树形结构sql查询封装

版权声明： https://blog.csdn.net/qq_27721169/article/details/86541187

xml文件

<?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.macro.mall.dao.PmsProductCategoryDao">
    <resultMap id="listWithChildrenMap" type="com.macro.mall.dto.PmsProductCategoryWithChildrenItem"
               extends="com.macro.mall.mapper.PmsProductCategoryMapper.BaseResultMap">
        <collection property="children" resultMap="com.macro.mall.mapper.PmsProductCategoryMapper.BaseResultMap"
                    columnPrefix="child_"></collection>
    </resultMap>
    <select id="listWithChildren" resultMap="listWithChildrenMap">
        select
            c1.id,
            c1.name,
            c2.id   child_id,
            c2.name child_name
        from pms_product_category c1 left join pms_product_category c2 on c1.id = c2.parent_id
        where c1.parent_id = 0
    </select>
</mapper>

dao文件

public interface PmsProductCategoryDao {
    List<PmsProductCategoryWithChildrenItem> listWithChildren();
}

dto

public class PmsProductCategoryWithChildrenItem extends PmsProductCategory {
    private List<PmsProductCategory> children;

    public List<PmsProductCategory> getChildren() {
        return children;
    }

    public void setChildren(List<PmsProductCategory> children) {
        this.children = children;
    }
}

对应实体map

<resultMap id="BaseResultMap" type="com.macro.mall.model.PmsProductCategory">
    <id column="id" jdbcType="BIGINT" property="id" />
    <result column="parent_id" jdbcType="BIGINT" property="parentId" />
    <result column="name" jdbcType="VARCHAR" property="name" />
    <result column="level" jdbcType="INTEGER" property="level" />
    <result column="product_count" jdbcType="INTEGER" property="productCount" />
    <result column="product_unit" jdbcType="VARCHAR" property="productUnit" />
    <result column="nav_status" jdbcType="INTEGER" property="navStatus" />
    <result column="show_status" jdbcType="INTEGER" property="showStatus" />
    <result column="sort" jdbcType="INTEGER" property="sort" />
    <result column="icon" jdbcType="VARCHAR" property="icon" />
    <result column="keywords" jdbcType="VARCHAR" property="keywords" />
  </resultMap>

sql

DROP TABLE IF EXISTS `pms_product_category`;
CREATE TABLE `pms_product_category` (
  `id` bigint(20) NOT NULL AUTO_INCREMENT,
  `parent_id` bigint(20) DEFAULT NULL COMMENT '上机分类的编号：0表示一级分类',
  `name` varchar(64) DEFAULT NULL,
  `level` int(1) DEFAULT NULL COMMENT '分类级别：0->1级；1->2级',
  `product_count` int(11) DEFAULT NULL,
  `product_unit` varchar(64) DEFAULT NULL,
  `nav_status` int(1) DEFAULT NULL COMMENT '是否显示在导航栏：0->不显示；1->显示',
  `show_status` int(1) DEFAULT NULL COMMENT '显示状态：0->不显示；1->显示',
  `sort` int(11) DEFAULT NULL,
  `icon` varchar(255) DEFAULT NULL COMMENT '图标',
  `keywords` varchar(255) DEFAULT NULL,
  `description` text COMMENT '描述',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=52 DEFAULT CHARSET=utf8 COMMENT='产品分类';