技术教程 myBatis实现三级嵌套复杂对象的赋值问题 正文

myBatis实现三级嵌套复杂对象的赋值问题

2022-07-28,,,

平常我们工作中基本最多两级嵌套，但是有时候难免会遇到三级嵌套的业务场景，笔者最近就碰到了，使用一般的嵌套发现赋值为空，这可难倒了菜逼的我，后来在stackoverflow的帮助下终于搜到了解决办法，完美解决了问题 ，总结一下，方便有需要的同学，下面直接上栗子：

首先上实体类：三级嵌套如下 （电站 -----> 电桩 ---->电枪）

电站实体类 (实体为jpa写法，不影响mybatis的使用)

package com.weima.cecapp.entities;

import lombok.data;
import lombok.noargsconstructor;
import org.hibernate.annotations.batchsize;
import org.hibernate.annotations.genericgenerator;

import javax.persistence.*;
import java.util.collections;
import java.util.list;
import java.util.set;
@noargsconstructor
@data
@entity
@table(name = "station_info")
public class stationinfo {
  /**
   * auto-generated primary key.
   */
  @id
  @generatedvalue(generator = "uuid")
  @genericgenerator(name = "uuid", strategy = "org.hibernate.id.uuidgenerator")
  @column(unique = true, nullable = false, updatable = false)
  private string id;

  @column(name = "station_id")
  private string stationid;

  @column(name = "operator_id")
  private string operatorid;

  @column(name = "equipment_owner_id")
  private string equipmentownerid;

  @column
  private string stationname;

  @column
  private string countrycode;

  @column
  private string areacode;

  @column
  private string address;

  @column
  private string stationtel;

  @column
  private string servicetel;

  @column
  private integer stationtype;

  @column
  private integer stationstatus;

  @column
  private integer parknums;

  @column
  private double stationlng;

  @column
  private double stationlat;

  @column
  private string siteguide;

  @column
  private integer construction;

  @onetomany(fetch = fetchtype.lazy, cascade = {cascadetype.all}, orphanremoval = true, mappedby = "ownerstationinfo")
  private list<stationpicture> pictures;

  @column
  private string matchcars;

  @column
  private string parkinfo;

  @column
  private string businehours;

  @column(name = "busine_hours_in_milliseconds")
  private long businehoursinmilliseconds;

  @column
  private string electricityfee;

  @column
  private string servicefee;

  @column
  private string parkfee;

  @column
  private string payment;

  @column
  private integer supportorder;

  @column
  private string remark;

  @onetomany(fetch = fetchtype.lazy, cascade = {cascadetype.all}, orphanremoval = true, mappedby = "ownerstationinfo")
  @batchsize(size = 20)
  private list<equipmentinfo> equipmentinfos;

}

电站图片实体

package com.weima.cecapp.entities;

import lombok.data;
import lombok.equalsandhashcode;
import lombok.tostring;
import org.hibernate.annotations.genericgenerator;

import javax.persistence.*;

@data
@entity
@equalsandhashcode(of = {"url"})
@tostring(exclude = {"ownerstationinfo"})
@table(name = "station_picture")
public class stationpicture {
  /**
   * auto-generated primary key.
   */
  @id
  @generatedvalue(generator = "uuid")
  @genericgenerator(name = "uuid", strategy = "org.hibernate.id.uuidgenerator")
  @column(unique = true, nullable = false, insertable = true, updatable = false)
  private string id;

  @manytoone(fetch = fetchtype.eager, optional = false)
  @joincolumn(nullable = false, updatable = false)
  private stationinfo ownerstationinfo;

  @column
  private string url;
}

电桩实体类

package com.weima.cecapp.entities;

import lombok.data;
import lombok.equalsandhashcode;
import lombok.tostring;
import org.hibernate.annotations.batchsize;
import org.hibernate.annotations.genericgenerator;

import javax.persistence.*;
import java.text.parseexception;
import java.text.simpledateformat;
import java.util.collections;
import java.util.list;

@data
@entity
@equalsandhashcode(of = {"equipmentid"})
@tostring(exclude = {"ownerstationinfo"})
@table(name = "equipment_info")
public class equipmentinfo {
  /**
   * auto-generated primary key.
   */
  @id
  @generatedvalue(generator = "uuid")
  @genericgenerator(name = "uuid", strategy = "org.hibernate.id.uuidgenerator")
  @column(unique = true, nullable = false, updatable = false)
  private string id;

