mybatis-自联表二级菜单

<?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.lanou.dao.admin.MenuMapper">
    <resultMap id="menu" type="com.lanou.entity.admin.Menu">
        <id column="id" property="id"></id>
        <result column="parentId" property="parentId"></result>
        <result column="name" property="name"></result>
        <result column="url" property="url"></result>
        <result column="icon" property="icon"></result>
        <collection column="id" property="secondMenu" ofType="com.lanou.entity.admin.Menu" select="selectSecondMenu">

        </collection>
    </resultMap>
    <select id="selectTopMenu" resultMap="menu">
        select id,parentId,name,url,icon from menu where parentId =0
    </select>

    <select id="selectSecondMenu" resultMap="menu">
         select id,parentId,name,url,icon from menu WHERE parentId=#{id};
    </select>


</mapper>

package com.lanou.entity.admin;

import java.util.List;

public class Menu {
    
    
    private Long id;
    private Long parentId;
    private String name;
    private String url;
    private String icon;
    private List<Menu> secondMenu;

    public List<Menu> getSecondMenu() {
    
    
        return secondMenu;
    }

    public void setSecondMenu(List<Menu> secondMenu) {
    
    
        this.secondMenu = secondMenu;
    }

    public Long getId() {
    
    
        return id;
    }

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

    public Long getParentId() {
    
    
        return parentId;
    }

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

    public String getUrl() {
    
    
        return url;
    }

    public void setUrl(String url) {
    
    
        this.url = url;
    }

    public String getName() {
    
    
        return name;
    }

    public void setName(String name) {
    
    
        this.name = name;
    }

    public String getIcon() {
    
    
        return icon;
    }

    public void setIcon(String icon) {
    
    
        this.icon = icon;
    }

    @Override
    public String toString() {
    
    
        return "Menu{" +
                "id=" + id +
                ", parentId=" + parentId +
                ", name='" + name + '\'' +
                ", url='" + url + '\'' +
                ", icon='" + icon + '\'' +
                ", secondMenu=" + secondMenu +
                '}';
    }
}