RabbitMQ学习笔记：Springboot amqp之 spring_listener_return_correlation、 spring_returned_message_correlati

叁歲伎倆 2023-06-25 10:17 27阅读 0赞

##### 1.引入springboot amqp依赖 #####

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-amqp</artifactId>
            </dependency>

启用消息未成功发送到队列时强制退回及开启回调功能：

spring.rabbitmq.publisher-returns=true
    spring.rabbitmq.template.mandatory=true

##### 2.发送消息到RabbitMQ消息服务器我们可以看到headers有两个属性 #####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9taW5neWFuZy5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70]

这两个属性分别代表什么意思呢？我们看下org.springframework.amqp.rabbit.connection.PublisherCallbackChannel接口：

public interface PublisherCallbackChannel extends Channel { 
    
    	/** * Header used to determine which listener to invoke for a returned message. */
    	String RETURN_LISTENER_CORRELATION_KEY = "spring_listener_return_correlation";
    
    	/** * Header used to locate a pending confirm to which to attach a returned message. */
    	String RETURNED_MESSAGE_CORRELATION_KEY = "spring_returned_message_correlation";
    	}

*  spring\_listener\_return\_correlation:该属性是用来确定消息被退回时调用哪个监听器
 *  spring\_returned\_message\_correlation：该属性是指退回待确认消息的唯一标识

##### 3.spring\_returned\_message\_correlation在哪里设置，又有什么作用？ #####

> 发送消息时有一个退回消息相关数据org.springframework.amqp.rabbit.connection.CorrelationData类，这个header属性对应相关数据类的Id属性

private final RabbitTemplate.ReturnCallback returnCallback = new RabbitTemplate.ReturnCallback() { 
            @Override
            public void returnedMessage(Message message, int replyCode, String replyText, String exchange, String routingKey) { 
                System.err.println("return exchange: " + exchange + ", routingKey: "
                        + routingKey + ", replyCode: " + replyCode + ", replyText: " + replyText+",MessageId:"+message.getMessageProperties().getMessageId());
            }
        };
    
    
    public void sendMsg(String exchange, String routingKey, String message, Map<String, Object> properties){ 
            org.springframework.messaging.Message msg = org.springframework.messaging.support.MessageBuilder.withPayload(message).build();
            /** * 设置生产者消息publish-confirm回调函数 */
            this.rabbitTemplate.setConfirmCallback(confirmCallback);
            /** * 设置消息退回回调函数 */
            this.rabbitTemplate.setReturnCallback(returnCallback);
            /** * 将消息主题和属性封装在Message类中 */
            Message returnedMessage = MessageBuilder.withBody(message.getBytes()).build();
            /** * 相关数据 */
            CorrelationData correlationData = new CorrelationData();
            /** * 消息ID，全局唯一 */
            correlationData.setId(msg.getHeaders().getId().toString());
    
            /** * 设置此相关数据的返回消息 */
            correlationData.setReturnedMessage(returnedMessage);
            /** * 如果msg是org.springframework.amqp.core.Message对象的实例，则直接返回，否则转化为Message对象 */
            this.rabbitTemplate.convertAndSend(exchange, routingKey, msg, new MessagePostProcessor() { 
                /** * 消息后置处理器，消息在转换成Message对象之后调用，可以用来修改消息中的属性、header */
                @Override
                public Message postProcessMessage(Message message) throws AmqpException { 
    				...
                    return message;
                }
            }, correlationData);
        }

对应上面代码的correlationData.setId(msg.getHeaders().getId().toString());方法

> 这个消息ID主要是用来在发送端记录发送了哪些消息，哪些消息已经成功确认，哪些消息发送失败，需要进一步的处理，如重试等等；

##### 4.spring\_listener\_return\_correlation属性是在哪里设置的？又是起什么作用？ #####

在org.springframework.amqp.rabbit.core.RabbitTemplate类中有如下方法：

//随机生成
    private final String uuid = UUID.randomUUID().toString();
    
    public void doSend(Channel channel, String exchangeArg, String routingKeyArg, Message message, // NOSONAR complexity
    			boolean mandatory, @Nullable CorrelationData correlationData)
    					throws Exception {  // NOSONAR TODO: change to IOException in 2.2.
    
