Spring Data JPA 多表关联查询的实现

多表查询在spring data jpa中有两种实现方式，第一种是利用hibernate的级联查询来实现，第二种是创建一个结果集的接口来接收连表查询后的结果。第一种方式需要继承JpaSpecificationExecutor接口，利用Specification 进行复杂查询，还需要定义好表之间的映射关系，比较复杂。所以这里还是介绍第二种比较简单的方式。

一对一映射

创建实体类：

UserInfo类

@Entity
@Data
@Table(name="tb_user")
public class UserInfo implements Serializable {@Id@GeneratedValue(strategy=GenerationType.IDENTITY)private Long userId;private String name;private int age;private String sex;private String email;// 与 Address 的关联private Long addressId;}

Address类

@Entity
@Data
@Table(name = "tb_address")
public class Address {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long addressId;private String areaCode;private String country;private String province;private String city;private String area;private String detailAddress;}

PartViewInfo类(关联查询的结果存储类)

@Data
public class PartViewInfo {private String name;private String areaCode;//满参构造函数public PartViewInfo(String name, String areaCode) {this.name = name;this.areaCode = areaCode;}}

持久层：

AddressRepository接口

public interface AddressRepository extends JpaRepository<Address, Long> {}

UserInfoRepository

public interface UserInfoRepository extends JpaRepository<UserInfo, Long> {@Query("select new com.example.jpatestformanytable.entity.PartViewInfo(u.name, a.areaCode) from UserInfo u, Address a where u.addressId = a.addressId")public List<PartViewInfo> findViewInfo2();
}

测试代码：

@SpringBootTest
public class sdda {@Autowiredprivate UserInfoRepository userInfoRepository;@Autowiredprivate AddressRepository addressRepository;public void init() {Address addr1 = new Address("027","CN","HuBei", "WuHan","WuChang", "123 street");Address addr2 = new Address("023","CN","ChongQing", "ChongQing","YuBei", "123 road");addressRepository.save(addr1);addressRepository.save(addr2);UserInfo user1 = new UserInfo("ZS", 21,"Male","123@xx.com", addr1.getAddressId());UserInfo user2 = new UserInfo("Ww", 25,"Male","234@xx.com", addr2.getAddressId());userInfoRepository.save(user1);userInfoRepository.save(user2);}public void deleteAll() {userInfoRepository.deleteAll();addressRepository.deleteAll();}@Testpublic void testQuery() {init();List<PartViewInfo> partViewInfoList = userInfoRepository.findViewInfo2();for (PartViewInfo partViewInfo : partViewInfoList) {System.out.println(partViewInfo);}deleteAll();}}

测试结果：

使用到的相关sql语句

Hibernate: insert into tb_address (area, area_code, city, country, detail_address, province) values (?, ?, ?, ?, ?, ?)
Hibernate: insert into tb_address (area, area_code, city, country, detail_address, province) values (?, ?, ?, ?, ?, ?)
Hibernate: insert into tb_user (address_id, age, email, name, sex) values (?, ?, ?, ?, ?)
Hibernate: insert into tb_user (address_id, age, email, name, sex) values (?, ?, ?, ?, ?)
Hibernate: select userinfo0_.name as col_0_0_, address1_.area_code as col_1_0_ from tb_user userinfo0_ cross join tb_address address1_ where userinfo0_.address_id=address1_.address_id
Hibernate: select userinfo0_.user_id as user_id1_1_, userinfo0_.address_id as address_2_1_, userinfo0_.age as age3_1_, userinfo0_.email as email4_1_, userinfo0_.name as name5_1_, userinfo0_.sex as sex6_1_ from tb_user userinfo0_
Hibernate: delete from tb_user where user_id=?
Hibernate: delete from tb_user where user_id=?
Hibernate: select address0_.address_id as address_1_0_, address0_.area as area2_0_, address0_.area_code as area_cod3_0_, address0_.city as city4_0_, address0_.country as country5_0_, address0_.detail_address as detail_a6_0_, address0_.province as province7_0_ from tb_address address0_
Hibernate: delete from tb_address where address_id=?
Hibernate: delete from tb_address where address_id=?

得到的结果

PartViewInfo{name='ZS', areaCode='027'}
PartViewInfo{name='Ww', areaCode='023'}

易出问题的地方：

持久层的sql语句中，定义别名后就要全用别名，否则报错。
结果类中，要自定义一个满参数的构造函数，不能靠Lombok。

参考

Spring Data JPA 实现多表关联查询

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Spring Data JPA 多表关联查询的实现

Spring Data JPA 多表关联查询的实现

一对一映射

参考

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