  @column(name = "equipment_id")
  private string equipmentid;

  @manytoone(fetch = fetchtype.eager, optional = false)
  @joincolumn(nullable = false, updatable = false)
  private stationinfo ownerstationinfo;

  @column(name = "manufacturer_id")
  private string manufacturerid;

  @column
  private string manufacturername;

  @column
  private string equipmentmodel;

  @column
  private string productiondate;

  public string getproductiondate() {
    string format = null;
    if (this.productiondate != null) {
      simpledateformat sdf = new simpledateformat("yyyy-mm-dd");
      try {
        format = sdf.format(sdf.parse(this.productiondate));
      } catch (parseexception e) {
        e.printstacktrace();
      }
      return format;
    }
    return format;
  }

  @column
  private string equipmenttype;

  @onetomany(fetch = fetchtype.lazy, orphanremoval = true, mappedby = "ownerequipmentinfo", cascade = {cascadetype.persist})
  @batchsize(size = 20)
  private list<connectorinfo> connectorinfos;

  @column
  private double equipmentlng;

  @column
  private double equipmentlat;

  @column
  private double power;

  @column
  private string equipmentname;

  @column(name = "equipment_no")
  //cpo's custom equipmentid mostly for evstation
  private string equipmentno;
}

电枪实体类

package com.weima.cecapp.entities;

import lombok.data;
import lombok.equalsandhashcode;
import lombok.tostring;
import org.hibernate.annotations.genericgenerator;

import javax.persistence.*;

@data
@entity
@equalsandhashcode(of = {"connectorid"})
@tostring(exclude = {"ownerequipmentinfo"})
@table(name = "connector_info")
public class connectorinfo {
  /**
   * auto-generated primary key.
   */
  @id
  @generatedvalue(generator = "uuid")
  @genericgenerator(name = "uuid", strategy = "org.hibernate.id.uuidgenerator")
  @column(unique = true, nullable = false, updatable = false)
  private string id;

  @manytoone(fetch = fetchtype.eager, optional = false)
  @joincolumn(nullable = false, updatable = false)
  private equipmentinfo ownerequipmentinfo;

  @column(name = "connector_id")
  private string connectorid;

  @column
  private string connectorname;

  @column
  private integer connectortype;

  @column
  private integer voltageupperlimits;

  @column
  private integer voltagelowerlimits;

  @column
  private integer current;

  @column
  private double power;

  @column
  private string parkno;

  @column
  private integer nationalstandard;

  @column(name = "connector_no")
  //cpo's custom connectorid mostly for evstation
  private string connectorno;
}

mapper 文件的resultmap映射及sql语句的书写，要特别注意映射关系

<?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.hubject.cecapp.mapper.stationinfoanyuemapper">

  <resultmap id="templatelistresp" type="com.hubject.cecapp.entities.equipmentinfo">
    <!-- 充电桩信息-->
    <id column  ="id          " property="id"/>
    <result column="equipment_id     " property="equipmentid"/>
    <result column="equipment_lat     " property="manufacturername"/>
    <result column="equipment_lng     " property="equipmentmodel"/>
    <result column="equipment_model    " property="productiondate"/>
    <result column="equipment_name    " property="manufacturerid"/>
    <result column="equipment_type    " property="equipmenttype"/>
    <result column="manufacturer_id    " property="equipmentlng"/>
    <result column="manufacturer_name   " property="equipmentlat"/>
    <result column="power         " property="power"/>
    <result column="production_date    " property="equipmentname"/>
    <result column="owner_station_info_id " property="equipmentno"/>
      <!-- 充电枪 信息列表 -->
    <collection property="connectorinfos" columnprefix="f_" oftype="com.hubject.cecapp.entities.connectorinfo">
      <id column="id" property="id"/>
      <result column="connector_id" property="connectorid"/>
      <result column="connector_name" property="connectorname"/>
      <result column="connector_type" property="connectortype"/>
      <result column="voltage_upper_limits" property="voltageupperlimits"/>
      <result column="voltage_lower_limits" property="voltagelowerlimits"/>
      <result column="current" property="current"/>
      <result column="power" property="power"/>
      <result column="park_no" property="parkno"/>
      <result column="national_standard" property="nationalstandard"/>
      <result column="connector_no" property="connectorno"/>
    </collection>
  </resultmap>

