JPA EntityManager获得session、connection

1、获得Hibernate Session

Session session = entityManager.unwrap(org.hibernate.Session.class);

2、获得java.sql.Connection

方法1：

JPA 2.0
entityManager.getTransaction().begin();
java.sql.Connection connection = entityManager.unwrap(java.sql.Connection.class);
...
entityManager.getTransaction().commit();

但是对于Hibernate3.6.5会报错PersistenceException包含如下信息：Hibernate cannot unwrap interface java.sql.Connection

方法2：

SessionImplementor session =entityManager.unwrap(SessionImplementor.class);
session.connection();

方法3：

Session session = (org.hibernate.Session) em.getDelegate();
SessionFactoryImplementor sf = (SessionFactoryImplementor) session.getSessionFactory();
connection  = sf.getConnectionProvider().getConnection();

hibenate 4.3 :

Session session = (Session) em.getDelegate();
SessionFactoryImpl sessionFactory = (SessionFactoryImpl) session.getSessionFactory();
connection = sessionFactory.getConnectionProvider().getConnection();