RabbitMQ 如何实现延迟队列？

import org.springframework.context.annotation.Configuration;
import org.springframework.amqp.core.*;
import org.springframework.context.annotation.Bean;

/**
 * 延迟交换器和队列
 */
@Configuration
public class DelayedExchangeConfig {
    public static final String EXCHANGE_NAME = "myDelayedExchange";
    public static final String QUEUE_NAME = "delayed.queue";
    public static final String ROUTING_KEY = "delayed.routing.key";

    @Bean
    public CustomExchange delayedExchange(){
        return new CustomExchange(EXCHANGE_NAME,
                "x-delayed-message", // 消息类型
                true, // 是否持久化
                false); // 是否自动删除
    }

    @Bean
    public Queue delayedQueue(){
        return QueueBuilder.durable(QUEUE_NAME)
                .withArgument("x-delayed-type", "direct")
                .build();
    }

    @Bean
    public Binding delayedBinding(Queue delayedQueue,CustomExchange delayedExchange){
        return BindingBuilder.bind(delayedQueue()).to(delayedExchange()).with(ROUTING_KEY).noargs();
    }
}
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import org.springframework.amqp.rabbit.core.RabbitTemplate;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
public class DelayedMessageProducer {

    @Autowired
    private RabbitTemplate rabbitTemplate;

    @Scheduled(fixedDelay = 5000)
    public void sendDelayedMessage(String message){
        rabbitTemplate.convertAndSend(DelayedExchangeConfig.EXCHANGE_NAME,
                DelayedExchangeConfig.ROUTING_KEY,
                message,
                messagePostProcessor -> {
                    messagePostProcessor.getMessageProperties().setDelay(10000); // 设置延迟时间，单位毫秒
                    return messagePostProcessor;
                });
    }
}
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import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/delayed")
public class DelayedMessageController {
    @Autowired
    private DelayedMessageProducer delayedMessageProducer;

    @GetMapping("/send")
    public String sendDirectMessage(@RequestParam String message){
        delayedMessageProducer.sendDelayedMessage(message);
        return "Delayed message sent to Exchange: " + message;
    }
}
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import org.springframework.amqp.rabbit.annotation.RabbitListener;
import org.springframework.stereotype.Component;


@Component
public class DelayedMessageConsumer {

    @RabbitListener(queues = DelayedExchangeConfig.QUEUE_NAME)
    public void receiveDelayedMessage(String message){
        System.out.println("Received delayed message: " + message);
    }
}
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