返回Java 8流的Spring存储库方法不会关闭JDBC连接

问题描述：

我有一个Spring data信息库:

@Repository
interface SomeRepository extends CrudRepository<Entity, Long> {
    Stream<Entity> streamBySmth(String userId);
}

我正在某些Spring bean中调用该方法:

I am calling that method in some Spring bean:

@Scheduled(fixedRate = 10000)
private void someMethod(){
    someRepository.streamBySmth("smth").forEach(this::callSomeMethod);
}

我正在使用MySQL数据库.当我在成功的方法调用后运行应用程序时，它将引发异常:

I am using MySQL database. And when I am running application after some successful method invocations it throws an exception:

o.h.engine.jdbc.spi.SqlExceptionHelper   : SQL Error: 0, SQLState: 08001
o.h.engine.jdbc.spi.SqlExceptionHelper   : Could not create connection to database server.
o.s.s.s.TaskUtils$LoggingErrorHandler    : Unexpected error occurred in scheduled task.

org.springframework.dao.DataAccessResourceFailureException: Unable to acquire JDBC Connection; nested exception is org.hibernate.exception.JDBCConnectionException: Unable to acquire JDBC Connection

看来，Spring没有正确关闭连接.如果我将方法的返回值从Stream更改为List，则它可以正常工作.

It seems, that connection was not closed properly by Spring. If I have changed method return value to List from Stream it works correctly.

更新: Spring Boot版本是1.4.1.RELEASE

UPDATE: Spring Boot version is 1.4.1.RELEASE

答

作为

As the reference documentation clearly states, Streams need to be used with a try-with-resources block.

此外，通过用@Transactional注释周围的方法，确保在消耗流时保持(只读)事务处于打开状态.否则，将应用默认设置，并尝试在返回存储库方法时释放资源.

Also, make sure you keep a (read-only) transaction open for the time of the consumption of the stream by annotating the surrounding method with @Transactional. Otherwise the default settings apply and the resources are attempted to be freed on repository method return.

@Transactional
public void someMethod() {

  try (Stream<User> stream = repository.findAllByCustomQueryAndStream()) {
    stream.forEach(…);
  } 
}

返回Java 8流的Spring存储库方法不会关闭JDBC连接

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