public abstract class TransactionSynchronizationManager {
	private static final Log logger = LogFactory.getLog(TransactionSynchronizationManager.class);
	private static final ThreadLocal<Map<Object, Object>> resources =
			new NamedThreadLocal<>("Transactional resources");
	private static final ThreadLocal<Set<TransactionSynchronization>> synchronizations =
			new NamedThreadLocal<>("Transaction synchronizations");
	private static final ThreadLocal<String> currentTransactionName =
			new NamedThreadLocal<>("Current transaction name");
	private static final ThreadLocal<Boolean> currentTransactionReadOnly =
			new NamedThreadLocal<>("Current transaction read-only status");
	private static final ThreadLocal<Integer> currentTransactionIsolationLevel =
			new NamedThreadLocal<>("Current transaction isolation level");
	private static final ThreadLocal<Boolean> actualTransactionActive =
			new NamedThreadLocal<>("Actual transaction active");
    // ...
}

    public void save(){
        // 保存用戶
        saveUser();
        // 發(fā)送消息 異步執(zhí)行
        executorService.execute(() -> sendMessage());
    }

    public void save(){
        // 保存用戶
        saveUser();
        // 判斷當(dāng)前線程是否存在活躍狀態(tài)的事務(wù)
        boolean actualTransactionActive = TransactionSynchronizationManager.isActualTransactionActive();
        // 不存在則事務(wù)都完成
        if (!actualTransactionActive){
            // 異步操作 發(fā)送消息
            executorService.execute(() -> sendMessage());
        }else{
            // 存在活躍事務(wù), 則監(jiān)聽事務(wù), afterCommit是指事務(wù)提交完再執(zhí)行
            TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronizationAdapter() {
                @Override
                public void afterCommit() {
                   // 異步操作 發(fā)送消息
                    executorService.execute(() -> sendMessage());
                }
            });
        }
}

public abstract class TransactionSynchronizationAdapter implements TransactionSynchronization, Ordered {
	@Override
	public int getOrder() {
		return Ordered.LOWEST_PRECEDENCE;
	}
    // 暫停此同步 應(yīng)該從事務(wù)同步管理器中解綁資源
	@Override
	public void suspend() {
	}
    //  恢復(fù)此同步。 應(yīng)該將資源重新綁定到 TransactionSynchronizationManager
	@Override
	public void resume() {
	}
    // 將基礎(chǔ)會話刷新到數(shù)據(jù)存儲
	@Override
	public void flush() {
	}
    // 在事務(wù)提交之前調(diào)用（在完成之前之前）順序倒數(shù)第四
	@Override
	public void beforeCommit(boolean readOnly) {
	}
    // 在事務(wù)提交/回滾之前調(diào)用。順序倒數(shù)第三
	@Override
	public void beforeCompletion() {
	}
    // 在事務(wù)提交后調(diào)用  順序倒數(shù)第二
	@Override
	public void afterCommit() {
	}
    // 在事務(wù)提交/回滾后調(diào)用 可以進(jìn)行資源清理 順序倒數(shù)第一
	@Override
	public void afterCompletion(int status) {
	}
}