JPA eclipse两个外键@IdClass实现错误

Question

我对Java EE和JPA/Eclipselink非常陌生，所以请耐心听我说。我试图为一个没有主键和两个复合键的表创建一个Id，我试图通过使用IdClass将两个外键标记为复合键来应用我在这里读到的解决方案，但在编译和部署服务器时出现了此错误。

异常描述：组合主键规范无效。主键类[com.owl.server.objects.SaleDetails]和实体bean类[com.owl.server.objects.SaleDetails]中的主键字段或属性的名称必须对应，并且它们的类型必须相同。此外，请确保已为XML中的相应属性指定了ID元素和/或在实体类的相应字段或属性上指定了@ID。。请参阅服务器。有关详细信息，请登录。

我必须将字段类型更改为相同吗？还是有其他方法？

产品表及对应实体

@Entity
@Table(name="products")
public class Product implements Serializable {
    
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   @Column(name = "product_id", nullable = false)
   private String product_id;
   
   // ...
}

销售表及对应实体

@Entity
@Table(name="Sales")
public class Sale implements Serializable{
    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "sale_id", nullable = false)
    private int sale_id;

    // ...
}

Sale\u details表和实体（导致错误）

public class SaleDetails implements Serializable {

    private int saleid_fk;
    private String productid_fk;
    private int quantity_sold;
    private String prescription;
    
    public SaleDetails() {
    }
    
    public SaleDetails(int saleid_fk, String productid_fk, int quantity_sold){
        this.saleid_fk = saleid_fk;
        this.productid_fk = productid_fk;
        this.quantity_sold = quantity_sold;
    }
}

Sale\u details实体类

@Entity
@IdClass(SaleDetails.class)
@Table(name = "sale_Details")
public class Sale_details {
    
   @Id
   private int saleid_fk;
    
   @Id
   private String productid_fk;
}

以下是完整堆栈跟踪错误：

[2020-12-24 11:43:50,553] Artifact server:war exploded: java.io.IOException: com.sun.enterprise.admin.remote.RemoteFailureException: Error occurred during deployment: Exception while preparing the app : Exception [EclipseLink-28018] (Eclipse Persistence Services - 2.7.7.payara-p3): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Predeployment of PersistenceUnit [owlJPA] failed.
Internal Exception: Exception [EclipseLink-7150] (Eclipse Persistence Services - 2.7.7.payara-p3): org.eclipse.persistence.exceptions.ValidationException
Exception Description: Invalid composite primary key specification. The names of the primary key fields or properties in the primary key class [com.owl.server.objects.SaleDetails] and those of the entity bean class [class com.owl.server.objects.Sale_details] must correspond and their types must be the same. Also, ensure that you have specified ID elements for the corresponding attributes in XML and/or an @Id on the corresponding fields or properties of the entity class.. Please see server.log for more details.

Answer 1

您可以使用“派生标识”；这是使用嵌入ID映射关系的方法：

@Embeddable
public class SaleDetailId {
    @Column(name = "product_id")
    String productId;  // corresponds to PK type of Product

    @Column(name = "sale_id")
    int saleId; // corresponds to PK type of Sale 
}


@Entity
@Table(name = "sale_details")
public class SaleDetail {
    @EmbeddedId
    SaleDetailId id;

    // id attribute mapped by join column default 
    @MapsId("saleId") // maps saleId attribute of embedded id 
    @ManyToOne
    private Sale sale;

    // id attribute mapped by join column default 
    @MapsId("productId") // maps productId attribute of embedded id 
    @ManyToOne
    private Product product;

    @Column(name = "quantity_sold")
    private int quantitySold;
    
    public SaleDetails(Sale sale, Product product, int quantity_sold){
        this.sale = sale;
        this.product = product;
        this.quantity_sold = quantity_sold;
    }
    // ...
}

要使用IdClass映射关系，请执行以下操作：

public class SaleDetailId {
    int sale; // matches name of @Id attribute and type of Sale PK 
    String product;  // matches name of @Id attribute and type of Product PK
}


@Entity
@IdClass(SaleDetailId.class)
@Table(name = "sale_details")
public class SaleDetail {

    // id attribute mapped by join column default 
    @Id
    @ManyToOne
    @JoinColumn(name = "sale_id")
    private Sale sale;

    // id attribute mapped by join column default 
    @Id
    @ManyToOne
    @JoinColumn(name = "product_id")
    private Product product;

    @Column(name = "quantity_sold")
    private int quantitySold;
    
    public SaleDetails(Sale sale, Product product, int quantity_sold){
        this.sale = sale;
        this.product = product;
        this.quantity_sold = quantity_sold;
    }
    // ...
}

派生标识在第2.4.1节的JPA 2.2规范中进行了讨论（带有示例）。

Answer 2

Idclass值不应是实体“SaleDetails”的同一类

    @Entity
    @IdClass(PK.class)
    public static class SystemUser{
        @Id
        private String subsystem;

        @Id
        private String username;

        public PK getId(){
            return new PK(subsystem, username);
        }

        public void setId(PK id){
            this.subsystem = id.subsystem;
            this.username = id.username;
        }
    }

    public static class PK implements Serializable {

        private String subsystem;

        private String username;

        public PK(String subsystem, String username) {
            this.subsystem = subsystem;
            this.username = username;
        }
    }