play framework 2 ebean @manytoone Column specified twice

问题

I'm running to some problems with ebean (using play framework 2 version 2.2.1) I have two classes:

my graph class:

public class Graph extends Model {
     @Id
     @Column(name="id")
     private String id;

     @Column(name="type")
     private String type;

     @OneToMany(mappedBy="valGraph", cascade=CascadeType.ALL)
     private List<Val> valItems; 

and my value class (with Val.graphId foreign key Graph.id):

public class Val extends Model
     @Id
     @Column(name="valId")
     private String valId;  

     @Id
     @Column(name="graphId")
     private String graphId;

     @Column(name="Key")
     private String Key;

     @Column(name="Value")
     private String Value;

     @ManyToOne(fetch = FetchType.LAZY)
     @JoinColumn(name="graphId")
     private Graph valGraph;

but when trying to save a new item i get this error:

javax.persistence.PersistenceException: ERROR executing DML bindLog[] error[Column 'graphId' specified twice]

回答1:

After numerous searchers around the web I found this answer here - thanks to jtal!

Just to summaries the problem:

Using Ebean i have made a @ManyToOne entity that is not implemented in the database in anyway, even more the join field, in my case

graphId

is a valid field that has values of its own.

when trying to join the column on that field, it will always fail because it creates this sql query:

SELECT 
*
FROM
    Val;

select 
    t0.valId c0, 
    t0.graphId c1, 
    t0.Key c2, 
    t0.Value c3, 
    t0.graphId c4 <---- notice this duplicate
from 
    graph_val t0 

in order to solve this, i tell ebean not to use the second set of properties.

my new ebean element looks like this:

@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name="graphId", insertable = false, updatable = false)
private Graph valGraph;

and it works! =)

来源：https://stackoverflow.com/questions/24464812/play-framework-2-ebean-manytoone-column-specified-twice