Mybatis学习3 增删改查的实现

增删改查简称:CRUD (创建：Create， 读取：Read，更新：Update，删除： Delete) 是对于存储的信息可以进行操作的同义词。是一个对四种操作持久化信息的基本操作的助记符。CRUD 通常是指适用于存于数据库或数据存储器上的信息的操作，不过也可以应用在高层级的应用操作，例如通过在设置状态字段并标记删除的而并非移除数据的伪删除。

注意点：需要提交事务

注意点：需要提交事务

注意点：需要提交事务

接口代码：

package com.gyc.dao;

import com.gyc.pojo.User;

import java.util.List;

public interface UserMapper {
    //获取全部用户
    public List getUserList();

    //根据id查询用户
    public User getUserById(int id);

    //增加一个用户
    public int addUser(User user);

    //修改一个用户
    public int updateUser(User user);

    //删除一个用户
    public int deleteUser(int id);
}

 mapper代码

    
        select * from mybatis.user
    

    
        select * from mybatis.user where id = #{id}
    

    
        insert into mybatis.user (id, name, pwd) values (#{id}, #{name}, #{pwd})
    

    
        update mybatis.user set name=#{name},pwd = #{pwd} where id = #{id};
    

    
        delete from mybatis.user where id = #{id};
    

测试代码：

package com.gyc.dao;

import com.gyc.pojo.User;
import com.gyc.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

public class UserDaoTest {

    @Test
    public void Test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
        List userList = userMapper.getUserList();

        for (User user :  userList){
            System.out.println(user);
        }

        User user = userMapper.getUserById(1);
        System.out.println(user);

        sqlSession.close();
    }

    @Test
    public void addUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        int ret = userMapper.addUser(new User(4, "hello", "123456"));
        if(ret > 0){
            System.out.println("插入成功！");
        }

        User user = userMapper.getUserById(4);
        System.out.println(user);

        //增删改必须提交事务，数据库表中才能看到
        sqlSession.commit();

        sqlSession.close();
    }

    @Test
    public void updateUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        int ret = userMapper.updateUser(new User(4, "hi", "123456"));
        if(ret > 0){
            System.out.println("修改成功！");
        }

        User user = userMapper.getUserById(4);
        System.out.println(user);

        //增删改必须提交事务，数据库表中才能看到
        sqlSession.commit();

        sqlSession.close();
    }

    @Test
    public void deleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserMapper userMapper = sqlSession.getMapper(UserMapper.class);

        int ret = userMapper.deleteUser(4);
        if(ret > 0){
            System.out.println("删除成功！");
        }

        //增删改必须提交事务，数据库表中才能看到
        sqlSession.commit();

        User user = userMapper.getUserById(4);
        System.out.println(user);

        sqlSession.close();
    }
}