JPA从复合密钥中查找
我有一门课是这样的JPA从复合密钥中查找,jpa,Jpa,我有一门课是这样的 @Entity public class User{ private String userId; @Id public String getUserId(){ return userId; } public void setUserId(String userId){ this.userId = userId; } } @Embeddible public class RegPk{ private String serial;
@Entity
public class User{
private String userId;
@Id
public String getUserId(){
return userId;
}
public void setUserId(String userId){
this.userId = userId;
}
}
@Embeddible
public class RegPk{
private String serial;
private String userId;
....
}
@Entity
@IdClass(RegPk.class)
public class Registration {
private String userId, serial;
private User user
@Id
@Column(name="SRL_C")
public String getSerial() {return serial;}
public void setSerial(String serial) {this.serial = serial;}
@ManyToOne(cascade={CascadeType.REFRESH})
@JoinColumn(name="USERID", referencedColumnName="USERID", nullable = false)
public User getUser() {return user;}
public void setUser(User user) {this.user = user;}
@Id
@Column(name="USERID", nullable = false)
public String getUserId() {
return userId;
}
public void setUserId(String userId) {
this.userId = userId;
}
}
RegPk pk = new RegPk();
pk.setSerial(dr.getSerial());
pk.setUserId(dr.getUserId());
Registration userOld = em.find(Registration.class, pk);
但是当我试着运行它时,我得到了空值。我发誓我以为我让它工作了所以
1)这种事情可能发生吗?
2.)我做错了什么?是的,如果您使用。否则,将两个不同的字段映射到同一列,这是无效的
javadoc提供了一个与您的情况几乎完全匹配的示例。因此,在这种情况下,我的列注释是否在pk类中?如果仍然返回null,我将按照您所描述的创建第二个示例。也许我做错了什么