Spring，JPA：如何使用多对多关系桥表设置查询另一个实体下的实体

Posted 2023-03-16

【中文标题】Spring，JPA：如何使用多对多关系桥表设置查询另一个实体下的实体

【英文标题】：Spring, JPA: How to query for Entities under another Entity with a many-to-many relationship bridge table setup

【发布时间】：2021-06-28 04:06:54

【问题描述】：

我对 Spring 还很陌生。我正在尝试使用此 ERD 查询一位捐赠者下的所有捐赠：

捐助者 |----* 协议 *----|捐赠（使用桥接表的多对多关系）

这是我的代码：

Donor.java

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Donor extends Auditable implements Comparable<Donor>
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NotBlank(message = "Cannot have an empty account number field.")
    private String accountNumber;
    private String accountName;
    private String salutation;
    private String donorName;
    private String cellphoneNumber;
    private String emailAddress;
    private String companyTIN;
    private String phone1;
    private String phone2;
    private String faxNumber;
    private String address1;
    private String address2;
    private String address3;
    private String address4;
    private String address5;
    private String companyAddress;
    private LocalDate birthDate;
    private String notes;

    @OneToMany(mappedBy = "donor")
    List<MOA> moaList = new ArrayList<>();
    ...

捐赠.java

@Entity
@Data
@AllArgsConstructor
@NoArgsConstructor
public class Donation extends Auditable implements Comparable<Donation> 
   
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @NotBlank(message = "Cannot have an empty account number field.")
    private String accountNumber;
    private String accountName;
    private String orNumber;
    private String date;
    private Double amount;
    private String notes;
    private String needCertificate;
    private String purposeOfDonation;

    @OneToMany(mappedBy = "donation")
    List<MOA> moaList = new ArrayList<>();
    ...

MOA.java（协议）

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
public class MOA extends Auditable
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;


    @ManyToOne
    @JoinColumn(name = "donor_id")
    @JsonIgnoreProperties("moaList")
    private Donor donor;

    @ManyToOne
    @JoinColumn(name = "donation_id")
    @JsonIgnoreProperties("moaList")
    private Donation donation;

    private String name;
    private String donorAccountNumber;
    private Long foreignDonationId;
    private LocalDate dateSigned;

在我的 DonorRepository 中，我正在尝试进行此查询，我希望它会给我想要的东西：

public interface DonorRepository extends JpaRepository<Donor, Long> 
    ...
    @Query(value = "SELECT * FROM donor WHERE account_number = ?1", nativeQuery = true)
    List<Donation> findDonorsDonations(String accountNumber);
    ...

这给了我一个错误

无法从类型 [java.lang.Object[]] 转换为类型 [com.package.server.domain.Donation] 的值 '1, admin, 2021-04-01 10:29:53.0, admin , 2021-04-01 10:29:53.0, 学校, 123456, null, null, null, null, null, null, null, null, null, John Doe, null, null, null, null, null, Mr. ';嵌套异常是 org

【问题讨论】：

您正在向捐赠者查询，但该方法返回Donation。

【参考方案1】：

您可以使用规范 api 和 SpecificationExecutor。

您必须加入 MAO 捐赠（MAO with Donor）然后查询特定捐赠者的捐赠。