Get Id of the associated object after save

Question

There is simple model of associated entities:

MainModel class

@Entity 
@Table(name = "main_model")
public class MainModel 
{
    @Id 
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    private long id;

    @OneToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
    @JoinColumn(name = "id_main_model", referencedColumnName = "id")
    private List<AssociatedModel> am_collection;

    public MainModel() { }

    public long getId()
    {
        return this.id;
    }

    public void addAssociated(AssociatedModel am)
    {
        am_collection.add(am);
    }
}

AssociatedModel class

@Entity 
@Table(name = "associated_model")
public class AssociatedModel
{
    @Id 
    @GeneratedValue(strategy = GenerationType.IDENTITY) 
    private long id;

    public AssociatedModel() { }

    public long getId()
    {
        return this.id;
    }
}

Simplest jpa repository for MainModel

public interface MainModelDAO extends JpaRepository<MainModel, Long>  
{
}

and finally, controller's method for creating and saving AssociatedModel instance

@RequestMapping("/url")
public String createAssociated(@RequestParam("id_mainmodel") long id_mainmodel, @RequestBody AssociatedModel newAm) 
{
    MainModel mm = MainModelDAOobject.findOne(id_mainmodel);// MainModelDAOobject - @Autowired
    mm.addAssociated(newAm);
    MainModelDAOobject.saveAndFlush(mm);
    return String.valueOf(newAm.getId());// get Id of associated saved object
}

Associated obect saves into database correctly, but id value of this object, allowed by its getId() method, always zero. How can I get Id of the saved associated object correctly?

this will not solve your problem, but spring-data is pretty cool! have a look at it. — Philipp Sander, Jan 29 '14 at 16:22

score 1 · Answer 1 · edited May 23 '17 at 12:03

1

Try calling MainModelDAOobject.flush() after saving the value, but before reading the ID.

See this answer for an explanation.

Edit: try manually saving newAm by adding a new line:

mm.addAssociated(newAm); // Existing line
newAm = MainModelDAOobject.save(newAm); // New line
MainModelDAOobject.save(mm); // Existing line

edited May 23 '17 at 12:03

Community

1
1

answered Jan 29 '14 at 16:18

David Levesque

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This is not clear for me. I'm not use EntityManager. – gorill Jan 29 '14 at 16:39
Ok, I assume you're using Spring Data JPA then? Edited my answer. – David Levesque Jan 29 '14 at 17:12
Yes, I'm using Spring Data JPA and I tried MainModelDAO.flush() - this has no effect – gorill Jan 29 '14 at 17:15
Yes, I did both: mm = MainModelDAOobject.save(mm); MainModelDAOobject.flush(); – gorill Jan 29 '14 at 17:27
Yeah, that's what I think. See my last edit. This is my last try before I give up! – David Levesque Jan 29 '14 at 17:31
This can't be done, because repository parameterized by MainModel - JpaRepository – gorill Jan 29 '14 at 17:36

score 0 · Answer 2 · answered Jan 29 '14 at 16:05

0

you need a sequencegenerator:

@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "MainModel SequenceGenerator")
@SequenceGenerator(name = "MainModel SequenceGenerator", sequenceName = "MainModel Sequence", initialValue = SEQUENCE_INITIAL_VALUE, allocationSize = SEQUENCE_ALLOCATION_SIZE)

answered Jan 29 '14 at 16:05

Philipp Sander

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Ids for the created records generates correctly in the database. I just cant get them after save. – gorill Jan 29 '14 at 16:11

gorill · Answer 3 · 2014-01-29T17:54:53.220

-1

Thanks to David Levesque for helpful suggestion.

problem is solved as follows:

need additional repository for AssotiatedModel

public interface AssotiatedModelDAO extends JpaRepository {}
then just save associated object manually:

mm.addAssociated(newAm);

newAm = AssotiatedModelDAOobject.save(newAm);

newAm = MainModelDAOobject.save(newAm)`;

MainModelDAOobject.save(mm);

edited Jan 29 '14 at 17:54

answered Jan 29 '14 at 17:49

gorill

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Get Id of the associated object after save

3 Answers3