RabbitMQ：MessageConverter訊息轉換器-有解無憂

pom.xml：

<?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>2.6.2</version>
    </parent>

    <packaging>jar</packaging>

    <groupId>com.kaven</groupId>
    <artifactId>springboot</artifactId>
    <version>0.0.1-SNAPSHOT</version>

    <name>springboot</name>
    <description>springboot</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>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-amqp</artifactId>
        </dependency>
        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

application.properties：

spring.rabbitmq.host=192.168.1.9
spring.rabbitmq.port=5672
spring.rabbitmq.username=admin
spring.rabbitmq.password=admin
spring.rabbitmq.virtualHost=/
spring.rabbitmq.exchange=""
spring.rabbitmq.routingKey=kaven
spring.rabbitmq.queue=kaven

RabbitMQProperties類（RabbitMQ的引數類）：

package com.kaven.springboot.rabbitmq;

import lombok.Getter;
import lombok.Setter;
import org.springframework.boot.context.properties.ConfigurationProperties;

@ConfigurationProperties(prefix = "spring.rabbitmq")
@Setter
@Getter
public class RabbitMQProperties {

    private String host;
    private int port;
    private String username;
    private String password;
    private String exchange;
    private String queue;
    private String routingKey;
    private String virtualHost;
}

User類（訊息負載的物體類）：

package com.kaven.springboot.rabbitmq;

import lombok.AllArgsConstructor;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;

@Setter
@Getter
@ToString
@AllArgsConstructor
public class User {
    private String username;
    private String password;
    private String code;
}

Json2UserMessageConverter類（訊息轉換器，將json資料轉換成User物件，json資料由訊息體的byte[]生成）：

package com.kaven.springboot.rabbitmq;

import com.google.gson.Gson;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.amqp.support.converter.MessageConversionException;
import org.springframework.amqp.support.converter.MessageConverter;
import org.springframework.stereotype.Component;

import java.nio.charset.StandardCharsets;

@Component
public class Json2UserMessageConverter implements MessageConverter {

    private static final Gson GSON = new Gson();

    @Override
    public Message toMessage(Object object, MessageProperties messageProperties) throws MessageConversionException {
        return new Message(GSON.toJson(object).getBytes(StandardCharsets.UTF_8));
    }

    @Override
    public Object fromMessage(Message message) throws MessageConversionException {
        return GSON.fromJson(new String(message.getBody(), StandardCharsets.UTF_8), User.class);
    }
}

CustomizeMessageListener類（自定義訊息監聽器）：

package com.kaven.springboot.rabbitmq;

import org.springframework.stereotype.Component;

@Component
public class CustomizeMessageListener {
    public void customizeHandleMessage(User user) {
        System.out.printf("處理用戶資料: %s\n", user);
    }
}

RabbitMQConfig類（定義RabbitMQ組件的配置類）：

package com.kaven.springboot.rabbitmq;

import org.springframework.amqp.core.*;
import org.springframework.amqp.rabbit.connection.CachingConnectionFactory;
import org.springframework.amqp.rabbit.connection.ConnectionFactory;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.amqp.rabbit.listener.SimpleMessageListenerContainer;
import org.springframework.amqp.rabbit.listener.adapter.MessageListenerAdapter;
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 javax.annotation.Resource;

@Configuration
public class RabbitMQConfig {

    @Resource
    private RabbitMQProperties properties;

    @Bean
    public ConnectionFactory connectionFactory() {
        CachingConnectionFactory connectionFactory = new CachingConnectionFactory(properties.getHost(), properties.getPort());
        connectionFactory.setUsername(properties.getUsername());
        connectionFactory.setPassword(properties.getPassword());
        connectionFactory.setVirtualHost(properties.getVirtualHost());
        return connectionFactory;
    }

    @Bean
    @Scope(ConfigurableBeanFactory.SCOPE_PROTOTYPE)
    //必須是prototype型別
    public RabbitTemplate rabbitTemplate(ConnectionFactory connectionFactory) {
        return new RabbitTemplate(connectionFactory);
    }

