【MyBatis学习笔记】resultMap与resultType、parameterMap与 parameterType的整理与个人理解

1、输入映射（往数据库输入）parameterMap（不常用）与 parameterType（常用）

2、输出映射（从数据库输出）resultMap与resultType

parameterType

获取用户详细信息时输入为Long id，在xml文件里parameterType对应的值为Long，

新增用户时输入为User user，在xml文件里parameterType对应的值为User,

修改用户时输入为User user，在xml文件里parameterType对应的值为User，

删除用户时输入的为Long[] ids，Long[]是一个对象数组，在xml文件里parameterType对应的值为String

基本可以得出parameterType与传入数据库的参数基本一致。

parameterMap负责将Java Bean的属性映射成statement的参数

resultMap与resultType

1、resultmap：mybatis中在查询进行select映射的时候，返回类型可以用resultType，也可以用resultMap。

2、resulttype：resultType是直接表示返回类型的，而resultMap则是对外部ResultMap的引用，但是resultType跟resultMap不能同时存在

在代码中可以看出两个查询语句中存在resultMap，印证了第二条中resultMap则是对外部ResultMap的引用这句话，数据表中的列和需要返回的对象的属性可能不完全一致，外部的ResultMap进行结果集映射，正好解决这一问题。

PS：下列代码将导入的依赖删掉了

Controller

package com.zx.controller;

/**
 * Controller
 * @date 2022-11-16
 */
@RestController
@RequestMapping("/com/zx")
public class UserController extends BaseController
{
    @Autowired
    private UserService userService;

    /**
     * 查询用户列表
     */
    @PreAuthorize("@ss.hasPermi('com:zx:list')")
    @GetMapping("/list")
    public AjaxResult list(User user)
    {
        List<User> list = userService.selectUserList(user);
        return AjaxResult.success(list);
    }

    /**
     * 导出用户列表
     */
    @PreAuthorize("@ss.hasPermi('com:zx:export')")
    @Log(title = "用户", businessType = BusinessType.EXPORT)
    @PostMapping("/export")
    public void export(HttpServletResponse response, User user)
    {
        List<User> list = userService.selectUserList(user);
        ExcelUtil<User> util = new ExcelUtil<User>(User.class);
        util.exportExcel(response, list, "用户数据");
    }

    /**
     * 获取用户详细信息
     */
    @PreAuthorize("@ss.hasPermi('com:zx:query')")
    @GetMapping(value = "/{id}")
    public AjaxResult getInfo(@PathVariable("id") Long id)
    {
        return AjaxResult.success(userService.selectUserById(id));
    }

    /**
     * 新增用户
     */
    @PreAuthorize("@ss.hasPermi('com:zx:add')")
    @Log(title = "用户", businessType = BusinessType.INSERT)
    @PostMapping
    public AjaxResult add(@RequestBody User user)
    {
        return toAjax(userService.insertUser(user));
    }

    /**
     * 修改用户
     */
    @PreAuthorize("@ss.hasPermi('com:zx:edit')")
    @Log(title = "用户", businessType = BusinessType.UPDATE)
    @PutMapping
    public AjaxResult edit(@RequestBody User user)
    {
        return toAjax(userService.updateUser(user));
    }

    /**
     * 删除用户
     */
    @PreAuthorize("@ss.hasPermi('com:zx:remove')")
    @Log(title = "用户", businessType = BusinessType.DELETE)
	@DeleteMapping("/{ids}")
    public AjaxResult remove(@PathVariable Long[] ids)
    {
        return toAjax(userService.deleteUserByIds(ids));
    }
}

Service

package com.zx.service;

/**
 * 用户Service接口
 * @date 2022-11-16
 */
public interface UserService 
{
    /**
     * 查询用户
     */
    public User selectUserById(Long id);

    /**
     * 查询用户列表
     */
    public List<User> selectUserList(User user);

    /**
     * 新增用户
     */
    public int insertUser(User user);

    /**
     * 修改用户
     */
    public int updateUser(User user);

    /**
     * 批量删除用户
     */
    public int deleteUserByIds(Long[] ids);

