Java Spring 數據 JPA 帶外鍵的復合 ID

Question

我正在制作 Spring web 服務以了解更多信息，我目前正在映射數據庫。 我有一個具有復合 ID 的表，其中一個 ID 是另一個表 (ManytoOne) 的外鍵。

債權人	債權人發票
ID	債權人編號
姓名	發票編號

就像你在任何地方買東西一樣，他們使用自己的方式制作 ID，它有一個像這樣的復合 ID。 我當前的代碼：Serializable class CInvoiceId：

import javax.persistence.Column;
import javax.persistence.Embeddable;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import java.io.Serializable;
import java.util.Objects;

@Embeddable
public class CInvoiceId implements Serializable {
    @ManyToOne
    @JoinColumn(name = "creditors_id", nullable = false)
    private Creditor cInvoiceCreditorId;
    @Column(name = "invoice_id", nullable = false)
    private String cInvoiceId;

    public CInvoiceId(Creditor creditor, String cInvoiceId){
        this.cInvoiceCreditorId = creditor;
        this.cInvoiceId = cInvoiceId;
    }

    //Setters, Getters, Equals and Hash
}

我的債權人 class

import javax.persistence.*;
import java.util.List;

@Entity
@Table(name = "creditors")
public class Creditor {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int creditorId;

    @Column(name = "name",nullable = false)
    private String creditorName;

    @OneToMany(mappedBy = "cInvoiceCreditorId")
    private List<CInvoice> cInvoices;
}

我的 CInvoice class：

import javax.persistence.*;
import java.math.BigDecimal;
import java.util.Date;

@Entity
@Table(name = "c_invoices")
public class CInvoice {
    @EmbeddedId
    private CInvoiceId cInvoiceID;
}

當我啟動它來嘗試測試它時，我收到錯誤消息，它無法找到來自債權人 class 的映射，但我不知道我應該將它 map 設置為什么，因為 ID 現在是在 CInvoiceId class 中生成的。什么應該嗎？

問候丹妮

Answer 1

您可以使用“派生身份”來 map 這些類：

債權人：

@Entity
@Table(name = "creditors")
public class Creditor {
    @Id
    @GeneratedValue
    @Column(name = "id")
    private int id;

    @Column(name = "name",nullable = false)
    private String name;

    @OneToMany(mappedBy = "creditor")
    private List<CInvoice> invoices;
}

C發票編號：

@Embeddable
public class CInvoiceId implements Serializable {
    @Column(name = "invoice_id", nullable = false)
    private String invoiceID;

    private int creditorID; // corresponds to PK type of Creditor

    // ...
}

C發票：

@Entity
@Table(name = "c_invoices")
public class CInvoice {
    @EmbeddedId
    private CInvoiceId id;

    @MapsId("creditorID") // maps creditorID attribute of embedded id
    @ManyToOne
    @JoinColumn(name = "creditors_id", nullable = false)
    Creditor creditor;
}

派生身份在JPA 2.2 規范的第 2.4.1 節中討論（帶有示例）。