RabbitMQ学习10死信队列(队列达到最大长度)

队列可以设置最大接受信息的长度，如果等待被消费而排队的消息的数量，大于这个长度，就会转发给死信队列。

1、生产者代码：

package com.yas.deadexchange;

import com.rabbitmq.client.AMQP;
import com.rabbitmq.client.BuiltinExchangeType;
import com.rabbitmq.client.Channel;
import com.yas.config.RabbitMQClient;
import org.junit.Test;

public class Publisher_MaxLength {
    private static final String NORMAL_EXCHANGE = "normal_exchange";

    @Test
    public void publish() throws Exception {
        try (Channel channel = RabbitMQClient.getChannel()) {
            channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
            //设置消息的 TTL 时间
            //AMQP.BasicProperties properties = new AMQP.BasicProperties().builder().expiration("10000").build();
            //该信息是用作演示队列个数限制
            for (int i = 1; i <11 ; i++) {
                String message="info"+i;
                //channel.basicPublish(NORMAL_EXCHANGE, message.getBytes());
                channel.basicPublish(NORMAL_EXCHANGE,"zhangsan",null,message.getBytes());
                System.out.println("生产者发送消息:"+message);
            }
        }
    }
}

2、普通队列消费者代码：

package com.yas.deadexchange;

import com.rabbitmq.client.BuiltinExchangeType;
import com.rabbitmq.client.Channel;
import com.rabbitmq.client.Connection;
import com.rabbitmq.client.DeliverCallback;
import com.yas.config.RabbitMQClient;
import org.junit.Test;

import java.util.HashMap;
import java.util.Map;

public class Consumer_MaxLength {
    public static final String NORMAL_EXCHANGE = "normal_exchange";
    public static final String DEAD_EXCHANGE = "dead_exchange";
    public static final String NORMAL_QUEUE = "normal_queue";
    public static final String DEAD_QUEUE = "dead_queue";

    @Test
    public void consume() throws Exception {
        //1.获取连接对象
        Connection connection = RabbitMQClient.getConnection();
        //2.创建channel
        Channel channel = connection.createChannel();

        //声明死信交换机 类型为 direct
        channel.exchangeDeclare(DEAD_EXCHANGE, BuiltinExchangeType.DIRECT);
        //声明死信队列
        channel.queueDeclare(DEAD_QUEUE, false, false, false, null);
        //死信队列绑定死信交换机与 routingkey
        channel.queueBind(DEAD_QUEUE, DEAD_EXCHANGE, "lisi");


        //声明普通交换机 类型为 direct
        channel.exchangeDeclare(NORMAL_EXCHANGE, BuiltinExchangeType.DIRECT);
        //正常队列绑定死信队列信息
        Map<String, Object> params = new HashMap<>();
        //正常队列设置死信交换机 参数 key 是固定值
        params.put("x-dead-letter-exchange", DEAD_EXCHANGE);
        //正常队列设置死信 routing-key 参数 key 是固定值
        params.put("x-dead-letter-routing-key", "lisi");

        //正常队列设置最大长度
        params.put("x-max-length",6);

        //声明普通队列
        channel.queueDeclare(NORMAL_QUEUE, false, false, false, params);
        //普通队列绑定普通交换机routing-key
        channel.queueBind(NORMAL_QUEUE, NORMAL_EXCHANGE, "zhangsan");
        System.out.println("等待接收消息........... ");

        //消费者回调
        DeliverCallback deliverCallback = (consumerTag, delivery) -> {
            String message = new String(delivery.getBody(), "UTF-8");
            System.out.println("Consumer01 接收到消息"+message);
            };
        channel.basicConsume(NORMAL_QUEUE, true, deliverCallback, consumerTag -> {
        });

        System.in.read();
        //5/释放资源
        channel.close();
        connection.close();
    }
}

3、测试：

启动生产者，但不启动消费者。会发送10个消息。其中6个消息在普通队列中排队，而4个消息会被转发到死信队列中。

使用普通队列的消费者，只能消费调这6条普通队列中的消息。

通过死信队列的消费者，才能消费调私信队列中的消息。