亲宝软件园·资讯

展开

Mybatis目录树 当Mybatis遇上目录树超全完美解决方案

砖业洋__ 人气:0
想了解当Mybatis遇上目录树超全完美解决方案的相关内容吗,砖业洋__在本文为您仔细讲解Mybatis目录树的相关知识和一些Code实例,欢迎阅读和指正,我们先划重点:Mybatis目录树,下面大家一起来学习吧。

相信你也遇到过这种场景,判断二级目录属于哪个一级目录,一个员工属于哪个上级员工领导…

Mybatis遇上目录树,有哪些解决方法?

一般来说,有xml直接实现和java代码递归赋值实现。

方式一:xml直接实现

这里列出category数据表数据

表结构如下

type表示分类类型,也就是目录级别,1表示一级目录,3表示三级目录

大家就不要关注数据类型规范了,比如这里id应该biginttype明明可以tinyint之类的,我抓我看到的例子直接讲解。

  目录为甜点/蛋糕的id为1,而蛋糕和点心的father_id为1,目录为饼干/膨化的id为2,饼干、薯片、虾条的father_id就是2,一级目录id对应二级子目录的father_id,这就是所属对应关系,可以理解为父子关系。

实体类是mybatis-generator插件自动生成的

public class Category {
    private Integer id;
    private String name;
    private Integer type;
    private Integer fatherId;
    private String logo;
    private String slogan;
    private String catImage;
    private String bgColor;
    //=====篇幅原因,省掉Getter和Setter方法======
	......
}

一般我们看到的商城,鼠标放到一级分类目录就会展示出二级分类目录。我们的需求是当鼠标移动到一级分类,我们需要提供二级分类和三级分类。

这里贴出需要返回给前端的聚合模型view object数据

/**
 * 二级分类VO
 */
public class CategoryVO {
    private Integer id;
    private String name;
    private String type;
    private Integer fatherId;
    // 三级分类vo list
    private List<SubCategoryVO> subCatList;
	//=====篇幅原因,省掉Getter和Setter方法======
	......
}
public class SubCategoryVO {
    private Integer subId;
    private String subName;
    private String subType;
    private Integer subFatherId;
    //=====篇幅原因,省掉Getter和Setter方法======
	......
}

这就涉及到自连接查询子目录的技巧了,我们试试查找father_id1的子分类数据,也就是查询甜点/蛋糕分类下面的二级和三级分类,执行如下语句

SELECT
	f.id AS id,
	f.`name` AS `name`,
	f.type AS type,
	f.father_id AS fatherId,
	c.id AS subId,
	c.`name` AS subName,
	c.type AS subType,
	c.father_id AS subFatherId 
FROM
	category f
	LEFT JOIN category c ON f.id = c.father_id 
WHERE
	f.father_id = 1

结果如下

可以看到二级分类为蛋糕、点心时,有哪些对应的三级分类可以提供给前端,便于展示。

  我这里分为CategoryVOSubCategoryVO ,而不是把所有属性放在一个VO,是为了便于理解。如果不用List集合,而把所有属性放在一个VO,前端收到的数据形式和你此时在数据库查询出来的一样,有多条蛋糕记录,底下对应着不同具体食品,这让前端不好处理也不符合逻辑,正常逻辑应该是只有一个蛋糕分类,然后这个分类里面有数组去装着蛋糕对应子分类才对。

  这里其实只用一个CategoryVO里面也可以处理,在后面第二种方式用java代码处理多级目录时,你会看到我只用了一个CategoryVO就能处理。

注意,二级分类的实体类CategoryVO有个

private List<SubCategoryVO> subCatList;

这个subCatList是为了存放三级分类的vo list,在xml中三级分类用了collection对应这个list

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.me.mapper.CategoryMapperCustom" >
  <resultMap id="myCategoryVO" type="com.me.pojo.vo.CategoryVO">
    <id column="id" property="id"/>
    <result column="name" property="name"/>
    <result column="type" property="type"/>
      <!--
       column一定要在sql语句中找到,property一定要在对应实体类中找到
       因为sql用as写了别名,所以column才能用fatherId,如果不用别名,还是得写father_id
       -->
    <result column="fatherId" property="fatherId"/>

