Spring boot（二）递归查询商品分类集合实现

怼烎@ 2023-01-01 14:57 107阅读 0赞

#### 查询商品顶级（父级）分类 ####

*  实体商品分类对象

@Data
    public class Category { 
        private Integer id;
    
        private Integer parentId;
    
        private String name;
    
        private Boolean status;
    
        private Integer sortOrder;
    
        private Date createTime;
    
        private Date updateTime;
    }

*  vo类

@Data
    public class CategoryVo { 
    
    	private Integer id;
    
    	private Integer parentId;
    
    	private String name;
    
    	private Integer sortOrder;
    
    	private List<CategoryVo> subCategories;
    }

@Override
    	public ResponseVo<List<CategoryVo>> selectAll() { 
    		//查询商品分类集合
    		List<Category> categories = categoryMapper.selectAll();
    		//获取顶级分类集合
    		//实现jdk8的 lambda + stream
    		List<CategoryVo> categoryVoList=categories.stream()
    				.filter(x->x.getParentId().equals(ROOT_PARENT_ID)) //判断是否为父级分类
    				.map(x-> category2CategoryVo(x)) //对象copy
    	  .sorted(Comparator.comparing(CategoryVo::getSortOrder).reversed()) //排序
    				.collect(Collectors.toList()); //收集到集合中
    
    		//查询子目录
    		findSubCategory(categoryVoList, categories);
    
    		return ResponseVo.success(categoryVoList);
    	}

*  对象copy方法

private CategoryVo category2CategoryVo(Category category) { 
    	CategoryVo categoryVo = new CategoryVo();
    	BeanUtils.copyProperties(category, categoryVo);//spring 自带copy工具方法
    	return categoryVo;
    }

#### 查询子级分类方法实现 ####

/** * 查询子级分类 * @param categoryVoList 父级分类集合 * @param categories 所以的商品分类集合 */
    private void findSubCategory(List<CategoryVo> categoryVoList, List<Category> categories) { 
    		for (CategoryVo categoryVo : categoryVoList) { 
    			List<CategoryVo> subCategoryVoList = new ArrayList<>();
    			for (Category category : categories) { 
    				//如果查到内容，设置subCategory, 继续往下查
    				if (categoryVo.getId().equals(category.getParentId())) { 
    					CategoryVo subCategoryVo = category2CategoryVo(category);
    					subCategoryVoList.add(subCategoryVo);
    				}
    				subCategoryVoList.sort(Comparator.comparing(CategoryVo::getSortOrder).reversed());//对根据对象字段sortOrder对集合进行排序（不要求排序的忽略）
    				categoryVo.setSubCategories(subCategoryVoList);
    				//递归查询（查询当前分类是否还有子级）
    				findSubCategory(subCategoryVoList, categories);
    			}
    		}
    	}

#### 表结构 ####

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#### 表数据 ####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM5ODE4MzI1_size_16_color_FFFFFF_t_70 1]

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