如何在视图中添加主键？

Question

I wish to map a database view into a Java object using Hibernate but since I don't have an Id in my view, I can't do it.

How do I set a column in my view as a primary key?

@Entity
@Table(name = "employmentinformationview")
public class EmploymentInformationView implements Serializable {

    //@Id
    //No primary key

    @Column(name = "InfoID")
    private int infoId;

    @Column(name = "EmpID")
    private String empId;

    ...

}

Answer 1

As suggested by Piotr, select a column or set of columns that are unique in your view. If you have a single column that is unique and not null then you can select that as your primary key.

For example, to make empId as primary key, you can try this:

@Id
@Column(name = "EmpID")
private String empId;

But if you have multiple columns that can form as your composite key then you need to create an composite key using @EmbeddedId :

@Entity
@Table(name = "employmentinformationview")
public class EmploymentInformationView implements Serializable {

    @EmbeddedId
    @AttributeOverride(name="infoId", column=@Column(name="InfoID")
    @AttributeOverride(name="empId", column=@Column(name="EmpID")
    EmploymentViewId id;

    ...

}

The composite key is declared as an Embedabble class:

@Embeddable
class EmploymentViewId implements Serializable {
    int infoId;
    String empId;
}