    		...
    
    		Message messageToUse = message;
    		MessageProperties messageProperties = messageToUse.getMessageProperties();
    		if (mandatory) { 
    //设置spring_listener_return_correlation属性值 
                messageProperties.getHeaders().put(PublisherCallbackChannel.RETURN_LISTENER_CORRELATION_KEY, this.uuid);
    		}
    		if (this.beforePublishPostProcessors != null) { 
    			for (MessagePostProcessor processor : this.beforePublishPostProcessors) { 
    				messageToUse = processor.postProcessMessage(messageToUse, correlationData);
    			}
    		}
        //在此方法中会从退回消息相关数据类中取spring_returned_message_correlation设置到Message对象
    		setupConfirm(channel, messageToUse, correlationData);
    		if (this.userIdExpression != null && messageProperties.getUserId() == null) { 
    			String userId = this.userIdExpression.getValue(this.evaluationContext, messageToUse, String.class);
    			if (userId != null) { 
    				messageProperties.setUserId(userId);
    			}
    		}
    		sendToRabbit(channel, exch, rKey, mandatory, messageToUse);
    		// Check if commit needed
    		if (isChannelLocallyTransacted(channel)) { 
    			// Transacted channel created by this template -> commit.
    			RabbitUtils.commitIfNecessary(channel);
    		}
    	}

spring\_returned\_message\_correlation属性设置

private void setupConfirm(Channel channel, Message message, @Nullable CorrelationData correlationDataArg) { 
    		if ((this.publisherConfirms || this.confirmCallback != null) && channel instanceof PublisherCallbackChannel) { 
    
    			PublisherCallbackChannel publisherCallbackChannel = (PublisherCallbackChannel) channel;
    			CorrelationData correlationData = this.correlationDataPostProcessor != null
    					? this.correlationDataPostProcessor.postProcess(message, correlationDataArg)
    					: correlationDataArg;
    			long nextPublishSeqNo = channel.getNextPublishSeqNo();
    			message.getMessageProperties().setPublishSequenceNumber(nextPublishSeqNo);
    			publisherCallbackChannel.addPendingConfirm(this, nextPublishSeqNo,
    					new PendingConfirm(correlationData, System.currentTimeMillis()));
    			if (correlationData != null && StringUtils.hasText(correlationData.getId())) { 
    				message.getMessageProperties().setHeader(PublisherCallbackChannel.RETURNED_MESSAGE_CORRELATION_KEY,
    						correlationData.getId());
    			}
    		}
    		else if (channel instanceof ChannelProxy && ((ChannelProxy) channel).isConfirmSelected()) { 
    			long nextPublishSeqNo = channel.getNextPublishSeqNo();
    			message.getMessageProperties().setPublishSequenceNumber(nextPublishSeqNo);
    		}
    	}

> spring\_listener\_return\_correlation的属性作用是确认调用哪个监听器，即消息退回处理回调方法。

GitHub地址：[https://github.com/mingyang66/spring-parent/tree/master/spring-boot-control-rabbitmq-service][https_github.com_mingyang66_spring-parent_tree_master_spring-boot-control-rabbitmq-service]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9taW5neWFuZy5ibG9nLmNzZG4ubmV0_size_16_color_FFFFFF_t_70]: https://img-blog.csdnimg.cn/20191226174600463.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9taW5neWFuZy5ibG9nLmNzZG4ubmV0,size_16,color_FFFFFF,t_70
[https_github.com_mingyang66_spring-parent_tree_master_spring-boot-control-rabbitmq-service]: https://github.com/mingyang66/spring-parent/tree/master/spring-boot-control-rabbitmq-service