  <!-- 通用查询映射结果 -->
  <resultmap id="base3resultmap" type="com.hubject.cecapp.entities.stationinfo">
    <result column="id" property="id"/>
    <result column="address" property="address"/>
    <result column="area_code" property="areacode"/>
    <result column="busine_hours" property="businehours"/>
    <result column="construction" property="construction"/>
    <result column="country_code" property="countrycode"/>
    <result column="electricity_fee" property="electricityfee"/>
    <result column="equipment_owner_id" property="equipmentownerid"/>
    <result column="station_id" property="stationid"/>
    <result column="operator_id" property="operatorid"/>
    <result column="station_name" property="stationname"/>
    <result column="station_tel" property="stationtel"/>
    <result column="service_tel" property="servicetel"/>
    <result column="station_type" property="stationtype"/>
    <result column="station_status" property="stationstatus"/>
    <result column="park_nums" property="parknums"/>
    <result column="station_lng" property="stationlng"/>
    <result column="station_lat" property="stationlat"/>
    <result column="site_guide" property="siteguide"/>
    <result column="match_cars" property="matchcars"/>
    <result column="park_info" property="parkinfo"/>
    <result column="busine_hoursin_milliseconds" property="businehoursinmilliseconds"/>
    <result column="service_fee" property="servicefee"/>
    <result column="park_fee" property="parkfee"/>
    <result column="payment" property="payment"/>
    <result column="support_order" property="supportorder"/>
    <result column="remark" property="remark"/>
    <result column="templatelistresp" property="remark"/>
    <collection property="equipmentinfos" columnprefix="t_" resultmap="templatelistresp"/>
  </resultmap>


-- 要特别注意的是 t_f_ 的前缀，这个关乎到映射不映射上的根本。
<select id="queryareaforanyocharging" resultmap="base3resultmap">
    select
       a.id                   as    id,
       a.station_id               as    station_id,
       a.operator_id              as    operator_id,
       a.equipment_owner_id           as    equipment_owner_id,
       a.station_name              as    station_name,
       a.country_code              as    country_code,
       a.area_code               as    area_code,
       a.address                as    address,
       a.station_tel              as    station_tel,
       a.service_tel              as    service_tel,
       a.station_type              as    station_type,
       a.station_status             as    station_status,
       a.park_nums               as    park_nums,
       a.station_lng              as    station_lng,
       a.station_lat              as    station_lat,
       a.site_guide               as    site_guide,
       a. construction             as    construction,
       a.match_cars               as    match_cars,
       a.park_info               as    park_info,
       a.busine_hours              as    busine_hours,
       a.busine_hours_in_milliseconds      as    busine_hours_in_milliseconds,
       a. electricity_fee            as    electricity_fee,
       a. service_fee              as    service_fee,
       a. park_fee               as    park_fee,
       a. payment                as    payment,
       a. support_order             as    support_order,
       a.remark                 as    remark
       ,
       e.id                   as    t_id               ,
       e.equipment_id              as    t_equipment_id          ,
       e.equipment_lat             as    t_equipment_lat         ,
       e.equipment_lng             as    t_equipment_lng         ,
       e.equipment_model            as    t_equipment_model        ,
       e.equipment_name             as    t_equipment_name         ,
       e.equipment_type             as    t_equipment_type         ,
       e.manufacturer_id            as    t_manufacturer_id        ,
       e.manufacturer_name           as    t_manufacturer_name       ,
       e.power                 as    t_power             ,
       e.production_date            as    t_production_date        ,
       e.owner_station_info_id         as    t_owner_station_info_id     ,
       e.equipment_no              as    t_equipment_no
       ,

       c.id                   as    t_f_id             ,
       c.power                 as    t_f_power           ,
       c.current                as    t_f_current          ,
       c.park_no                as    t_f_park_no          ,
       c.connector_id              as    t_f_connector_id        ,
       c.connector_name             as    t_f_connector_name       ,
       c.connector_type             as    t_f_connector_type       ,
       c.connector_no              as    t_f_connector_no        ,
       c.national_standard           as    t_f_national_standard     ,
       c.voltage_lower_limits          as    t_f_voltage_lower_limits    ,
       c.voltage_upper_limits          as    t_f_voltage_upper_limits    ,
       c.owner_equipment_info_id        as    t_f_owner_equipment_info_id

       from station_info a join equipment_info e on a.id = e.owner_station_info_id

         join connector_info c on e.id = c.owner_equipment_info_id

         where a.operator_id='ma59j8yl8'
  </select>
  
  </mapper>

希望为遇到同样需求的同学提供到帮助。

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