消息队列应用场景

    异步处理，应用解耦，流量削锋和消息通讯四个场景

异步处理：

    场景说明：用户注册后，需要发注册邮件和注册短信

应用解耦：

    场景说明：用户下单后，订单系统需要通知库存系统

流量削锋:

    应用场景：秒杀活动，一般会因为流量过大，导致流量暴增，应用容易挂掉.

        1、用户的请求，服务器接收后，首先写入消息队列。假如消息队列长度超过最大数量，则直接抛弃用户请求或跳转到错误页面

        2、秒杀业务根据消息队列中的请求信息，再做后续处理

日志处理:

    应用场景：日志处理是指将消息队列用在日志处理中，比如Kafka的应用，解决大量日志传输的问题

http://activemq.apache.org/activemq-5158-release.html

tar -zxvf apache-activemq-5.15.-bin.tar.gz

进入目录，运行./bin/activemq start

网址：http://139.199.64.189:8161/
点击:Manage ActiveMQ broker输入默认用户和密码都为:admin

<!-- https://mvnrepository.com/artifact/org.apache.activemq/activemq-core -->

        <dependency>

            <groupId>org.apache.activemq</groupId>

            <artifactId>activemq-core</artifactId>

            <version>5.7.</version>

        </dependency>

package com.activemq.demo.method1;

import javax.jms.Connection;

import javax.jms.ConnectionFactory;

import javax.jms.Destination;

import javax.jms.MessageConsumer;

import javax.jms.Session;

import javax.jms.TextMessage;

import org.apache.activemq.ActiveMQConnectionFactory;

public class JMSConsumer {

    //默认连接用户名

    private static final String USERNAME = "admin";//ActiveMQConnection.DEFAULT_USER;

    //默认连接密码

    private static final String PASSWORD = "admin";//ActiveMQConnection.DEFAULT_PASSWORD;

    //默认连接地址,默认端口为61616

    private static final String BROKERURL = "tcp://ip:61616";//ActiveMQConnection.DEFAULT_BROKER_URL;

    public static void main(String[] args) {

        //连接工厂

        ConnectionFactory connectionFactory;

        //连接

        Connection connection = null;

        //会话,接收或者发送消息的线程

        Session session;

        //消息目的地

        Destination destination;

        //消息的消费者

        MessageConsumer messageConsumer;

        //实例化连接工厂

        connectionFactory = new ActiveMQConnectionFactory(JMSConsumer.USERNAME, JMSConsumer.PASSWORD, JMSConsumer.BROKERURL);

        try {

            //通过工厂获取连接

            connection = connectionFactory.createConnection();

            //启动连接

            connection.start();

            //创建会话

            session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);

            //创建一个连接Hello World!的消息队列

            destination = session.createQueue("Hello World");

            //创建消息的消费者

            messageConsumer = session.createConsumer(destination);

            while(true){

                TextMessage textMessage = (TextMessage) messageConsumer.receive(100000);

                if (textMessage != null) {

                    System.err.println("收到的消息:" + textMessage.getText());

                } else {

                    break;

                }

            }

        } catch (Exception e) {

            e.printStackTrace();

        }

    }

}

package com.activemq.demo.method1;

import javax.jms.Connection;

import javax.jms.ConnectionFactory;

import javax.jms.Destination;

import javax.jms.JMSException;

import javax.jms.MessageProducer;

import javax.jms.Session;

import javax.jms.TextMessage;

import org.apache.activemq.ActiveMQConnectionFactory;

public class JMSProducer {

    //默认连接用户名

    private static final String USERNAME = "admin";//ActiveMQConnection.DEFAULT_USER;

    //默认连接密码

    private static final String PASSWORD = "admin";//ActiveMQConnection.DEFAULT_PASSWORD;

    //默认连接地址，默认端口为61616

    private static final String BROKERURL = "tcp://ip:61616";//ActiveMQConnection.DEFAULT_BROKER_URL;

    //发送的消息数量

    private static final int SENDNUM = 10;

    public static void main(String[] args) {

        //连接工厂

        ConnectionFactory connectionFactory;

        //连接

        Connection connection = null;

        //会话,接收或者发送消息的线程

        Session session;

        //消息的目的地

        Destination destination;

        //消息生产者

        MessageProducer messageProducer;

        //实例化连接工厂

        connectionFactory = new ActiveMQConnectionFactory(JMSProducer.USERNAME, JMSProducer.PASSWORD, JMSProducer.BROKERURL);

        try {

            //通过连接工厂获取连接

            connection = connectionFactory.createConnection();

            //启动连接

            connection.start();

            //创建session

            session = connection.createSession(true, Session.AUTO_ACKNOWLEDGE);

            //创建一个名称为Hello World!的消息队列

            destination = session.createQueue("Hello World");

            //创建消息生产者

            messageProducer = session.createProducer(destination);

            //发送消息

            sendMessage(session,messageProducer);

            session.commit();

        } catch (Exception e) {

            e.printStackTrace();

        } finally{

            if(connection != null){

                try {

                    connection.close();

                } catch (JMSException e) {

                    e.printStackTrace();

                }

            }

        }

    }

    /**

     * 发送消息

     * @param session

     * @param messageProducer 消息生产者

     * @throws Exception

     */

    public static void sendMessage(Session session,MessageProducer messageProducer) throws Exception{

        for (int i = 0; i < JMSProducer.SENDNUM; i++) {

            //创建一条文本消息

            TextMessage message = session.createTextMessage("activemq 发送消息:" + i);

            System.err.println("发送消息:activemq 发送消息:" + i);

            //通过消息生产者发出消息

            messageProducer.send(message);

        }

    }

}

package com.activemq.demo.method2;

import javax.jms.JMSException;

import javax.jms.Message;

import javax.jms.MessageListener;

import javax.jms.TextMessage;

public class MyListener implements MessageListener {

    @Override

    public void onMessage(Message message) {

        try {

            System.out.println("订阅者一收到的消息："+((TextMessage)message).getText());

        } catch (JMSException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

    }

}