java - EJB 事务回滚后自动重试

Question

基本上，我有一个 JMS 队列和一个 MDB，用于从 JMS 队列收集消息，对它们进行一些处理，然后通过 JPA 将消息保存到数据库中。我将负责将消息保存到数据库中的方法标记为在新事务中启动:

@TransactionAttribute(TransactionAttributeType.REQUIRES_NEW)
public void create(T entity)
{
    try
    {
        getEntityManager().persist(entity);
    }
    catch(Exception e)
    {
        throw new RuntimeException("DB Exception");
    }
}

如果事务被回滚，它是否会自动退役直到事务完成？如果没有，如何启用它？

Answer 1

如果异常传播到 MDB，事务将不会提交，消息将不会被确认为已接收并将重试。来自 EJB 3.1 规范:

Message acknowledgment is automatically handled by the container. If the message-driven bean uses container-managed transaction demarcation, message acknowledgment is handled automatically as a part of the transaction commit.

我对 Weblogic 不熟悉，但应该有一个 JMS 队列参数，用于设置重试次数、重试间隔等，直到消息被丢弃或放入未传递的队列中。

但通常最好在 MDB 中捕获异常，因为从 MDB 抛出的 RuntimeException 会导致 bean 被容器。来自 EJB 3.1 规范:

Message-driven beans should not, in general, throw RuntimeExceptions.

A RuntimeException that is not an application exception thrown from any method of the message-driven bean class (including a message listener method and the callbacks invoked by the container) results in the transition to the “does not exist” state.

例如，最好有:

public class MyMDB implements MessageListener {

  @Resource
  private MessageDrivenContext context;

  public void onMessage() {
     try {
        //some other processing
        someService.create(entity);
     }
     catch(Exception e) {
        //mark the message as undelivered
        context.setRollbackOnly();
     }
  }
}