myBatis如何实现对三级嵌套对象赋值？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
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>看完上述内容是否对您有帮助呢？如果还想对相关知识有进一步的了解或阅读更多相关文章，请关注亿速云行业资讯频道，感谢您对亿速云的支持。
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