    @Bean
    public SimpleMessageListenerContainer simpleMessageListenerContainer(ConnectionFactory connectionFactory,
                                                                         CustomizeMessageListener delegate,
                                                                         Json2UserMessageConverter messageConverter) {
        SimpleMessageListenerContainer container = new SimpleMessageListenerContainer();
        // 設定連接工廠
        container.setConnectionFactory(connectionFactory);
        // 指定要創建的并發消費者數量
        // 默認值為1
        container.setConcurrentConsumers(3);
        // 設定消費者數量的上限
        // 默認為concurrentConsumers
        // 消費者將按需添加
        // 不能小于concurrentConsumers
        container.setMaxConcurrentConsumers(5);
        // 設定要從中接收訊息的佇列名稱
        // 引數為String... queueName
        container.setQueueNames(properties.getQueue());
        // 控制容器在訊息確認方面的行為
        // 自動確認
        // 如果手動確認
        // 可以使用ChannelAwareMessageListener訊息監聽器
        container.setAcknowledgeMode(AcknowledgeMode.AUTO);
        // 告訴代理在單個請求中向每個消費者發送多少條訊息
        // 通常可以將其設定得相當高以提高吞吐量
        container.setPrefetchCount(3);

        // 創建配接器
        MessageListenerAdapter adapter = new MessageListenerAdapter();
        // 設定委托物件
        adapter.setDelegate(delegate);
        // 設定默認的監聽方法名稱
        adapter.setDefaultListenerMethod("customizeHandleMessage");
        // 設定訊息轉換器
        adapter.setMessageConverter(messageConverter);

        // 設定MessageListener(訊息監聽器)
        container.setMessageListener(adapter);
        return container;
    }

    @Bean
    public DirectExchange exchange() {
        return new DirectExchange(properties.getExchange());
    }

    @Bean
    public Queue queue() {
        //佇列持久
        return new Queue(properties.getQueue(), true);
    }

    @Bean
    public Binding binding() {
        return BindingBuilder.bind(queue()).to(exchange()).with(properties.getRoutingKey());
    }
}

Producer類（用于發布訊息）：

package com.kaven.springboot.rabbitmq;

import com.google.gson.Gson;
import org.springframework.amqp.core.Message;
import org.springframework.amqp.core.MessageProperties;
import org.springframework.amqp.rabbit.connection.CorrelationData;
import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.nio.charset.StandardCharsets;
import java.util.UUID;

@Component
public class Producer {

    private final RabbitTemplate rabbitTemplate;
    private static final Gson GSON = new Gson();

    @Resource
    private RabbitMQProperties properties;

    @Autowired
    public Producer(RabbitTemplate rabbitTemplate) {
        this.rabbitTemplate = rabbitTemplate;
    }

    public void sendMsg(User user) {
        CorrelationData correlationId = new CorrelationData(UUID.randomUUID().toString());
        MessageProperties messageProperties = new MessageProperties();
        messageProperties.setExpiration("10000");
        Message message = new Message(GSON.toJson(user).getBytes(StandardCharsets.UTF_8), messageProperties);
        rabbitTemplate.send(properties.getExchange(), properties.getRoutingKey(), message, correlationId);
    }
}

ProducerController類（用于發布訊息的介面）：

package com.kaven.springboot.rabbitmq;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
public class ProducerController {

    @Resource
    private Producer producer;

    @GetMapping("/send")
    public String send(User user) {
        System.out.println(user);
        producer.sendMsg(user);
        return "資料發送成功";
    }
}

啟動類：

package com.kaven.springboot;

import com.kaven.springboot.rabbitmq.RabbitMQProperties;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.ConfigurationPropertiesScan;

@SpringBootApplication
@ConfigurationPropertiesScan(basePackageClasses = {RabbitMQProperties.class})
public class SpringbootApplication {
    public static void main(String[] args) {
        SpringApplication application = new SpringApplication(SpringbootApplication.class);
        application.run(args);
    }
}

啟動應用，使用Postman請求介面，
在這里插入圖片描述
控制臺輸出：

User(username=kaven, password=itkaven, code=908767)
處理用戶資料: User(username=kaven, password=itkaven, code=908767)

輸出符合預期，訊息轉換器的作用就是當SimpleMessageListenerContainer并發消費時，將獲取的訊息轉換成想要的資料型別（將訊息體中的byte[]轉換成json，再將json轉換成User物件，這里不討論Json2UserMessageConverter類名是否合適），比如這里的User物件，之后訊息監聽器接收的就是進行了轉換的資料型別，即直接處理User物件，單一職責原則，因此生產者發布的資料也應該從User物件轉換成json，最后轉換成byte[]型別，MessageConverter訊息轉換器就介紹到這里，如果博主有說錯的地方或者大家有不同的見解，歡迎大家評論補充，

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