@ManyToOne字段在Playframework 2中不起作用

Question

I'm struggling with some persistance issues in the playframework. I don't think what I'm trying to do should be to hard so I can't understand why what I've done just isn't working. I've created an entity which references another entity through a ManyToOne mapping (cv in example below). The main entity is being persisted and the reference entity also appears to be, being persisted. However whenever I load the main entity through a Entity. findAll() method the main entity loads but all the values on the referenced entity are null.

What's even weirder is the main entity appears to have the correct id for the referenced entity it's just not loading. I know this as I'm doing a find.all on both the main entity ( CrossTrade ) and the referenced entity ( CurVal ) when I start up my application and it's finding all the referenced entities with values and the main entity with values. It just for some reason doesn't seem to be picking up the referenced entity values from the CrossTrade entity when I load it. Any help would be much appreciated.

@Entity
@Table(name="CrossTrade")
public class CrossTrade extends Model {

    @Id
    @GeneratedValue
    public Long id;

    @Transient
    public Double quantity = 1.00;

    @ManyToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    public CurVal cv;
 }

@Entity
@Table(name="CurVal")
public class CurVal extends Model{

    @Id
    @GeneratedValue
    public Long id;

    public Double high;
    public Double low;
    public Double fee; 
}

Answer 1

You're not telling Ebean where the ManyToOne reference is mapped to.

Try updating your CurVal class to:

@Entity
@Table(name="CurVal")
public class CurVal extends Model{
    @Id
    @GeneratedValue
    public Long id;

    @OneToMany(mappedBy="cv")
    public Set<CrossTrade> trades;

    public Double high;
    public Double low;
    public Double fee; 
}

Another thing is that having CascadeType.ALL on your ManyToOne is rather broken, since if you delete one CrossTrade , it will also delete the CurVal attached to it, but leaves all other CrossTrades attached to that CurVal as orphans. By all means it should be the other way around, ie, putting the CascadeType.ALL on the OneToMany field.