Java/Spring : How to specify order for nested transactions with TransactionSynchronizationManager

Question

我有一些逻辑需要在事务提交后执行，所以我使用如下所示的内容:

TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronization() {
                @Override
                public void afterCommit() {
                    //do work
                }
            });

这工作得很好。我的问题是，如果我在嵌套事务中注册多个像这样的处理程序，顺序是否保证在注册顺序中？例如:

class Obj1 {
   @Transactional
   public void doTX1() {
      //invoke another method that is marked as transactional
      obj2.doInnerTx();

      TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronization() {
                    @Override
                    public void afterCommit() {
                        System.out.println("Outer TX");
                    }
                });
   }
}

 class Obj2 {
       @Transactional
       public void doInnerTx() {
          TransactionSynchronizationManager.registerSynchronization(new TransactionSynchronization() {
                        @Override
                        public void afterCommit() {
                            System.out.println("Inner TX");
                        }
                    });
       }
    }

输出:

Inner TX
Outer TX

但这能保证吗？如果不是，我将如何强制执行顺序，使内部始终首先执行？

Answer 1

registerSynchronization()方法的javadoc说:

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)

如果您使用 new TransactionSynchronizationAdapter() {..} 而不是 new TransactionSynchronization() {..}，则可以重写 getOrder() 方法以及 afterCommit()，因为 TransactionSynchronizationAdapter 已经实现了 Ordered 接口(interface)。来自javadoc:

The default * {@link #getOrder() order} is 
{@link Ordered#LOWEST_PRECEDENCE}, indicating * late execution; return a lower 
value for earlier execution.

最低优先级值为Integer.MAX_VALUE