Spring Boot文档阅读笔记-对Messaging with RabbitMQ解析-蒲公英云

此篇教程以Rabbitmq作为消息队列服务端，使用Spring Boot产生和发布消息。

使用Spring AMQP的RabbitTemplate发布消息，使用MessageListenerAdapter订阅消息。

其中对应的Maven如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.0</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>cn.it1995</groupId>
    <artifactId>demo</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>demo</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.amqp</groupId>
            <artifactId>spring-rabbit-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.amqp</groupId>
            <artifactId>spring-amqp</artifactId>
            <version>2.3.1</version>
            <scope>compile</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.amqp</groupId>
            <artifactId>spring-rabbit</artifactId>
            <version>2.3.1</version>
            <scope>compile</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

下面是创建接受者，获取发布者的发布的消息：

package cn.it1995.demo;
import org.springframework.stereotype.Component;
import java.util.concurrent.CountDownLatch;
@Component
public class Receiver {
    private CountDownLatch latch = new CountDownLatch(1);
    public void receiveMessage(String message){
        System.out.println("Received <" + message + ">");
        latch.countDown();
    }
    public CountDownLatch getLatch(){
        return latch;
    }
}

这个Receiver是POJO类，这里的POJO是指没有带有业务处理的类，当注册后，就能在任意的地方进使用。

CountDownLatch，里面会有一个接收消息的信号。

注册监听者以及发送消息

使用Spring AMQP的RabbitTemplate提供的函数用于接收消息，逻辑如下：

配置消息监听者容器；

2.声明队列，交换机对其都进行绑定；

3.配置发送者组建，使得监听者能接收到。

代码如下：

package cn.it1995.demo;
import org.springframework.amqp.core.Binding;
import org.springframework.amqp.core.BindingBuilder;
import org.springframework.amqp.core.Queue;
import org.springframework.amqp.core.TopicExchange;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
@SpringBootApplication
public class DemoApplication {
    static final String topicExchangeName = "spring-boot-exchange";
    static final String queueName = "spring-boot";
    @Bean
    Queue queue(){
        return new Queue(queueName, false);
    }
    @Bean
    TopicExchange exchange(){
        return new TopicExchange(topicExchangeName);
    }
    @Bean
    Binding binding(Queue queue, TopicExchange exchange){
        return BindingBuilder.bind(queue).to(exchange).with("foo.bar.#");
    }
    @Bean
    SimpleMessageListenerContainer container(ConnectionFactory connectionFactory,
                                             MessageListenerAdapter listenerAdapter){
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        container.setConnectionFactory(connectionFactory);
        container.setQueueNames(queueName);
        container.setMessageListener(listenerAdapter);
        return container;
    }
    @Bean
    MessageListenerAdapter listenerAdapter(Receiver receiver){
        return new MessageListenerAdapter(receiver, "receiveMessage");
    }
    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

listenerAdapter()方法将消息监听者注册到容器中（默认是在container()）。

queue()方法创建了AMQP的队列。exchange()方法创建了topic交换机。

binding()方法将其进行绑定。

发送测试数据到Rabbitmq

package cn.it1995.demo;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
import java.util.concurrent.TimeUnit;
@Component
public class Runner implements CommandLineRunner {
    private final RabbitTemplate rabbitTemplate;
    private final Receiver receiver;
    public Runner(Receiver receiver, RabbitTemplate rabbitTemplate){
        this.receiver = receiver;
        this.rabbitTemplate = rabbitTemplate;
    }
    @Override
    public void run(String... args) throws Exception {
        System.out.println("Sending message ...");
        rabbitTemplate.convertAndSend(DemoApplication.topicExchangeName, "foo.bar.baz", "Hello from RabbitMQ!");
        receiver.getLatch().await(10000, TimeUnit.MILLISECONDS);
    }
}

项目的application.properties如下：

spring.rabbitmq.host=122.xxx.xxx.xxx
spring.rabbitmq.port=5672
spring.rabbitmq.username=xxxx
spring.rabbitmq.password=xxxxxxx
spring.rabbitmq.virtual-host=/xxxxx