此处以一对多，条件分页查询为例：

一.表结构：

主表

CREATE TABLE `t_user` (  `id` bigint NOT NULL AUTO_INCREMENT,  `user_name` varchar(255) DEFAULT NULL COMMENT '用户名',  `sex` tinyint DEFAULT NULL,  `email` varchar(255) DEFAULT NULL COMMENT '邮箱',  `phone` varchar(12) DEFAULT NULL COMMENT '手机号',  `passWord` varchar(255) DEFAULT NULL COMMENT '密码',  `is_delete` tinyint(2) unsigned zerofill DEFAULT '00',  `create_time` datetime DEFAULT NULL,  `update_time` datetime DEFAULT NULL,  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

明细表

CREATE TABLE `t_user_detail` (  `id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键id',  `user_id` bigint NOT NULL COMMENT 't_user表主键id',  `address` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci DEFAULT NULL COMMENT '住址',  `hobby` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL COMMENT '爱好',  PRIMARY KEY (`id`)) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci COMMENT='用户详情表';

二.代码实现：

0.请求dto

import io.swagger.annotations.apiModelProperty;import lombok.Data;@Datapublic class PageQuery {    @ApiModelProperty("页数据条数")    public Integer pageSize = 10;    @ApiModelProperty("当前为第几页")    public Integer currentPage = 1;}

import io.swagger.annotations.ApiModelProperty;import lombok.Data;import lombok.EqualsAndHashCode;@Data@EqualsAndHashCodepublic class UserInfoPageDTO extends PageQuery {    @ApiModelProperty("用户名")    private String userName;    private Integer sex;    @ApiModelProperty("邮箱")    private String email;    @ApiModelProperty("手机号")    private String phone;    @ApiModelProperty("爱好")    private String hobby;}

Controller 层：

@RestController@RequestMapping("/user")public class UserController {    //用户表读的service    @Resource    @Qualifier("userServiceWriteImpl")    private IUserService userWService;    //用户表写的service    @Resource    @Qualifier("userServiceReadImpl")    private IUserService userRService;        @PostMapping("/userInfoPage")    public IPage<UserVO> findByPage(@RequestBody UserInfoPageDTO dto) {        return userRService.findByPage(dto);    }}

注：我的项目中进行了service 读写分类配置，实际使用中，直接使用mybatis-plus中的 IUserService 对应的接口就行。
2.service 层

public interface IUserService extends IService<User> {    IPage<UserVO> findByPage(UserInfoPageDTO dto);}

service impl实现层：

import com.baomidou.mybatisplus.core.metadata.IPage;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;import com.up.openfeign.api.user.dto.UserInfoPageDTO;import com.up.openfeign.api.user.vo.UserVO;import com.up.user.entity.User;import com.up.user.mapper.UserMapper;import com.up.user.service.IUserService;import org.springframework.stereotype.Service;import javax.annotation.Resource;@Service@DS("slave")public class UserServiceReadImpl extends ServiceImpl<UserMapper, User> implements IUserService {    @Resource    private UserMapper userMapper;    @Override    public IPage<UserVO> findByPage(UserInfoPageDTO dto) {        Page<UserVO> page = new Page<>(dto.currentPage, dto.pageSize);        IPage<UserVO> queryVoPage = userMapper.findByPage(page, dto);        return queryVoPage;    }}

mapper 层

import com.baomidou.mybatisplus.core.metadata.IPage;import com.baomidou.mybatisplus.extension.plugins.pagination.Page;import com.up.openfeign.api.user.dto.UserInfoPageDTO;import com.up.openfeign.api.user.vo.UserVO;import com.up.user.entity.User;import com.baomidou.mybatisplus.core.mapper.BaseMapper;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.annotations.Param;@Mapperpublic interface UserMapper extends BaseMapper<User> {    IPage<UserVO> findByPage(Page<UserVO> page, @Param("dto") UserInfoPageDTO dto);}

mapper.xml层

DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "Http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.up.user.mapper.UserMapper">    <resultMap id="page_user_vo" type="com.up.openfeign.api.user.vo.UserVO">        <id column="id" jdbcType="BIGINT" property="id"/>        <result column="user_name" jdbcType="VARCHAR" property="userName"/>        <result column="sex" jdbcType="TINYINT" property="sex"/>        <result column="email" jdbcType="VARCHAR" property="email"/>        <result column="phone" jdbcType="VARCHAR" property="phone"/>        <result column="password" jdbcType="VARCHAR" property="password"/>        <result column="is_delete" jdbcType="TINYINT" property="isDelete"/>        <result column="create_time"  property="createTime"/>        <result column="update_time"  property="updateTime"/>                <collection property="details" ofType="com.up.openfeign.api.user.vo.UserDetailVO">                        <id column="udId" jdbcType="BIGINT" property="id"/>            <result column="user_id" jdbcType="BIGINT" property="userId"/>            <result column="address" jdbcType="VARCHAR" property="address"/>            <result column="hobby" jdbcType="VARCHAR" property="hobby"/>        collection>    resultMap>    <select id="findByPage" resultMap="page_user_vo" parameterType="com.up.openfeign.api.user.dto.UserInfoPageDTO">        select u.id,u.user_name,u.sex,u.email,u.phone,u.password,u.is_delete,u.create_time,u.update_time,        ud.id as udId,ud.user_id,ud.address,ud.hobby from t_user u left join t_user_detail ud on u.id=ud.user_id        <where>            <if test="dto.userName !='' and dto.userName != null">                and u.user_name = #{dto.userName,jdbcType=VARCHAR}            if>            <if test="dto.sex != null">                and u.sex = #{dto.sex,jdbcType=TINYINT}            if>            <if test="dto.email !='' and dto.email != null">                and u.email = #{dto.email,jdbcType=VARCHAR}            if>            <if test="dto.phone != null and dto.phone!='' ">                and u.phone = #{dto.phone,jdbcType=VARCHAR}            if>            <if test="dto.hobby != null and dto.hobby!='' ">                and ud.hobby = #{dto.hobby,jdbcType=VARCHAR}            if>        where>    select>mapper>

测试：

结果body:

{    "records": [        {            "id": 2,            "userName": "hc",            "sex": 1,            "email": "46494588@qq.com",            "phone": "18062731203",            "password": "123456",            "isDelete": 0,            "createTime": "2022-08-04T13:59:38.000+0000",            "updateTime": "2022-08-04T14:00:56.000+0000",            "details": [                {                    "id": 3,                    "userId": 2,                    "address": "上海",                    "hobby": "足球"                }            ]        },        {            "id": 1,            "userName": "hc1",            "sex": 2,            "email": "46494588@qq.com",            "phone": "18062731203",            "password": "123456",            "isDelete": 0,            "createTime": "2022-10-20T06:35:12.000+0000",            "updateTime": "2022-10-21T06:35:15.000+0000",            "details": [                {                    "id": 4,                    "userId": 1,                    "address": "北京",                    "hobby": "足球"                }            ]        }    ],    "total": 2,    "size": 10,    "current": 1,    "orders": [],    "optimizeCountsql": true,    "searchCount": true,    "countId": null,    "maxLimit": null,    "pages": 1}

Q:todo page 分页会把details个数也计入总数，后面修复，再补博客

来源地址：https://blog.csdn.net/huangchong0107/article/details/127427061