问题描述

在一个事务内完成插入操作，通过MQ异步通知其他微服务进行事件处理。
由于是在事务内发送，其他服务消费消息，查询数据时还不存在如何解决呢？

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解决方案

通过spring-tx包的TransactionSynchronizationManager事务管理器解决。

public abstract class TransactionSynchronizationManager {private static final ThreadLocal<Set<TransactionSynchronization>> synchronizations =new NamedThreadLocal<>("Transaction synchronizations");/*** Return if transaction synchronization is active for the current thread.* Can be called before register to avoid unnecessary instance creation.* @see #registerSynchronization*/		public static boolean isSynchronizationActive() {return (synchronizations.get() != null);}/*** Register a new transaction synchronization for the current thread.* Typically called by resource management code.* <p>Note that synchronizations can implement the* {@link org.springframework.core.Ordered} interface.* They will be executed in an order according to their order value (if any).* @param synchronization the synchronization object to register* @throws IllegalStateException if transaction synchronization is not active* @see org.springframework.core.Ordered*/public static void registerSynchronization(TransactionSynchronization synchronization)throws IllegalStateException {Assert.notNull(synchronization, "TransactionSynchronization must not be null");Set<TransactionSynchronization> synchs = synchronizations.get();if (synchs == null) {throw new IllegalStateException("Transaction synchronization is not active");}synchs.add(synchronization);}}

Rocketmq方法封装，通过TransactionSynchronizationManager.isSynchronizationActive()判断当前方法的调用是否在事务内。
如果是，则注册一个事务同步适配器，在事务提交后发送消息。
否则直接发送。

    /*** 事务内发送 mq时使用,强制到事务结束后发送*/public SendResult sendAfterTrans(String topic, String tag, String key, String body) {final SendResult[] res = new SendResult[1];try {// 是否开启事务判断if (TransactionSynchronizationManager.isSynchronizationActive()) {log.debug("Mysql事务内Mq消息发送  延迟到事务提交后 waiting……");TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {@Overridepublic void afterCommit() {log.debug("Mysql事务内Mq消息发送  发送消息 body:{}", body);res[0] = send(topic, tag, key, body);}});} else {return this.send(topic, tag, key, body);}} catch (Exception e) {e.printStackTrace();}return res[0];}