Re: [eclipselink-users] Persisting a Unidirectional OneToMany fails

[Alon Gamliel <gamliela@xxxxxxxxxxx>]

Hi Chris,

I saw your response in Stack Overflow, thank you.
Yes, the foreign key is not NULL in database, and I understand now this was the problem.
However I couldn't find this demand in spec (JPA2), so in some way it is a bug, and as such I think it should be noted clearly in user-guide.
I'm not sure regular users as myself are exposed and able to understand the link you presented...

-----Original Message-----
From: eclipselink-users-bounces@xxxxxxxxxxx [mailto:eclipselink-users-bounces@xxxxxxxxxxx] On Behalf Of Christopher Delahunt
Sent: Thursday, October 18, 2012 5:34 PM
To: eclipselink-users@xxxxxxxxxxx
Subject: Re: [eclipselink-users] Persisting a Unidirectional OneToMany fails

Hello,

As I tried to point out in the stack overflow post, EclipseLink will update the foreign key in a second statement.  This is stated in the design doc for the feature, specifically under Additional_improvements_to_consider here:
http://wiki.eclipse.org/EclipseLink/Development/JPA2.0/uni-directional_onetomany_mapping#Additional_improvements_to_consider

Feel free to file a bug to have these two statements merged into one if there isn't one, but for now, the feature requires a second statement and so you will need to either remove the not-null constraint, or delay constraint processing until the end of the transaction if your database is capable of it.

Best Regards,
Chris

On 18/10/2012 11:08 AM, Alon Gamliel wrote:
> I'm trying to persist a very simple Unidirectional One to Many relationship, but EclipseLink (2.3.1) fails. Is this a bug or just a stupid mistake? my code is very simple. I also posted a bug on this issue, but it was rejected and I didn't understand the reason (https://bugs.eclipse.org/bugs/show_bug.cgi?id=391279).
>
> Service Class (Parent):
> -------------------------
>
> @Entity
> @Table(name = "tbl_service2")
> public class Service implements Serializable {
>
>      @Id
>      @GeneratedValue(strategy = GenerationType.IDENTITY)
>      @Column(name="service_id")
>      public long serviceID;
>
>      @Column(name="name")
>      public String name;
>
>      @OneToMany(cascade={CascadeType.ALL})
>      @JoinColumn(name="service_id", referencedColumnName="service_id")
>      public Set<Parameter>  parameters; }
>
> Parameter Class (Child):
> -------------------------
> (Of course there is "service_id" foreign key field in the database, which is not represented in the class, as it's unidirectional relation).
>
> @Entity
> @Table(name = "tbl_service_parameters2") public class Parameter 
> implements Serializable {
>
>      @Id
>      @GeneratedValue(strategy = GenerationType.IDENTITY)
>      @Column(name="param_id")
>      public long parameterID;
>
>      @Column(name="name")
>      public String name;
> }
>
> And this is the code:
> -------------------------
>
>      Service service = new Service();
>      service.parameters = new HashSet<Parameter>();
>      service.name = "test";
>      Parameter param = new Parameter();
>      param.name = "test";
>      service.parameters.add(param);
>      em.persist(service);
>      em.flush();
>
>
> I get this excaption:
> -------------------------
>
> Internal Exception: java.sql.SQLException: Field 'service_id' doesn't 
> have a default value Error Code: 1364
> Call: INSERT INTO tbl_service_parameters2 (name) VALUES (?)
>      bind =>  [test]
>
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