listener());  //为消费绑定对应监听器
    	}
    }
	
	public Session getSession() {
		return session;
	}

}

控制台没有任何输出

3.2运行Publisher类

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>();  //并发map
    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();
        connection.start();
        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); //封装发送数据
            }
            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()); // 0 1 2
            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) {  //随机改变价格
        double percentChange = (2 * Math.random() * MAX_DELTA_PERCENT) - MAX_DELTA_PERCENT;

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

}

这个也要重复Consumer操作，为main方法传递同样的值（其实这些值就是生成topic原材料，发布者会将消息发送这个topic上，消费者会监听这个topic的信息）

Publisher部分日志

Comsumer部分日志：

参考《ActiveMQ In Action》书