RocketMQ源码解析：手把手教老婆看懂consumer接收到的MessageExt

比眉伴天荒 2022-11-18 01:15 199阅读 0赞

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[RocketMQ使用教程相关系列 目录][RocketMQ_]

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**目录**

源代码说明

MessageExt的源码解析

继承于Message，Message源码解析

喝点毒鸡汤

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# 源代码说明 #

MessageExt位于此包下：

package org.apache.rocketmq.common.message;

# MessageExt的源码解析 #

参数说明在代码里

public class MessageExt extends Message {
        private static final long serialVersionUID = 5720810158625748049L;
    
        //记录MessageQueue编号，消息在Topic下对应的MessageQueue中被拉取
        private int queueId;
    
        //记录消息在Broker存盘大小
        private int storeSize;
    
        //记录在ConsumeQueue中的偏移
        private long queueOffset;
    
        //记录一些系统标志的开关状态，MessageSysFlag中定义了系统标识
        private int sysFlag;
    
        //消息创建时间，在Producer发送消息时设置
        private long bornTimestamp;
    
        //记录发送该消息的producer地址
        private SocketAddress bornHost;
    
        //消息存储时间
        private long storeTimestamp;
    
        //记录存储该消息的Broker地址
        private SocketAddress storeHost;
    
        //消息Id
        private String msgId;
    
        //记录消息在Broker中存储偏移
        private long commitLogOffset;
    
        //消息内容CRC校验值
        private int bodyCRC;
    
        //消息重试消费次数
        private int reconsumeTimes;
    
        //这个参数没看懂，知道的大佬分享下
        private long preparedTransactionOffset;
    
    //省略get set
    
       
        @Override
        public String toString() {
            return "MessageExt [queueId=" + queueId + ", storeSize=" + storeSize + ", queueOffset=" + queueOffset
                + ", sysFlag=" + sysFlag + ", bornTimestamp=" + bornTimestamp + ", bornHost=" + bornHost
                + ", storeTimestamp=" + storeTimestamp + ", storeHost=" + storeHost + ", msgId=" + msgId
                + ", commitLogOffset=" + commitLogOffset + ", bodyCRC=" + bodyCRC + ", reconsumeTimes="
                + reconsumeTimes + ", preparedTransactionOffset=" + preparedTransactionOffset
                + ", toString()=" + super.toString() + "]";
        }
    }

# 继承于Message，Message源码解析 #

public class Message implements Serializable {
        private static final long serialVersionUID = 8445773977080406428L;
        //主题
        private String topic;
    
        //网络通信层标记
        private int flag;
    
        /**
         *MIN_OFFSET：最小偏移
         * MAX_OFFSET：最大偏移
         * CONSUME_START_TIME：消费拉取时间
         *UNIQ_KEY：
         * CLUSTER：集群
         * WAIT：
         * TAGS：消息标签
         *DELAY：延时级别
         **/
        private Map<String, String> properties;
    
        //Producer发送的实际消息内容，以字节数组（ASCII码）形式进行存储。Message消息有一定大小限制。
        private byte[] body;
    
        //事务消息相关的事务编号
        private String transactionId;
    
       //得到延时级别
        public int getDelayTimeLevel() {
            String t = this.getProperty(MessageConst.PROPERTY_DELAY_TIME_LEVEL);
            if (t != null) {
                return Integer.parseInt(t);
            }
    
            return 0;
        }
    
    //设置延时级别
        public void setDelayTimeLevel(int level) {
            this.putProperty(MessageConst.PROPERTY_DELAY_TIME_LEVEL, String.valueOf(level));
        }
    
    //省略 get set
    
        
        @Override
        public String toString() {
            return "Message{" +
                "topic='" + topic + '\'' +
                ", flag=" + flag +
                ", properties=" + properties +
                ", body=" + Arrays.toString(body) +
                ", transactionId='" + transactionId + '\'' +
                '}';
        }
    }

# 喝点毒鸡汤 #

每天读点源码，进步一小步，成长一大步。

[RocketMQ_]: https://blog.csdn.net/shi_hong_fei_hei/article/details/115470425