Three-level classification of goods and services (1)-code realization

First, take a look at the renderings:

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The following is the classification table of the product classification stored in the database

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Field explanation:

parent_cId: The cat_id of the parent category.

cat_level: Classification level

sort: Priority, the smaller the higher the priority

analysis

Because the classification has a parent-child relationship, like a tree structure, it is necessary to add an attribute to the bean class of the classification to point to the sub-category.

	/**
	 * 子分类List集合
	 */
	@TableField(exist = false)
	private List<CategoryEntity> children;

In order to form a tree structure, it is necessary to increase the List collection to save the sub-categories. The TableFiled(exist = false)function is to declare that this attribute does not exist in the database

Code

service:

public List<CategoryEntity> listWithTree() {
      
      
        //1、查出所有分类
        List<CategoryEntity> entities = baseMapper.selectList(null);
        //2、组装成具有父子关系的树形结构(因为要形成树形结构，所以要有一个List的属性来存子分类)
        //2.1、找到所有一级分类（parentId == 0）
        List<CategoryEntity> level1Menus = entities.stream().filter(e ->
                e.getParentCid() == 0
        ).map(e -> {
      
      
            //查找子分类
            e.setChildren(getChildrens(e,entities));
            return e;
        }).sorted((e1,e2) -> {
      
      
            //排序
            return (e1.getSort()==null?0:e1.getSort()) -(e2.getSort()==null?0:e2.getSort());
        }).collect(Collectors.toList());
        return level1Menus;
    }

Recursive method:

/**
     * 递归地在所有分类中找到当前分类的子分类
     * @param currentMenu
     * @param all
     * @return
     */
    private List<CategoryEntity> getChildrens(CategoryEntity currentMenu,List<CategoryEntity> all) {
      
      
        //找到所有子分类并加入到子分类的List中
        List<CategoryEntity> children = all.stream().filter(e -> {
      
      
            return e.getParentCid().intValue() == currentMenu.getCatId().intValue();
        }).map(e -> {
      
      
            //继续找每个子分类的子分类
            e.setChildren(getChildrens(e,all));
            return e;
        }).sorted((e1,e2) -> {
      
      
            //排序
            return (e1.getSort()==null?0:e1.getSort()) -(e2.getSort()==null?0:e2.getSort());
        }).collect(Collectors.toList());

        return children;
    }

to sum up

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