• thread: Session 对象的生命周期与本地线程绑定
• jta*: Session 对象的生命周期与 JTA 事务绑定
• managed: Hibernate 托付程序来管理 Session 对象的生命周期
  
  
  

• 当一个线程(threadA)第一次调用 SessionFactory 对象的 getCurrentSession() 方法时, 该方法会创建一个新的 Session(sessionA) 对象, 把该对象与 threadA 绑定, 并将 sessionA 返回
  
• 当 threadA 再次调用 SessionFactory 对象的 getCurrentSession() 方法时, 该方法将返回 sessionA 对象
  
• 当 threadA 提交 sessionA 对象关联的事务时, Hibernate 会自己主动flush sessionA 对象的缓存, 然后提交事务, 关闭 sessionA 对象. 当 threadA 撤销 sessionA 对象关联的事务时, 也会自己主动关闭 sessionA 对象
  
• 若 threadA 再次调用 SessionFactory 对象的 getCurrentSession() 方法时, 该方法会又创建一个新的 Session(sessionB) 对象, 把该对象与 threadA 绑定, 并将 sessionB 返回
  
  

package com.atguigu.hibernate.hibernate;

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();
	}

}

package com.atguigu.hibernate.dao;

import org.hibernate.Session;

import com.atguigu.hibernate.entities.Department;
import com.atguigu.hibernate.hibernate.HibernateUtils;

public class DepartmentDao {

	public void save(Department dept){
		//内部获取 Session 对象
		//获取和当前线程绑定的 Session 对象
		//1. 不须要从外部传入 Session 对象
		//2. 多个 DAO 方法也能够使用一个事务!
		Session session = HibernateUtils.getInstance().getSession();
		System.out.println(session.hashCode());
		
		session.save(dept);
	}
	
	/**
	 * 若须要传入一个 Session 对象, 则意味着上一层(Service)须要获取到 Session 对象.
	 * 这说明上一层须要和 Hibernate 的 API 紧密耦合. 所以不推荐使用此种方式. 
	 */
	public void save(Session session, Department dept){
		session.save(dept);
	}
	
}

package com.atguigu.hibernate.test;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.List;

import org.hibernate.Criteria;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.hibernate.criterion.Conjunction;
import org.hibernate.criterion.Disjunction;
import org.hibernate.criterion.MatchMode;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projections;
import org.hibernate.criterion.Restrictions;
import org.hibernate.jdbc.Work;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import com.atguigu.hibernate.dao.DepartmentDao;
import com.atguigu.hibernate.entities.Department;
import com.atguigu.hibernate.entities.Employee;
import com.atguigu.hibernate.hibernate.HibernateUtils;

public class HibernateTest {

	private SessionFactory sessionFactory;
	private Session session;
	private Transaction transaction;
	
	@Before
	public void init(){
		Configuration configuration = new Configuration().configure();
		ServiceRegistry serviceRegistry = 
				new ServiceRegistryBuilder().applySettings(configuration.getProperties())
				                            .buildServiceRegistry();
		sessionFactory = configuration.buildSessionFactory(serviceRegistry);
		
		session = sessionFactory.openSession();
		transaction = session.beginTransaction();
	}
	
	@After
	public void destroy(){
		transaction.commit();
		session.close();
		sessionFactory.close();
	}
	

	
	@Test
	public void testManageSession(){
		
		//获取 Session
		//开启事务
		Session session = HibernateUtils.getInstance().getSession();
		System.out.println("-->" + session.hashCode());
		Transaction transaction = session.beginTransaction();
		
		DepartmentDao departmentDao = new DepartmentDao();
		
		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()); 
	}

}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
		"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
    
    	<!-- Hibernate 连接数据库的基本信息 -->
    	<property name="connection.username">scott</property>
    	<property name="connection.password">java</property>
    	<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
    	<property name="connection.url">jdbc:oracle:thin:@localhost:1521:orcl</property>

		<!-- Hibernate 的基本配置 -->
		<!-- Hibernate 使用的数据库方言 -->
		<property name="dialect">org.hibernate.dialect.Oracle10gDialect</property>
	
		<!-- 执行时是否打印 SQL -->
    	<property name="show_sql">true</property>
    
    	<!-- 执行时是否格式化 SQL -->
    	<property name="format_sql">true</property>
    
    	<!-- 生成数据表的策略 -->
    	<property name="hbm2ddl.auto">update</property>
    	
    	<!-- 设置 Hibernate 的事务隔离级别 -->
    	<property name="connection.isolation">2</property>
    	
    	<!-- 删除对象后, 使其 OID 置为 null -->
    	<property name="use_identifier_rollback">true</property>
    	
    	<!-- 配置 C3P0 数据源 -->
    	<!--  
    	<property name="hibernate.c3p0.max_size">10</property>
    	<property name="hibernate.c3p0.min_size">5</property>
    	<property name="c3p0.acquire_increment">2</property>
    	
    	<property name="c3p0.idle_test_period">2000</property>
    	<property name="c3p0.timeout">2000</property>
    	
    	<property name="c3p0.max_statements">10</property>
    	-->
    	
    	<!-- 设定 JDBC 的 Statement 读取数据的时候每次从数据库中取出的记录条数 -->
    	<property name="hibernate.jdbc.fetch_size">100</property>
    	
    	<!-- 设定对数据库进行批量删除，批量更新和批量插入的时候的批次大小 -->
    	<property name="jdbc.batch_size">30</property>
    	
    	<!-- 启用二级缓存 -->
		<property name="cache.use_second_level_cache">true</property>
    	
    	<!-- 配置使用的二级缓存的产品 -->
    	<property name="hibernate.cache.region.factory_class">org.hibernate.cache.ehcache.EhCacheRegionFactory</property>
    	
    	<!-- 配置启用查询缓存 -->
    	<property name="cache.use_query_cache">true</property>
    	
    	<!-- 配置管理 Session 的方式 -->
    	<property name="current_session_context_class">thread</property>
    	
    	<!-- 须要关联的 hibernate 映射文件 .hbm.xml -->
		<mapping resource="com/atguigu/hibernate/entities/Department.hbm.xml"/>
		<mapping resource="com/atguigu/hibernate/entities/Employee.hbm.xml"/>
		
		<class-cache usage="read-write" class="com.atguigu.hibernate.entities.Employee"/>
		<class-cache usage="read-write" class="com.atguigu.hibernate.entities.Department"/>
		<collection-cache usage="read-write" collection="com.atguigu.hibernate.entities.Department.emps"/>
    </session-factory>
</hibernate-configuration>