    /**
     * 删除用户信息
     */
    public int deleteUserById(Long id);
}

ServiceImpl

package com.zx.service.impl;

/**
 * 用户Service业务层处理
 * @date 2022-11-16
 */
@Service
public class UserServiceImpl implements UserService 
{
    @Autowired
    private UserMapper userMapper;

    /**
     * 查询用户
     */
    @Override
    public User selectUserById(Long id)
    {
        return userMapper.selectUserById(id);
    }

    /**
     * 查询用户列表
     */
    @Override
    public List<User> selectUserList(User user)
    {
        return userMapper.selectUserList(user);
    }

    /**
     * 新增用户
     */
    @Override
    public int insertUser(User user)
    {
        user.setId(IdUtils.nextId());
        user.setCreateBy(SecurityUtils.getUsername());
        user.setCreateTime(DateUtils.getNowDate());
        return userMapper.insertUser(user);
    }

    /**
     * 修改用户
     */
    @Override
    public int updateUser(User user)
    {
        user.setUpdateBy(SecurityUtils.getUsername());
        user.setUpdateTime(DateUtils.getNowDate());
        return userMapper.updateUser(user);
    }

    /**
     * 批量删除用户
     */
    @Override
    public int deleteUserByIds(Long[] ids)
    {
        return userMapper.deleteUserByIds(ids);
    }

    /**
     * 删除用户信息
     */
    @Override
    public int deleteUserById(Long id)
    {
        return userMapper.deleteUserById(id);
    }
}

Mapper

package com.zx.mapper;

/**
 * 用户Mapper接口
 * @date 2022-11-16
 */
public interface UserMapper 
{
    /**
     * 查询用户
     */
    public User selectUserById(Long id);

    /**
     * 查询用户列表
     */
    public List<User> selectUserList(User user);

    /**
     * 新增用户
     */
    public int insertUser(User user);

    /**
     * 修改用户
     */
    public int updateUser(User user);

    /**
     * 删除用户
     */
    public int deleteUserById(Long id);

    /**
     * 批量删除用户
     */
    public int deleteUserByIds(Long[] ids);
}

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">
<mapper namespace="com.zx.mapper.UserMapper">
    
    <resultMap type="User" id="UserResult">
        <result property="id"    column="id"    />
        <result property="userName"    column="username"    />
        <result property="passWord"    column="password"    />
        <result property="createBy"    column="create_by"    />
        <result property="createTime"    column="create_time"    />
        <result property="updateBy"    column="update_by"    />
        <result property="updateTime"    column="update_time"    />
    </resultMap>

    <sql id="selectUserVo">
        select id, username, password, create_by, create_time, update_by, update_time from user
    </sql>

    <select id="selectUserList" parameterType="User" resultMap="UserResult">
        <include refid="selectUserVo"/>
        <where>  
            <if test="userName != null "> and username = #{userName}</if>
            <if test="passWord != null "> and password = #{passWord}</if>
        </where>
    </select>
    
    <select id="selectUserById" parameterType="Long" resultMap="UserResult">
        <include refid="selectUserVo"/>
        where id = #{id}
    </select>
        
    <insert id="insertUser" parameterType="User">
        insert into user
        <trim prefix="(" suffix=")" suffixOverrides=",">
            <if test="id != null">id,</if>
            <if test="userName != null">username,</if>
            <if test="passWord != null">password,</if>
         </trim>
        <trim prefix="values (" suffix=")" suffixOverrides=",">
            <if test="id != null">#{id},</if>
            <if test="userName != null">#{username},</if>
            <if test="passWord != null">#{password},</if>
         </trim>
    </insert>

    <update id="updateUser" parameterType="User">
        update user
        <trim prefix="SET" suffixOverrides=",">
            <if test="userName != null">username = #{userName},</if>
            <if test="passWord != null">password = #{passWord},</if>
        </trim>
        where id = #{id}
    </update>

    <delete id="deleteUserById" parameterType="Long">
        delete from user where id = #{id}
    </delete>

    <delete id="deleteUserByIds" parameterType="String">
        delete from user where id in 
        <foreach item="id" collection="array" open="(" separator="," close=")">
            #{id}
        </foreach>
    </delete>
</mapper>