MybatisPlus-实现基于分页的多表关联查询 springboot

MybatisPlus-实现基于分页的多表关联查询介绍
新手入门，目录结构可能不够严谨，我这边没有用mybatis-plus自带的代码生成器，但是大致原理不变，这边我会重点介绍下我踩的坑，比较难找的几个问题，我有单独写在java常见问题里，大家可以去翻阅
1.目录结构这边用红色框出来的，是我这边即将用到的，下面直接上代码

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2.对应文件代码项目/config/MybatisPlusConfig,其中MapeerScan路径记得别写错

@Configuration @MapperScan("com.mk.springboot.mapper") public class MybatisPlusConfig { @Bean public PaginationInterceptor paginationInterceptor() { PaginationInterceptor paginationInterceptor = new PaginationInterceptor(); return paginationInterceptor; } }

项目/pojo/Category.class，这边我有用到lombok，如果没有用到到话，得自己把无参构造，有参构造，getter，setter方法补齐

@Data @AllArgsConstructor @NoArgsConstructor @TableName(value = "https://www.it610.com/article/category") public class Category { @TableId(type = IdType.AUTO) private Integer id; private String name; private Integer articleNum; private Integer plateId; }

项目/mapper/CategoryMapper，一开始我是用注解写的，后面要关联其它表，这边是用xml来写，这边我有两个查询参数，一个是category表的名称name，一个是板块的plate_id

@Repository @Mapper public interface CategoryMapper extends BaseMapper { // @Select("SELECT category.*, plate.`name` as `plateName` FROM category,plate WHERE category.plate_id=plate.id and category.name = #{name} and category.plate_id = #{plate_id}")List getCategoryPlate(Page page, @Param("name") String name, @Param("plateId") Integer plateId); }

项目/resources/mapper/CategoryMapper.xml,这边xml有几个注意事项，如果name为string 类型的话，千万不能在if条件中写name != 0,这样会报错

id="getCategoryPlate" resultType="com.mk.springboot.vo.CategoryPlateVO" > SELECT category.*, plate.`name` as `plateName` FROM category,plate WHERE category.plate_id=plate.id AND category.name = #{name} AND category.plate_id = #{plateId}

项目/service/CategoryService

@Service public interface CategoryService extends IService { Page getCategoryPlate(Page page ,String name, Integer plateId); }

项目/service/impl/CategoryService

@Service public class CategoryServiceImpl extends ServiceImpl implements CategoryService { @Override public Page getCategoryPlate(Page page ,String name, Integer plateId) { return page.setRecords(this.baseMapper.getCategoryPlate(page, name, plateId)); } }

项目/vo/CategoryPlateVO

@Data public class CategoryPlateVO implements Serializable { @TableId private Integer id; private String name; private Integer articleNum; private Integer plateId; private String plateName; }

项目/controller/CategoryController,这边代码写的有点冗余，功能大致实现了，大家可以自行封装

@RequestMapping("/category/list") @ResponseBody public PageFactory list(HttpServletRequest httpServletRequest) { String name = httpServletRequest.getParameter("name"); String plateIdString = httpServletRequest.getParameter("plateId"); Integer plateId = plateIdString != null && plateIdString != "" ? Integer.valueOf(plateIdString) : null; Integer start = Integer.parseInt(httpServletRequest.getParameter("start")); Integer size = Integer.parseInt(httpServletRequest.getParameter("length")); Integer current = start / size + 1; Page pageParam = new Page<>(current, size); // 当前页，总条数构造 page 对象 Page page = categoryService.getCategoryPlate(pageParam, name, plateId); PageFactory pageFac = new PageFactory(); pageFac.setRecordsFiltered(page.getTotal()); pageFac.setRecordsTotal(page.getTotal()); pageFac.setData(page.getRecords()); return pageFac; }

浅谈 【MybatisPlus-实现基于分页的多表关联查询】这期间还有遇见几个非常愚蠢的问题，折腾了很久，一个yaml的配置问题，一开始我是用mybaits的，后面改成mybatisPlus，但是对应的配置没有更新，导致一直报错，如下