Java entitymanager.close() 不关闭与数据库的连接
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/19107408/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
entitymanager.close() not closing connections to database
提问by Sumit Gupta
I'm developing a quiz system and I'm new to JPA & Hibernate. I've used hibernate 4.2.3 and I've used c3p0 connection pooling. Code works fine but each EntityManager creates a connection which is never closed. And once the max number of connections are reached then application can't access database. I'm using MySQL 5.6.10, when I see connections in workbench I never see connections being destroyed. And application is not reusing the connections.
我正在开发一个测验系统，我是 JPA 和 Hibernate 的新手。我使用了 hibernate 4.2.3 并且使用了 c3p0 连接池。代码工作正常，但每个 EntityManager 创建一个永不关闭的连接。一旦达到最大连接数，应用程序将无法访问数据库。我正在使用 MySQL 5.6.10，当我在工作台中看到连接时，我从未看到连接被破坏。并且应用程序没有重用连接。
My guess is that connections are not returned to connection pool. I dunno how as i have written "manager.close()".
我的猜测是连接不会返回到连接池。我不知道如何写“manager.close()”。
The same happens with hibernate internal connection pooling. (In case i remove c3p0.)
休眠内部连接池也会发生同样的情况。（如果我删除了 c3p0。）
Here are the properties of "persistence.xml"
这是“persistence.xml”的属性
<property name="hibernate.connection.provider_class" value="org.hibernate.service.jdbc.connections.internal.C3P0ConnectionProvider" />
<property name="hibernate.c3p0.max_size" value="10" />
<property name="hibernate.c3p0.min_size" value="2" />
<property name="hibernate.c3p0.acquire_increment" value="1" />
<property name="hibernate.c3p0.idle_test_period" value="5000" />
<property name="hibernate.c3p0.max_statements" value="20" />
<property name="hibernate.c3p0.timeout" value="500" />
Here is how i access EntityManagerFactory
这是我访问 EntityManagerFactory 的方式
public class EntityMangFactory {
private static EntityManagerFactory emf=null;
private static void initEntityManagerFactory()
{
emf=Persistence.createEntityManagerFactory("com.oes.jpa"); //persistence-unit-name//
}
public static EntityManagerFactory getEntityManagerFactory()
{
if(emf==null){
initEntityManagerFactory();
}
return emf;
}
}
Here is how i access the database.
这是我访问数据库的方式。
public static List<MarksDTO> getMarks(int id){
EntityManagerFactory factory= EntityMangFactory.getEntityManagerFactory();
EntityManager manager= factory.createEntityManager();
manager.getTransaction().begin();
TypedQuery<MarksDTO> q= manager.createQuery("select new com.examsystem.DTO.MarksDTO(m.courseId,m.score,m.setNo,m.courseName) from MarksBean as m where TraineeID=:TraineeID",MarksDTO.class);
q.setParameter("TraineeID", id);
List<MarksDTO> ls=q.getResultList();
manager.close();
return ls;
}
Please point me to where I'm wrong.
请指出我错的地方。
Thanks in advance.
提前致谢。
回答by Sumit Gupta
I wasn't committing each transaction. Hence the problem.
我没有提交每笔交易。因此问题来了。