    <!--
      collection 标签:用于定义关联的list集合类型的封装规则
      property:对应三级分类的list属性名
      ofType:集合的类型,三级分类的vo
    -->
    <collection property="subCatList" ofType="com.me.pojo.vo.SubCategoryVO">
      <id column="subId" property="subId"/>
      <result column="subName" property="subName"/>
      <result column="subType" property="subType"/>
      <result column="subFatherId" property="subFatherId"/>
    </collection>
  </resultMap>

  <select id="getSubCatList" resultMap="myCategoryVO" parameterType="int">
    SELECT
        f.id as id,
        f.`name` as `name`,
        f.type as type,
        f.father_id as fatherId,
        c.id as subId,
        c.`name` as subName,
        c.type as subType,
        c.father_id as subFatherId
    FROM
        category f
    LEFT JOIN
        category c
    on
        f.id = c.father_id
    WHERE
        f.father_id = #{rootCatId}
  </select>
</mapper>

首先让前端展示在首页的一级分类,前端调用一级分类接口,我们只需要查询type1的数据返回给前端,鼠标移动到一级分类,就调用获取子分类的接口,前端传入对应一级分类的id给后端,后端将这个id作为father_id去查询子分类。最后我们可以调用getSubCatList来得到所有目录。

  @Transactional(propagation = Propagation.SUPPORTS)
    @Override
    public List<CategoryVO> getSubCatList(Integer rootCatId) {
        return categoryMapperCustom.getSubCatList(rootCatId);
    }

最后数据就是这样,如下

{
	"status": 200,
	"msg": "OK",
	"data": [{
		"id": 11,
		"name": "蛋糕",
		"type": "2", <==================type=2表示二级目录
		"fatherId": 1,
		"subCatList": [{
			"subId": 37,
			"subName": "蒸蛋糕",
			"subType": "3", <================subType=3表示3级目录
			"subFatherId": 11
		}, {
			"subId": 38,
			"subName": "软面包",
			"subType": "3",
			"subFatherId": 11
		}, {
			"subId": 39,
			"subName": "脱水蛋糕",
			"subType": "3",
			"subFatherId": 11
		}, {
			"subId": 40,
			"subName": "马卡龙",
			"subType": "3",
			"subFatherId": 11
		}, {
			"subId": 41,
			"subName": "甜甜圈",
			"subType": "3",
			"subFatherId": 11
		}, {
			"subId": 42,
			"subName": "三明治",
			"subType": "3",
			"subFatherId": 11
		}, {
			"subId": 43,
			"subName": "铜锣烧",
			"subType": "3",
			"subFatherId": 11
		}]
	}, {
		"id": 12,
		"name": "点心",
		"type": "2",
		"fatherId": 1,
		"subCatList": [{
			"subId": 44,
			"subName": "肉松饼",
			"subType": "3",
			"subFatherId": 12
		}, {
			"subId": 45,
			"subName": "华夫饼",
			"subType": "3",
			"subFatherId": 12
		}, {
			"subId": 46,
			"subName": "沙琪玛",
			"subType": "3",
			"subFatherId": 12
		}, {
			"subId": 47,
			"subName": "鸡蛋卷",
			"subType": "3",
			"subFatherId": 12
		}, {
			"subId": 48,
			"subName": "蛋饼",
			"subType": "3",
			"subFatherId": 12
		}, {
			"subId": 49,
			"subName": "凤梨酥",
			"subType": "3",
			"subFatherId": 12
		}, {
			"subId": 50,
			"subName": "手撕面包",
			"subType": "3",
			"subFatherId": 12
		}]
	}]
}

