分类管理模块

 

后台_品类接口：

https://gitee.com/imooccode/happymmallwiki/wikis/%E5%90%8E%E5%8F%B0_%E5%93%81%E7%B1%BB%E6%8E%A5%E5%8F%A3?sort_id=9911

如何设计及封装无限层级的树状数据结构
Integer parentId一个变量，当parentId等于0时表示根节点，子节点可以往上加，存在平级节点和后台节点。

package com.mmall.pojo;

import java.util.Date;

public class Category {
    private Integer id;

    private Integer parentId;

    private String name;

    private Boolean status;

    private Integer sortOrder;

    private Date createTime;

    private Date updateTime;

    public Category(Integer id, Integer parentId, String name, Boolean status, Integer sortOrder, Date createTime, Date updateTime) {
        this.id = id;
        this.parentId = parentId;
        this.name = name;
        this.status = status;
        this.sortOrder = sortOrder;
        this.createTime = createTime;
        this.updateTime = updateTime;
    }

    public Category() {
        super();
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getParentId() {
        return parentId;
    }


    public void setParentId(Integer parentId) {
        this.parentId = parentId;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name == null ? null : name.trim();
    }

    public Boolean getStatus() {
        return status;
    }

    public void setStatus(Boolean status) {
        this.status = status;
    }

    public Integer getSortOrder() {
        return sortOrder;
    }

    public void setSortOrder(Integer sortOrder) {
        this.sortOrder = sortOrder;
    }

    public Date getCreateTime() {
        return createTime;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public Date getUpdateTime() {
        return updateTime;
    }

    public void setUpdateTime(Date updateTime) {
        this.updateTime = updateTime;
    }


    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Category category = (Category) o;

        return !(id != null ? !id.equals(category.id) : category.id != null);

    }

    @Override
    public int hashCode() {
        return id != null ? id.hashCode() : 0;
    }
}

递归算法的设计思路

 /**
     * 递归查询本节点的id及孩子节点的id
     * @param categoryId
     * @return
     */
    public ServerResponse<List<Integer>> selectCategoryAndChildrenById(Integer categoryId){
        Set<Category> categorySet = Sets.newHashSet();
        findChildCategory(categorySet,categoryId);


        List<Integer> categoryIdList = Lists.newArrayList();
        if(categoryId != null){
            for(Category categoryItem : categorySet){
                categoryIdList.add(categoryItem.getId());
            }
        }
        return ServerResponse.createBySuccess(categoryIdList);
    }


    //递归算法,算出子节点
    private Set<Category> findChildCategory(Set<Category> categorySet ,Integer categoryId){
        Category category = categoryMapper.selectByPrimaryKey(categoryId);
        if(category != null){
            categorySet.add(category);
        }
        //查找子节点,递归算法一定要有一个退出的条件
        List<Category> categoryList = categoryMapper.selectCategoryChildrenByParentId(categoryId);
        for(Category categoryItem : categoryList){
            findChildCategory(categorySet,categoryItem.getId());
        }
        return categorySet;
    }

如何处理复杂对象排重
用set集合解决，不会存储重复的样本

重写hashcode和equal的注意事项
重写Category类的hashCode方法和equals方法，排除对象重复
进入Category类，alt + insert 键 点击hashCode 和equals方法，只挑选id的值来比较

@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Category category = (Category) o;

        return !(id != null ? !id.equals(category.id) : category.id != null);

    }

    @Override
    public int hashCode() {
        return id != null ? id.hashCode() : 0;
    }