Mybatis之实现增删改查

在上篇mybatis小程序的基础上，实现增删改查

1、UserMapper接口

package com.lizheng.dao;

import com.lizheng.pojo.User;
import java.util.List;

/**
 * 操作对象数据库的实体
 */
public interface UserMapper {
    //只写方法名，不写方法体，花括号也不行
    //查询所有用户
    List<User> getUserList();
    //根据id查询用户
    User getUserById (int id);
    //增加用户
    int addUser (User user);
    //修改用户
    int modifyUser (User user);
    //根据用户id删除用户
    int deleteUserById (int id);
}
           

2、UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<!--namespace对应全路径下的mapper-->
<mapper namespace="com.lizheng.dao.UserMapper">
<!--  id 对应 重写方法名称-->
<!-- resultType 对应返回类型，list 只写范型-->
    <select id="getUserList" resultType="com.lizheng.pojo.User">
    select * from mybatis.user
    </select>
    <select id="getUserById" parameterType="int" resultType="com.lizheng.pojo.User">
        select * from mybatis.user where id = #{id}
    </select>
<!--    对象中的属性可以直接取出来-->
    <insert id="addUser" parameterType="com.lizheng.pojo.User">
        insert into mybatis.user (id,name,pwd) values (#{id},#{name},#{pwd})
    </insert>
    <update id="modifyUser" parameterType="com.lizheng.pojo.User">
        update mybatis.user set name=#{name},pwd=#{pwd} where id = #{id} ;
    </update>
    <delete id="deleteUserById" parameterType="int" >
        delete from mybatis.user where id = #{id}
    </delete>

</mapper>
           

3、测试类

package com.lizheng.dao;

import com.lizheng.Utils.MybatisUtils;
import com.lizheng.pojo.User;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.List;

//测试
public class UserMapperTest {

    @Test
    public void test(){
        //第一步：获取sqlsession对象
        SqlSession session = MybatisUtils.getSqlSession();
        //执行SQL语句
        UserMapper mapper = session.getMapper(UserMapper.class);
        List<User> userList = mapper.getUserList();
        for (User user : userList) {
            System.out.println(user);
        }
        //关闭sqlSession
        session.close();
    }

    @Test
    public void getUserByIdTest (){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        User user = mapper.getUserById(3);
        System.out.println(user);
        sqlSession.close();
    }

    @Test
    public void addUserTest(){

        //增删改一定要提交事务
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int junjun = mapper.addUser(new User(1, "junjun", "123456"));
        if (junjun > 0 ){
            System.out.println(junjun+"增加成功");
        }
        //提交事务
        sqlSession.commit();
        //关闭sqlsession对象
        sqlSession.close();
    }

    @Test
    public void modifyUserTset(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int doudou = mapper.modifyUser(new User(1, "doudou", "123456"));
        if (doudou > 0) {
            System.out.println("修改成功");
        }
        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void deleteUserByIdTest (){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        int i = mapper.deleteUserById(1);
        if (i>0) {
            System.out.println("删除成功");
        }
        sqlSession.commit();
        sqlSession.close();
    }
}
           

注意：1、增删改查sql语句的写法，多练

           2、增删改需要提交事务，sqlSession.commit()