以下对我有用:
数据源配置.java
@Bean
public LocalSessionFactoryBean sessionFactory() {
// Link your data source to your session factory
...
}
@Bean("hibernateTxManager")
public HibernateTransactionManager hibernateTxManager(@Qualifier("sessionFactory") SessionFactory sessionFactory) {
// Link your session factory to your transaction manager
...
}
MyServiceImpl.java
@Service
@Transactional(propagation = Propagation.REQUIRES_NEW, transactionManager = "hibernateTxManager", readOnly = true)
public class MyServiceImpl implements MyService {
@Autowired
private MyRepo myRepo;
...
Stream<MyEntity> stream = myRepo.getStream();
// Do your streaming and CLOSE the steam afterwards
...
MyRepoImpl.java
@Repository
@Transactional(propagation = Propagation.MANDATORY, transactionManager = "hibernateTxManager", readOnly = true)
public class MyRepoImpl implements MyRepo {
@Autowired
private SessionFactory sessionFactory;
@Autowired
private MyDataSource myDataSource;
public Stream<MyEntity> getStream() {
return sessionFactory.openStatelessSession(DataSourceUtils.getConnection(myDataSource))
.createNativeQuery("my_query", MyEntity.class)
.setReadOnly(true)
.setFetchSize(1000)
.stream();
}
...
请记住,当您进行流式传输时,您实际上只需要在对象物化时注意内存。这确实是该操作中唯一容易受到内存问题影响的部分。就我而言,我一次将流分块为 1000 个对象,使用 gson 将它们序列化并立即将它们发送到 JMS 代理。垃圾收集器完成其余的工作。
值得注意的是,Spring 的事务边界感知在最后关闭了与 dB 的连接,无需明确告知。