【Mybatis】Mybatis简单使用

一个Mybatis的项目，需要负责连接管理的工具类，每次只需要从工具类获取SqlSessionFactory

package com.hj.utils;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

import java.io.IOException;
import java.io.InputStream;

public class SqlSessionFactoryUtils {
    private static String RESOURCE = "mybatis.xml";
    private static SqlSessionFactory sqlSessionFactory;
    private static ThreadLocal<SqlSession> threadLocal = new ThreadLocal<SqlSession>();

    /**
     * 初始化SqlSession的方法 在容器初始化的时候应加载
     *
     * 使用示例（使用注解方式添加监听器）：
     * import com.damu.utils.SqlSessionFactoryUtils;
     * import javax.servlet.ServletContextEvent;
     * import javax.servlet.ServletContextListener;
     * import javax.servlet.annotation.WebListener;
     * @WebListener
     * public class InitSqlSessionListener implements ServletContextListener {
     *     public void contextInitialized(ServletContextEvent servletContextEvent) {
     *         System.out.println("容器加载中...");
     *         // 初始化我们的SqlSesionFactory对象
     *         SqlSessionFactoryUtils.initSqlSessionFactry();
     *     }
     *
     *     public void contextDestroyed(ServletContextEvent servletContextEvent) {
     *         System.out.println("容器销毁中...");
     *         // 关闭SqlSession对象
     *         SqlSessionFactoryUtils.close();
     *     }
     * }
     */
    public static void initSqlSessionFactory(){
        try {
            InputStream is = Resources.getResourceAsStream(RESOURCE);

            sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取SqlSessionFactory的方法
     * @return
     */
    public static SqlSessionFactory getSqlSessionFactory(){
        return sqlSessionFactory;
    }

    /**
     * 关闭Session的方法
     */
    public static void close(){
        SqlSession session = threadLocal.get();
        if (session != null) {
            session.close();
            threadLocal.set(null);

        }
    }

}

每次服务器启动时候，也可以直接放在DAO中

package com.damu.listener;

import com.damu.utils.SqlSessionFactoryUtils;

import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;


@WebListener
public class InitSqlSessionListener implements ServletContextListener {
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        System.out.println("容器加载中...");
        // 初始化我们的SqlSesionFactory对象
        SqlSessionFactoryUtils.initSqlSessionFactry();
    }

    public void contextDestroyed(ServletContextEvent servletContextEvent) {
        System.out.println("容器销毁中...");
        // 关闭SqlSession对象
        SqlSessionFactoryUtils.close();
    }
}

UserDao中的使用：

import com.damu.entity.Users;
import com.damu.utils.SqlSessionFactoryUtils;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;

import java.util.List;


public class UsersDAO {
    private SqlSession sqlSession;
    private List<Users> list;
    private Users user;

    private SqlSession getSession() {
        sqlSession = SqlSessionFactoryUtils.getSqlSessionFactory().openSession();
        return sqlSession;
    }

    /**
     * 查询全部用户
     * @return
     */
    public List<Users> findAll() {
        try {
            list = getSession().selectList("findUsers");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return list;
    }
}

<select id="findUsers" resultType="com.beans.User">
    select * from users
</select>

 更多操作：

    /**
     * 查询全部用户
     * @return
     */
    public List<Users> findAll(){
        try {
            usersList = getSqlSession().selectList("findUsers");
//            for (Users user :
//                    usersList) {
//                System.out.println(user);
//            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return usersList;
    }

    /**
     * 查询单个用户
     * @return
     */
    public Users findById(Integer id){
        try {
            user = getSqlSession().selectOne("findUsers", new Users(id));
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return user;
    }

    /**
     * 增加用户数据到数据库
     * @return
     */

    public Users addUser(Users user){
        try {
            getSqlSession().insert("addUser", user);
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return user;
    }

    /**
     * 修改用户资料
     * @return
     */

    public Users updateUsers(Users user){
        try {
            getSqlSession().update("updateUser",user);
            sqlSession.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            sqlSession.close();
        }
        return user;
    }