方式二:java代码递归处理二级三级目录

此刻我换一个数据库例子,但是还是和上面一个处理一级二级三级分类的例子一样
数据表如下

表结构如下

和上一个例子大同小异,type依然表示目录级别

此刻需要返回给前端的VO如下,此刻我只写了一个CategoryVO,没有写子VO,可以对比前一种方式看看,道理都是一样的。

public class CategoryVO {
    private Integer id;
    private String name;
    private Integer type;
    private Integer parentId;
    private Integer orderNum;
    private Date createTime;
    private Date updateTime;
    private List<CategoryVO> childCategory = new ArrayList<>();
    //=====篇幅原因,省掉Getter和Setter方法======
	......
}
  @Override
    public List<CategoryVO> listCategoryForCustomer(Integer parentId) {
        ArrayList<CategoryVO> categoryVOList = new ArrayList<>();
        recursivelyFindCategories(categoryVOList, parentId);
        return categoryVOList;
    }
	// 以该parentId对应的目录为根节点,查询下面所有子目录信息,categoryVOList是要返回给前端展示的聚合模型数据
    private void recursivelyFindCategories(List<CategoryVO> categoryVOList, Integer parentId) {
        // 递归获取所有子类别,并组合成为一个"目录树"
        List<Category> list= categoryMapper.selectCategoriesByParentId(parentId); // 通过父id查询子分类
        if (!CollectionUtils.isEmpty(list)) {
            for (int i = 0; i < list.size(); ++i) {
                Category category = list.get(i);
                CategoryVO categoryVO = new CategoryVO();
                BeanUtils.copyProperties(category, categoryVO);
                categoryVOList.add(categoryVO);
                // 这里当前目录id作为下一次的父id,查询有没有对应的子目录,getChildCategory()方法是返回定义的List<CategoryVO> childCategory
                recursivelyFindCategories(categoryVO.getChildCategory(), categoryVO.getId());
            }
        }
    }

XML文件如下:

......
  <resultMap id="BaseResultMap" type="com.me.mall.model.pojo.Category">
    <id column="id" jdbcType="INTEGER" property="id" />
    <result column="name" jdbcType="VARCHAR" property="name" />
    <result column="type" jdbcType="INTEGER" property="type" />
    <result column="parent_id" jdbcType="INTEGER" property="parentId" />
    <result column="order_num" jdbcType="INTEGER" property="orderNum" />
    <result column="create_time" jdbcType="TIMESTAMP" property="createTime" />
    <result column="update_time" jdbcType="TIMESTAMP" property="updateTime" />
  </resultMap>
  <sql id="Base_Column_List">
    id, `name`, `type`, parent_id, order_num, create_time, update_time
  </sql>
  <select id="selectCategoriesByParentId" parameterType="int" resultMap="BaseResultMap">
    select <include refid="Base_Column_List"/>
    from category
    where parent_id = #{parentId}
  </select>
  ......

我们手动查询模拟一下递归的过程,首先查询parent_id3的二级分类

select *
from category
where parent_id = 3

在这里插入图片描述

结果递归查询的时候,又会发现parent_id=4时还有数据,即还有三级分类,我们手动查询试试

select *
from category
where parent_id = 4

在这里插入图片描述

示例数据如下:

{
    "status": 10000,
    "msg": "SUCCESS",
    "data": [
        {
            "id": 4,
            "name": "橘子橙子",
            "type": 2, <=================代表二级目录
            "parentId": 3,
            "orderNum": 1,
            "createTime": "2019-12-17T17:17:00.000+0000",
            "updateTime": "2019-12-28T08:25:10.000+0000",
            "childCategory": [ <===============代表还有三级目录
                {
                    "id": 19,
                    "name": "果冻橙",
                    "type": 3,
                    "parentId": 4,
                    "orderNum": 1,
                    "createTime": "2019-12-17T17:17:00.000+0000",
                    "updateTime": "2020-02-10T16:37:02.000+0000",
                    "childCategory": []
                }
            ]
        },
        {
            "id": 11,
            "name": "草莓",
            "type": 2,
            "parentId": 3,
            "orderNum": 2,
            "createTime": "2019-12-17T17:17:00.000+0000",
            "updateTime": "2019-12-28T07:44:42.000+0000",
            "childCategory": []
        },
        {
            "id": 12,
            "name": "奇异果",
            "type": 2,
            "parentId": 3,
            "orderNum": 3,
            "createTime": "2019-12-17T17:17:00.000+0000",
            "updateTime": "2019-12-28T08:25:12.000+0000",
            "childCategory": []
        },
        {
            "id": 14,
            "name": "车厘子",
            "type": 2,
            "parentId": 3,
            "orderNum": 4,
            "createTime": "2019-12-17T17:17:00.000+0000",
            "updateTime": "2019-12-28T08:25:12.000+0000",
            "childCategory": []
        },
        {
            "id": 28,
            "name": "其他水果",
            "type": 2,
            "parentId": 3,
            "orderNum": 4,
            "createTime": "2019-12-17T17:17:00.000+0000",
            "updateTime": "2019-12-28T08:25:12.000+0000",
            "childCategory": []
        }
    ]
}

加载全部内容

相关教程
猜你喜欢
用户评论