JPA - 多對一級聯

Question

我有兩個實體

ServiceDownload.java

@Entity 
public class ServiceDownload implements Serializable { 
    private static final long serialVersionUID = -5336424090042137820L; 

@Id 
@GeneratedValue 
private Long id; 
@Length(max = 255) 
private String description; 

private byte[] download; 

private String fileName; 

@ManyToOne 
private Service service; 

Service.java

@Entity 
public class Service implements Serializable { 
    private static final long serialVersionUID = 4520872456865907866L; 


@EmbeddedId 
private ServiceId id; 

@Length(max = 255) 
private String servicename; 

@Column(columnDefinition = "text") 
private String highlightsText; 
@Column(columnDefinition = "text") 
private String detailsText; 
@Column(columnDefinition = "text") 
private String productText; 
@Column(columnDefinition = "text") 
private String dataText; 

@ManyToMany(mappedBy = "services") 
private Set<Machine> machines; 

@OneToMany(targetEntity = ServiceDownload.class) 
private List<ServiceDownload> serviceDownloads; 

@OneToOne 
private ServicePicture servicePicture; 

當我創建一個新的ServiceDownload對象，並嘗試挖牆角這個我收到重複的密鑰異常。看起來jpa試圖在服務表中插入一個新的服務對象。我如何禁用此行爲？

Answer 1

您正在爲@Id使用@GeneratedValue註釋。根據JPA文檔，你應該提供唯一標識符

默認情況下，應用程序負責提供和設置實體標識符（請參閱@Id）

嘗試使用@SequenceGenerator，並在你的序列數據庫生成唯一的標識符