myBatis实现三级嵌套复杂对象的赋值问题

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 {
  
  @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 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 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 {
  
  @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 {
  
  @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 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 {
  
  @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





  
    
    
    
    
    
    
    
    
    
    
    
    
    
      
    
      
      
      
      
      
      
      
      
      
      
      
    
  

  
  
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
  


-- 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
a.id     as    id,
a.station_id as    station_id,
a.operator_idas    operator_id,
a.equipment_owner_id    as    equipment_owner_id,
a.station_nameas    station_name,
a.country_codeas    country_code,
a.area_code as    area_code,
a.address  as    address,
a.station_telas    station_tel,
a.service_telas    service_tel,
a.station_typeas    station_type,
a.station_status      as    station_status,
a.park_nums as    park_nums,
a.station_lngas    station_lng,
a.station_latas    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_hoursas    busine_hours,
a.busine_hours_in_milliseconds      as    busine_hours_in_milliseconds,
a. electricity_fee     as    electricity_fee,
a. service_feeas    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_idas    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_noas    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_idas    t_f_connector_id ,
c.connector_name      as    t_f_connector_name,
c.connector_type      as    t_f_connector_type,
c.connector_noas    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'

希望为遇到同样需求的同学提供到帮助。

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