管理Session

1：把session和本地线程绑定在一起。

1）：创建一个sessionFactory。然后由它去创建session

package com.hq.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateUtils {
    
    private HibernateUtils(){}
    
    private static HibernateUtils instance=new HibernateUtils();
    
    public static HibernateUtils getInstance(){
        return instance;
    }
    
    private SessionFactory sessionFactory;
    public SessionFactory getSessionFactory() {
        if (sessionFactory == null) {
            Configuration configuration = new Configuration().configure();
            ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
                    .applySettings(configuration.getProperties())
                    .buildServiceRegistry();
            sessionFactory = configuration.buildSessionFactory(serviceRegistry);
        }
        return sessionFactory;
    }
    
    public Session getSession(){
        return getSessionFactory().getCurrentSession();
    }
}

使用：getCurrentSession()方法。

2）：通过单例的HibernateUtils来得到session

public class DeptDao {
    public void save(Department dept){
        Session session=HibernateUtils.getInstance().getSession();
        System.out.println(session.hashCode());
//        session.save(dept);
    }
    
}

3）：在配置文件中配置

<!-- 配置管理session的方法 -->
        <property name="current_session_context_class">thread</property>

4）：测试

@org.junit.Test
    public void testSession(){
                //获取 Session
                //开启事务
                Session session = HibernateUtils.getInstance().getSession();
                System.out.println("-->" + session.hashCode());
                Transaction transaction = session.beginTransaction();
                DeptDao departmentDao = new DeptDao();
                
                Department dept = new Department();
                dept.setName("ATGUIGU");
                
                departmentDao.save(dept);
                departmentDao.save(dept);
                departmentDao.save(dept);
                
                //若 Session 是由 thread 来管理的, 则在提交或回滚事务时, 已经关闭 Session 了. 
                transaction.commit();
                System.out.println(session.isOpen()); 
    }