使用Mybatis进行CRUD

原创已于 2022-02-19 19:40:21 修改 · 371 阅读

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#sql #java #服务器

于 2022-02-19 15:31:45 首次发布

本文介绍了如何通过Map对象在Mybatis中实现插入、更新等操作的灵活性，避免硬编码对象属性。通过map参数，可以更方便地处理复杂数据库字段，提高代码复用性。

实体类

package pojo;

public class User {
    private int id;
    private String name;
    private String password;

    public User() {
    }

    public User(int id, String name, String password) {
        this.id = id;
        this.name = name;
        this.password = password;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

UserDao接口

package dao;

import pojo.User;

import java.util.List;

public interface UserDao {
    //获得所有用户
    public List<User> getUsers();

    //获得指定id的用户
    public User getUserById(int id);

    //添加用户
    public int insertUser(User user);

    //更新用户信息
    public int updateUser(User user);

    //删除用户
    public int deleteUser(int id);
}

Mapper配置文件

<?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">
<mapper namespace="dao.UserDao">
    <select id="getUsers" resultType="pojo.User">
        select * from mybaits.`user`;
    </select>

    <select id="getUserById" parameterType="int" resultType="pojo.User">
        select * from mybaits.user where `id`=#{id};
    </select>

    <insert id="insertUser" parameterType="pojo.User" >
        insert into mybaits.user values(#{id},#{name},#{password});
    </insert>

    <update id="updateUser" parameterType="pojo.User">
        update `user` set `name`=#{name},`password`=#{password} where id=#{id};
    </update>

    <delete id="deleteUser" parameterType="int">
        delete from `user` where id=#{id};
    </delete>
</mapper>

测试类

import dao.UserDao;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pojo.User;
import utils.MybatisUtils;

import java.util.List;

public class UserMapper {
    @Test
    public void test(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        List<User> users = mapper.getUsers();

        for (User user : users) {
            System.out.println(user);
        }
        sqlSession.close();
    }

    @Test
    public void testGetUserById(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        User user = mapper.getUserById(1);
        System.out.println(user.getName());
        sqlSession.close();
    }

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

        UserDao mapper = sqlSession.getMapper(UserDao.class);
        int niuliu = mapper.insertUser(new User(4, "niuliu", "0000000"));
        if(niuliu>0){
            System.out.println("插入成功！");
        }
        sqlSession.commit();
        sqlSession.close();
    }

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

        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.updateUser(new User(4,"kang","000000"));

        sqlSession.commit();
        sqlSession.close();
    }

    @Test
    public void testDeleteUser(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserDao mapper = sqlSession.getMapper(UserDao.class);
        mapper.deleteUser(4);

        sqlSession.commit();
        sqlSession.close();
    }
}

万能Map
我们可以定义一个方法，比如插入一个用户的时候，原本我们是需要传递一个User对象来插入的，但是当我们数据库中的字段多了之后，我们就需要为这个对象添加很多值

//添加用户
    public int insertUser2(Map<String,Object> map);

Mapper配置文件
这里我们需要传入map类型的参数，这么做的好处就是我们去参数的时候可以不需要按照User对象中的严格相同，可以在后面往map中添加

<?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">
<mapper namespace="dao.UserDao">
    <insert id="insertUser2" parameterType="map" >
        insert into mybaits.user values(#{id},#{name},#{password});
    </insert>
</mapper>

测试类
这里创建了一个map集合，然后往map中添加了三个参数

import dao.UserDao;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;
import pojo.User;
import utils.MybatisUtils;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class UserMapper {
    @Test
    public void testInsertUser2(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        UserDao mapper = sqlSession.getMapper(UserDao.class);
        Map<String,Object> map=new HashMap<>();
        map.put("id",4);
        map.put("name","hello");
        map.put("password","000000");

        int i = mapper.insertUser2(map);


        if(i>0){
            System.out.println("插入成功！");
        }
        sqlSession.commit();
        sqlSession.close();
    }
}