工具类源码

package com.baizhi.util;
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
/**
 *本工具类有五个方法
 * 1.打开资源      openSession方法
 * 2.释放资源  也就是关闭资源
 * 3.返回dao实现类对象
 * 4.提交事务
 * 5.事务回滚
 * 
 * 
 * 工具类获取Sqlsession的步骤
 * 
 * 
 * 读取配置文件  在mybatis-config.xml中
 * 创建SqlsessionFactory
 * 创建Sqlsession
 * 获取dao实现类对象（这两步骤在测试类中实现）或者在service中获取
 * 测试方发
 * 
 */

public class MybatisUtil  {
	private static SqlSessionFactory factory = null;
	static{
		InputStream in = null;
		try {
			in = Resources.getResourceAsStream("mybatis-config.xml");
			factory = new SqlSessionFactoryBuilder().build(in);
		} catch (Exception e) {
			e.printStackTrace();
			throw new RuntimeException("初始化工厂失败！~");
		}finally{
			try {in.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}
	private static ThreadLocal<SqlSession> tl =  new ThreadLocal<SqlSession>();
	public static SqlSession openSession(){
		SqlSession sqlSession = tl.get();
		if(sqlSession==null){
			sqlSession = factory.openSession();
			tl.set(sqlSession);
		}
		return sqlSession;
	}
	public static void  close(){
		SqlSession sqlSession = openSession();
		sqlSession.close();
		tl.remove();
	}
	public static <T> T getMapper(Class<T> c) {
		SqlSession sqlSession = openSession();
		T t = sqlSession.getMapper(c);
		return t;
	}
	public static void commit(){
		openSession().commit();
	}
	public static void rollback(){
		openSession().rollback();
	}	
}

service调用

package com.baizhi.service;

import java.util.ArrayList;
import java.util.List;
import com.baizhi.dao.UserDAO;
import com.baizhi.entity.User;
import com.baizhi.util.*;

public class UserServiceImpl implements UserService {

    @Override
    public List<User> queryAll() {
        List<User> users = new ArrayList<User>();
        try{
            UserDAO userDAO = MybatisUtil.getMapper(UserDAO.class);
            users = userDAO.selectAll();
            return users;
        } catch(Exception e) {
            e.printStackTrace();
            return null;
        }finally{
            MybatisUtil.close();
        }
    }
}