RMI +休眠，客户端如何获取生成的ID

Question

@Entity
public class Record implements Serializable{

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@OneToMany(fetch=FetchType.EAGER)
@Fetch(FetchMode.SUBSELECT)
@Cascade(value={CascadeType.SAVE_UPDATE})
private List<Comment> commentList=new ArrayList<Comment>();

}

---

@Entity
public class Comment implements Serializable{

@Id
@GeneratedValue(strategy=GenerationType.AUTO)
private long id;

@Column(columnDefinition="text")
private String content;
}

I have a Record in my Client, and add SOME comments in the list.
Use the RMI method: void update(Record reocord).
Then at the Server, hibernate save Comments with id=0 into database, and give a generated id.

How can I assign these IDs to Comments in the Client? If not, the other time I call update(Record reocord), Comments will be add twice.


Maybe: Record update(Record reocord), but I think if Record have large data it's not wise.

Answer 1

I faced this issue. If you are autogenerating the primary key (which can be mostly used for normalizing tables), Create a unique Id yourself based on the existing data. Do remember to override hashcode and equals for comparison purposes.