MybatisPlus自定义 Sql 实现多表查询

概述

编写代码

案例流程说明

控制层

服务层

数据访问层

自定义 SQL

测试

MybatiPlus文档

概述

MyBatis-Plus (opens new window)（简称 MP）是一个 MyBatis (opens new window)的增强具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。在我们实际开发中利用MP 框架，可以简化我们对SQL的编写，提高我们工作效率。这篇文章讲解是MP自定义SQL多表查询详解和一些案例。

愿景

我们的愿景是成为 MyBatis 最好的搭档，就像魂斗罗中的 1P、2P，基友搭配，效率翻倍。

编写代码

案例流程说明

1. 自定义构建多表查询条件语句

用户表关联角色用户关联表和角色表，模糊查询昵称和角色名称
where 自定义条件查询

2. 自定义构建多表 Wrapper 条件语句查询

用户表关联角色用户关联表和角色表，模糊查询昵称和角色名称
Wrapper 自定义条件查询

控制层

/*** <p>* 自定义分页查询* </p>** @author LiPing.Zou* @since 2021-03-05*/
@RestController
@RequiredArgsConstructor
@RequestMapping("/page")
@Api(value = "PageController", tags = "分页模块")
public class PageController {private final AdminService adminService;@GetMapping("getAdminPage")@ApiOperation(value = "获取用户分页列表")public Result<Pager<AdminResp>> getAdminPage(@RequestParam(value="pageNumber",defaultValue = "1") @ApiParam(name="pageNumber",value="当前第几页(从第一页开始)",required = true) Integer pageNumber,@RequestParam(value="pageSize",defaultValue = "10") @ApiParam(name="pageSize",value="每页多少条",required = true) Integer pageSize,@RequestParam(value="roleName",required = false) @ApiParam(name="roleName",value="角色名称") String roleName){return Result.success(adminService.getAdminPage(pageNumber,pageSize,roleName));}@GetMapping("getAdminPageByWraaper")@ApiOperation(value = "获取用户分页列表ByWraaper")public Result<Pager<AdminResp>> getAdminPageByWraaper(@RequestParam(value="pageNumber",defaultValue = "1") @ApiParam(name="pageNumber",value="当前第几页(从第一页开始)",required = true) Integer pageNumber,@RequestParam(value="pageSize",defaultValue = "10") @ApiParam(name="pageSize",value="每页多少条",required = true) Integer pageSize,@RequestParam(value="roleName",required = false) @ApiParam(name="roleName",value="角色名称") String roleName){return Result.success(adminService.getAdminPageByWraaper(pageNumber,pageSize,roleName));}}

服务层

说明：QueryWrapper 包装类查询，对应的字段必须是数据里面字段（如果你的表用了别名查询，查询对象字段最好别名.字段），如果没有匹配上，会报SQL错误

@Overridepublic Pager<AdminResp> getAdminPage(Integer pageNumber, Integer pageSize, String roleName) {log.info("getAdminPage.req pageNumber={},pageSize={},roleName={}",pageNumber,pageSize,roleName);IPage<AdminResp> page = new Page<>(pageNumber, pageSize);IPage<AdminResp> pageData = adminMapper.pageData(page,roleName);if (CollectionUtils.isNotEmpty(pageData.getRecords())) {return new Pager<>(pageNumber,pageSize,(int)pageData.getPages(),pageData.getTotal(),pageData.getRecords());}return new Pager<>();}@Overridepublic Pager<AdminResp> getAdminPageByWraaper(Integer pageNumber, Integer pageSize, String roleName) {log.info("getAdminPage.req pageNumber={},pageSize={},roleName={}",pageNumber,pageSize,roleName);IPage<AdminResp> page = new Page<>(pageNumber, pageSize);QueryWrapper<AdminResp> queryWrapper = Wrappers.query(new AdminResp());if (StringUtils.isNotBlank(roleName)) {queryWrapper.like("ua.nick_name",roleName).or().like("ur.`name`",roleName);}IPage<AdminResp> pageData = adminMapper.getAdminPageByWraaper(page,queryWrapper);if (CollectionUtils.isNotEmpty(pageData.getRecords())) {return new Pager<>(pageNumber,pageSize,(int)pageData.getPages(),pageData.getTotal(),pageData.getRecords());}return new Pager<>();}

数据访问层


/*** <p>* 后台用户表 Mapper 接口* </p>** @author SurRen* @since 2021-02-02*/
public interface AdminMapper extends BaseMapper<Admin> {/** * 自定义分页查询* @param page* @param roleName* @date: 2021/12/10 15:04* @return: com.baomidou.mybatisplus.core.metadata.IPage<com.zlp.dto.AdminResp> */IPage<AdminResp> pageData(IPage<AdminResp> page, String roleName);/** * Wrapper 包装类查询条件* @param page* @param queryWrapper* @date: 2021/12/10 15:03* @return: com.baomidou.mybatisplus.core.metadata.IPage<com.zlp.dto.AdminResp>*/IPage<AdminResp> getAdminPageByWraaper(IPage<AdminResp> page, @Param(Constants.WRAPPER) QueryWrapper<AdminResp> queryWrapper);
}

自定义 SQL

<select id="pageData" resultType="com.zlp.dto.AdminResp">SELECTua.id as userId,ua.username as username,ua.icon as icon,ua.email as email,ua.nick_name as nickName,ur.`name` as roleName,ua.create_time  as createTimeFROMums_admin uaINNER JOIN ums_admin_role_relation uarr ON ua.id = uarr.admin_idLEFT JOIN ums_role ur on uarr.role_id = ur.id<where><if test="roleName !=null and roleName !=''">and (ua.username like concat('%',#{roleName},'%') or ur.`name` like concat('%',#{roleName},'%'))</if></where></select><select id="getAdminPageByWraaper" resultType="com.zlp.dto.AdminResp">SELECTua.id as userId,ua.username as username,ua.icon as icon,ua.email as email,ua.nick_name as nickName,ur.`name` as roleName,ua.create_time  as createTimeFROMums_admin uaINNER JOIN ums_admin_role_relation uarr ON ua.id = uarr.admin_idLEFT JOIN ums_role ur on uarr.role_id = ur.id${ew.customSqlSegment}</select>

测试

http://127.0.0.1:9080/doc.html#/

调用 /page/getAdminPage 接口

后台打印sql语句，自动帮我们分页

SELECT ua.id as userId, ua.username as username, ua.icon as icon, ua.email as email, ua.nick_name as nickName, ur.`name` as roleName, ua.create_time as createTime FROM ums_admin ua INNER JOIN ums_admin_role_relation uarr ON ua.id = uarr.admin_id LEFT JOIN ums_role ur on uarr.role_id = ur.id WHERE (ua.username like concat('%',?,'%') or ur.`name` like concat('%',?,'%')) LIMIT ?,?

调用 /page/getAdminPageByWraaper 接口

SELECT ua.id as userId, ua.username as username, ua.icon as icon, ua.email as email, ua.nick_name as nickName, ur.`name` as roleName, ua.create_time as createTime FROM ums_admin ua INNER JOIN ums_admin_role_relation uarr ON ua.id = uarr.admin_id LEFT JOIN ums_role ur on uarr.role_id = ur.id WHERE (ua.nick_name LIKE ? OR ur.`name` LIKE ?) LIMIT ?,?

MybatiPlus文档

官方文档里面也做介绍，版本需要大于3.0.7
官方链接：使用 Wrapper 自定义SQL