标签:统计 poj dao arch ase 对象 blog var art
现在有一个菜单表,菜单里同时保存有一级菜单和二级菜单,一级菜单的父菜单id字段是null,二级菜单的父菜单id字段保存了它的父菜单的id。在Java中,一个菜单对象里有一个List类型的属性保存它的子菜单。现在需要将数据库中的数据转为Java中菜单兑现的结构。
本文采用Mybatis,编写SQL语句做自连表查询。
名 | 类型 |
---|---|
id | int |
description | varchar |
path | varchar |
parent_menu_id | int |
package com.lpc.labbackend.entity;
import java.util.List;
public class Menu {
private Integer id;
private String description;
private String path;
private List<Menu> childMenus;
//省略构造函数、getter、setter
}
<?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.lpc.labbackend.dao.MenuMapper">
<resultMap id="BaseResultMap" type="com.lpc.labbackend.entity.Menu">
<id column="id" property="id" jdbcType="INTEGER"/>
<result column="description" property="description" jdbcType="VARCHAR"/>
<result column="path" property="path" jdbcType="VARCHAR"/>
<collection property="childMenus" ofType="com.lpc.labbackend.entity.Menu" column="id" select="getChildMenus">
</collection>
</resultMap>
<sql id="Base_Column_List">
id, description, path
</sql>
<select id="getMenu" resultMap="BaseResultMap">
select
<include refid="Base_Column_List"/>
from menu
where parent_menu_id is null
</select>
<select id="getChildMenus" resultMap="BaseResultMap">
select
<include refid="Base_Column_List"/>
from menu
where menu.parent_menu_id = #{id}
</select>
</mapper>
resultMap
标签中用一个collection
标签表示Java里的List,ofType
属性表示这个集合的类型。这个List是通过select
属性使用了一个查询语句获取数据,column
属性是这个查询语句的查询条件。
0: {id: 1, icon: "el-icon-user-solid", description: "账户设置", path: null,…}
id: 1
icon: "el-icon-user-solid"
description: "账户设置"
path: null
childMenus: [{id: 5, icon: null, description: "所有账户", path: "users", childMenus: null}]
0: {id: 5, icon: null, description: "所有账户", path: "users", childMenus: null}
id: 5
icon: null
description: "所有账户"
path: "users"
childMenus: null
1: {id: 2, icon: "el-icon-s-data", description: "信息统计", path: null,…}
2: {id: 3, icon: "el-icon-s-check", description: "申请批准", path: null,…}
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标签:统计 poj dao arch ase 对象 blog var art
原文地址:https://www.cnblogs.com/FatShallot/p/12695990.html