执行流程
1. 发送方向 MQ 服务端发送消息。
2. MQ Server 将消息持久化成功之后，向发送方 ACK 确认消息已经发送成功，此时消息为半消息。
3. 发送方开始执行本地事务逻辑。
4. 发送方根据本地事务执行结果向 MQ Server 提交二次确认（Commit 或是 Rollback），MQ Server 收到Commit 状态则将半消息标记为可投递，订阅方最终将收到该消息；MQ Server 收到 Rollback 状态则删除半消息，订阅方将不会接受该消息。
5. 在断网或者是应用重启的特殊情况下，上述步骤4提交的二次确认最终未到达 MQ Server，经过固定时间后MQ Server 将对该消息发起消息回查。
6. 发送方收到消息回查后，需要检查对应消息的本地事务执行的最终结果。
7. 发送方根据检查得到的本地事务的最终状态再次提交二次确认，MQ Server 仍按照步骤4对半消息进行操作。
package cn.learn.rocketmq.transaction;import org.apache.rocketmq.client.producer.TransactionMQProducer;import org.mon.message.Message;public class TransactionProducer {public static void main(String[] args) throws Exception {TransactionMQProducer producer = newTransactionMQProducer("transaction_producer");producer.setNamesrvAddr("localhost:9876");// 设置事务监听器producer.setTransactionListener(new TransactionListenerImpl());producer.start();// 发送消息Message message = new Message("pay_topic", "用户A给用户B转账500元".getBytes("UTF-8"));producer.sendMessageInTransaction(message, null);Thread.sleep(999999);producer.shutdown();}}
package cn.learn.rocketmq.transaction;import org.apache.rocketmq.client.producer.LocalTransactionState;import org.apache.rocketmq.client.producer.TransactionListener;import org.mon.message.Message;import org.mon.message.MessageExt;import java.util.HashMap;import java.util.Map;public class TransactionListenerImpl implements TransactionListener {private static Map<String, LocalTransactionState> STATE_MAP = new HashMap<>();/*** 执行具体的业务逻辑** @param msg 发送的消息对象* @param arg* @return*/@Overridepublic LocalTransactionState executeLocalTransaction(Message msg, Object arg) {try {System.out.println("用户A账户减500元.");Thread.sleep(500); //模拟调用服务// System.out.println(1/0);System.out.println("用户B账户加500元.");Thread.sleep(800);STATE_MAP.put(msg.getTransactionId(), MIT_MESSAGE);// 二次提交确认// return LocalTransactionState.UNKNOW;return MIT_MESSAGE;} catch (Exception e) {e.printStackTrace();}STATE_MAP.put(msg.getTransactionId(), LocalTransactionState.ROLLBACK_MESSAGE);// 回滚return LocalTransactionState.ROLLBACK_MESSAGE;}/*** 消息回查** @param msg* @return*/@Overridepublic LocalTransactionState checkLocalTransaction(MessageExt msg) {System.out.println("状态回查 ---> " + msg.getTransactionId() +" " +STATE_MAP.get(msg.getTransactionId()) );return STATE_MAP.get(msg.getTransactionId());}}
package cn.learn.rocketmq.transaction;import org.apache.rocketmq.client.consumer.DefaultMQPushConsumer;import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyContext;import org.apache.rocketmq.client.consumer.listener.ConsumeConcurrentlyStatus;import org.apache.rocketmq.client.consumer.listener.MessageListenerConcurrently;import org.mon.message.MessageExt;import java.io.UnsupportedEncodingException;import java.util.List;public class TransactionConsumer {public static void main(String[] args) throws Exception {DefaultMQPushConsumer consumer = newDefaultMQPushConsumer("LEARN_CONSUMER");consumer.setNamesrvAddr("localhost:9876");// 订阅topic，接收此Topic下的所有消息consumer.subscribe("pay_topic", "*");consumer.registerMessageListener(new MessageListenerConcurrently() {@Overridepublic ConsumeConcurrentlyStatus consumeMessage(List<MessageExt> msgs,ConsumeConcurrentlyContext context) {for (MessageExt msg : msgs) {try {System.out.println(new String(msg.getBody(), "UTF-8"));} catch (UnsupportedEncodingException e) {e.printStackTrace();}}return ConsumeConcurrentlyStatus.CONSUME_SUCCESS;}});consumer.start();}}
