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？

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() {
                    @Override
                    public 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];
    }