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