第二十二章第三节：商品服务：发布商品 获取分类关联的品牌信息

1、定义需要返回的数据vo

com.applesnt.onlinemall.product.vo.BrandVo

package com.applesnt.onlinemall.product.vo;
import lombok.Data;
@Data
public class BrandVo {
    /*品牌id*/
    private Long brandId;
    /*品牌名字*/
    private String brandName;
}

2、定义品牌查询接口

com.applesnt.onlinemall.product.service.CategoryBrandRelationService

    List<BrandEntity> getBrandsByCatId(Long catId);

3、定义品牌查询接口实现

com.applesnt.onlinemall.product.service.impl.CategoryBrandRelationServiceImpl

    /*注入分类品牌dao层*/
    @Autowired
    CategoryBrandRelationDao relationDao;
    
    /*注入品牌service*/
    @Autowired
    BrandService brandService;

     @Override
    public List<BrandEntity> getBrandsByCatId(Long catId) {
        /*先从关联表中查询所有的品牌id和名字*/
        List<CategoryBrandRelationEntity> catelogids = relationDao.selectList(new QueryWrapper<CategoryBrandRelationEntity>()
                .eq("catelog_id", catId));

        /*根据查询出来的品牌id封装完整的品牌信息*/
        List<BrandEntity> collect = catelogids.stream().map((obj) -> {
            Long brandId = obj.getBrandId();
            BrandEntity brandEntity = brandService.getById(brandId);
            return brandEntity;
        }).collect(Collectors.toList());
        return collect;
    }

4、controller调用

com.applesnt.onlinemall.product.controller.CategoryBrandRelationController

    @GetMapping("/brands/list")
    public R relationBrandsList(@RequestParam(value = "catId",required = true) Long catId){

        /*返回品牌实体类数据，不直接返回自己定义的brandvo，以便其他业务调用*/
        List<BrandEntity> brandVos = categoryBrandRelationService.getBrandsByCatId(catId);

        /*封装成自己需要的数据*/
        List<BrandVo> collect = brandVos.stream().map((brand) -> {
            BrandVo brandVo = new BrandVo();
            brandVo.setBrandId(brand.getBrandId());
            brandVo.setBrandName(brand.getName());
            return brandVo;
        }).collect(Collectors.toList());

        return R.ok().put("data",collect);
    }