RabbitMQ是一种我们经常使用的消息中间件，通过RabbitMQ可以帮助我们实现异步、削峰的目的。
今天这篇，我们来看看Spring Boot是如何集成RabbitMQ，发送消息和消费消息的。同时我们介绍下死信队列。
集成RabbitMQ
集成RabbitMQ只需要如下几步即可
1、添加maven依赖
<!--rabbitmq--><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-amqp</artifactId></dependency>
2、添加配置文件application.yaml
在application.yaml添加配置内容如下
spring: rabbitmq: host: 192.168.1.161 port: 5672 username: guest password: guest cache: channel: size: 10 listener: type: simple simple: acknowledge-mode: auto concurrency: 5 default-requeue-rejected: true max-concurrency: 100 retry: enabled: true # initial-interval: 1000ms max-attempts: 3 # max-interval: 1000ms multiplier: 1 stateless: true # publisher-confirms: true
注意：
这里最基本的配置只需要配置host,port,username和password四个属性即可
其他属性都有各自的含义，比如retry是用于配置重试策略的，acknowledge-mode是配置消息接收确认机制的。
3、编写配置类
编写RabbitConfig配置类，采用Java Configuration的方式配置RabbitTemplate、Exchange和Queue等信息，具体如下所示
package com.jackie.springbootdemo.config;import org.springframework.amqp.core.*;import org.springframework.amqp.rabbit.config.SimpleRabbitListenerContainerFactory;import org.springframework.amqp.rabbit.connection.ConnectionFactory;import org.springframework.amqp.rabbit.core.RabbitTemplate;import org.springframework.amqp.support.converter.Jackson2JsonMessageConverter;import org.springframework.beans.factory.InitializingBean;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.beans.factory.annotation.Qualifier;import org.springframework.beans.factory.annotation.Value;import org.springframework.beans.factory.config.ConfigurableBeanFactory;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.context.annotation.Scope;import java.util.HashMap;import java.util.Map;@Configuration public class RabbitMQConfig implements InitializingBean { @Autowired
SimpleRabbitListenerContainerFactory simpleRabbitListenerContainerFactory; @Override
public void afterPropertiesSet() throws Exception {
simpleRabbitListenerContainerFactory.setMessageConverter(new Jackson2JsonMessageConverter());
} @Bean("jackson2JsonMessageConverter") public Jackson2JsonMessageConverter jackson2JsonMessageConverter(ConnectionFactory connectionFactory) { return new Jackson2JsonMessageConverter();
} @Bean("rabbitTemplate") @Scope(ConfigurableBeanFactory.SCOPE_SINGLETON) public RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory,
@Qualifier("jackson2JsonMessageConverter") Jackson2JsonMessageConverter jackson2JsonMessageConverter) {
RabbitTemplate template = new RabbitTemplate(connectionFactory);
template.setMessageConverter(new Jackson2JsonMessageConverter()); return template;
} // --------------------- 声明队列 ------------------------
@Bean
public Queue demoQueue() { return new Queue("demo_queue");
} // --------------------- 声明exchange ------------------------ @Bean
public DirectExchange demoExchange() { return new DirectExchange("demo_exchange");
} // --------------------- 队列绑定 ------------------------
@Bean
public Binding bindingAlbumItemCreatedQueue(DirectExchange demoExchange,
Queue demoQueue) { return BindingBuilder.bind(demoQueue).to(demoExchange).with("100");
} }注意
这里声明了Direct模式的Exchange，声明一个Queue，并通过routing-key为100将demo_queue绑定到demo_exchange，这样demo_queue就可以接收到demo_exchange发送的消息了。
4、编写消息发送类
package com.jackie.springbootdemo.message;import org.springframework.amqp.rabbit.core.RabbitTemplate;import org.springframework.amqp.rabbit.support.CorrelationData;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.stereotype.Component;@Component public class Sender implements RabbitTemplate.ConfirmCallback { private RabbitTemplate rabbitTemplate; /**
* 构造方法注入 */ @Autowired
public Sender(RabbitTemplate rabbitTemplate) { this.rabbitTemplate = rabbitTemplate;
rabbitTemplate.setConfirmCallback(this); //rabbitTemplate如果为单例的话，那回调就是最后设置的内容
} public void sendMsg(String content) {
rabbitTemplate.convertAndSend("demo_exchange", "100", content);
} /**
* 回调 */ @Override
public void confirm(CorrelationData correlationData, boolean ack, String cause) {
System.out.println(" 回调id:" + correlationData); if (ack) {
System.out.println("消息成功消费");
} else {
System.out.println("消息消费失败:" + cause);
}
} }注意
发送内容content，路由到routing-key为100上，则我们就可以在demo_queue队列中看到发送的消息内容了
confirm函数是回调函数，这里因为没有消费者，且acknoledge-mode是auto(其他两种值分别是none和manual)，所以ack是false。
5、编写发送消息测试类
package com.jackie.springbootdemo;import com.jackie.springbootdemo.message.Sender;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.test.context.junit4.SpringRunner;import org.springframework.test.context.web.WebAppConfiguration;
@RunWith(SpringRunner.class) @SpringBootTest(classes = SpringbootDemoApplication.class) @WebAppConfiguration public class RabbitApplicationTests { @Autowired
Sender sender;
@Test
public void contextLoads() throws Exception { sender.sendMsg("test");
} }运行该测试类，我们可以看到如下结果
image
6、编写消息消费类
package com.jackie.springbootdemo.message;import org.springframework.amqp.rabbit.annotation.RabbitListener;import org.springframework.stereotype.Component;
@Component public class Receiver { @RabbitListener(queues = "demo_queue")
public void created(String message) { System.out.println("orignal message: " + message);
} }注意
消息消费类也非常简单，添加注解@RabbitListener，指定要监听的队列名称即可
除了注解@RabbitListener，我们经常还能看到@RabbitHandler，这两个注解可以配合起来使用。
@RabbitListener 标注在类上面表示当有收到消息的时候，就交给 @RabbitHandler 的方法处理，具体使用哪个方法处理，根据 MessageConverter 转换后的参数类型，形如
@Component @RabbitListener(queues = "demo_queue") public class Receiver { @RabbitHandler public void processMessage1(String message) {
System.out.println(message);
} @RabbitHandler
public void processMessage2(byte[] message) {
System.out.println(new String(message));
} }
作者：Jackie_Zheng
链接：https://www.jianshu.com/p/f20ed49969fc
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