@transactional注解与 getCurrentSession

最新推荐文章于 2021-08-09 11:51:06 发布

原创最新推荐文章于 2021-08-09 11:51:06 发布 · 941 阅读

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本文探讨了如何在service层正确应用@transactional注解以实现有效的事务管理。文章强调了使用getCurrentSession而非openSession的重要性，并解释了在不同情况下如何避免常见的错误。

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@transactional注解应添加在service层

使用声明式事务管理@transactional注解式,需要使用getCurrentSession来开启session,

而使用 openSession() 事物不会提交

另外,getCurrentSession是和事物相关的,如果不开启事务,单纯的使用它,
也会报错:Could not obtain transaction-synchronized Session for current thread

@Service("stuServiceImpl")
@Transactional(propagation = Propagation.REQUIRED, readOnly = false)
public class StuServiceImpl implements StuService {
        @Autowired(required=false)

	private StuDaoImpl stuDaoImpl;

}

public void saveAll(Student s, Score ss) {
		System.out.println(" enter StudaoImpl.addAll");
		// 在使用事物声明式事务管理(即:@Transactional),应使用getCurrentSession,
		// 而不能使用openSession,否则事物不会提交
		//另外,getCurrentSession是和事物相关的,如果不开启事务,单纯的使用它,
		//也会报错:Could not obtain transaction-synchronized Session for current thread
		// Session session = sessionFactory.openSession();
		Session session = sessionFactory.getCurrentSession();
		session.save(s);
		session.save(ss);
	}

附:getCurrentSession源码

/**
	 * Retrieve the Spring-managed Session for the current thread, if any.
	 */
	@Override
	public Session currentSession() throws HibernateException {
		Object value = TransactionSynchronizationManager.getResource(this.sessionFactory);
		if (value instanceof Session) {
			return (Session) value;
		}
		else if (value instanceof SessionHolder) {
			SessionHolder sessionHolder = (SessionHolder) value;
			Session session = sessionHolder.getSession();
			if (!sessionHolder.isSynchronizedWithTransaction() &&
					TransactionSynchronizationManager.isSynchronizationActive()) {
				TransactionSynchronizationManager.registerSynchronization(
						new SpringSessionSynchronization(sessionHolder, this.sessionFactory, false));
				sessionHolder.setSynchronizedWithTransaction(true);
				// Switch to FlushMode.AUTO, as we have to assume a thread-bound Session
				// with FlushMode.MANUAL, which needs to allow flushing within the transaction.
				FlushMode flushMode = session.getFlushMode();
				if (flushMode.equals(FlushMode.MANUAL) &&
						!TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
					session.setFlushMode(FlushMode.AUTO);
					sessionHolder.setPreviousFlushMode(flushMode);
				}
			}
			return session;
		}

		if (this.transactionManager != null) {
			try {
				if (this.transactionManager.getStatus() == Status.STATUS_ACTIVE) {
					Session session = this.jtaSessionContext.currentSession();
					if (TransactionSynchronizationManager.isSynchronizationActive()) {
						TransactionSynchronizationManager.registerSynchronization(new SpringFlushSynchronization(session));
					}
					return session;
				}
			}
			catch (SystemException ex) {
				throw new HibernateException("JTA TransactionManager found but status check failed", ex);
			}
		}

		if (TransactionSynchronizationManager.isSynchronizationActive()) {
			Session session = this.sessionFactory.openSession();
			if (TransactionSynchronizationManager.isCurrentTransactionReadOnly()) {
				session.setFlushMode(FlushMode.MANUAL);
			}
			SessionHolder sessionHolder = new SessionHolder(session);
			TransactionSynchronizationManager.registerSynchronization(
					new SpringSessionSynchronization(sessionHolder, this.sessionFactory, true));
			TransactionSynchronizationManager.bindResource(this.sessionFactory, sessionHolder);
			sessionHolder.setSynchronizedWithTransaction(true);
			return session;
		}
		else {
			throw new HibernateException("Could not obtain transaction-synchronized Session for current thread");
		}
	}