CategoryController

    @GetMapping("/detail")
    public Result<Category> detail(Integer id){
        Category c = categoryService.findById(id);
        return Result.success(c);
    }

CategoryService

    //根据id查询分类信息
    Category findById(Integer id);

CategoryServiceImpl

    @Override
    public Category findById(Integer id) {
       Category c = categoryMapper.findById(id);
       return c;
    }

CategoryMapper

    //根据id查询
    @Select("select * from category where id = #{id}")
    Category findById(Integer id);

完成：