Hibernate generates ghost entries for new child entities

Question

I have a weird (to me anyway) issue with Hibernate which I can't make any sense of. The code below is my attempt at modeling a ManyToOne relation with an attribute between the entities Case and Suggestion using an additional entity CaseToSuggestion with Case being my aggregate root:

@Entity
@Table(name = "sga_cases")
public class Case {

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

    // Business key
    @Column(name = "caseid", unique = true, nullable = false)
    private String caseId;

    ...

    @OneToMany(mappedBy = "associatedCase", orphanRemoval = true, cascade = CascadeType.ALL)
    private Set<CaseToSuggestion> associatedSuggestions = new HashSet<CaseToSuggestion>();

    ...
}


@Entity
@Table(name = "sga_suggestions")
public class Suggestion {

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

    @Column(name = "suggestionid", unique = true, nullable = false)
    private String suggestionId;

    @Column(name = "localizationkey", nullable = false)
    private String localizationKey;

    @OneToMany(mappedBy = "associatedSuggestion", orphanRemoval = true, cascade = CascadeType.ALL)
    private Set<CaseToSuggestion> caseMapping = new HashSet<CaseToSuggestion>();

    ...
}


@Entity
@Table(name = "sga_case2suggestion")
public class CaseToSuggestion {

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

    @Column(name = "feedback")
    private float feedback;

    @ManyToOne
    @JoinColumn(name = "caseid")
    private Case associatedCase;

    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "suggestionid")
    private Suggestion associatedSuggestion;

   ...
}

If I create new objects for the above entities, set the appropriate associations and then store them with the EntityManager everything works fine:

Case c = new Case(...)
Suggestion sugg = new Suggestion(...);
CaseToSuggestion case2sugg = new CaseToSuggestion(c, sugg, 1.0f);

c.getAssociatedSuggestions().add(case2sugg);
sugg.getAssociatedCases().add(case2sugg);

Followed by entityManager.persist(c);

If I want to add a new association to a Case that is already in the database I retrieve the Case and Suggestion entities I want to associate from the EntityManager and add them to a new CaseToSuggestion:

CaseToSuggestion c2s = new CaseToSuggestion(c, s, fb);
c.getAssociatedSuggestions().add(c2s);
s.getAssociatedCases().add(c2s);

Followed by entityManager.merge(c);

The the CaseToSuggestion entity is stored in the database but for every entry I get a "ghost entry" with a new generated id and all fields null:

+----+----------+--------+--------------+
| id | feedback | caseid | suggestionid |
+----+----------+--------+--------------+
|  3 |        1 |      3 |            1 |
|  4 |        1 |      4 |            2 |
|  5 |        1 |      5 |            2 |
|  6 |        0 |   NULL |         NULL |
|  7 |        1 |      6 |            2 |
|  8 |        0 |   NULL |         NULL |
|  9 |        1 |      7 |            2 |
| 10 |        0 |   NULL |         NULL |
+----+----------+--------+--------------+

Does anybody have an idea what might cause this?

Answer 1

OK, I got it. Removing the OneToMany-Mapping in Suggestion altogether solved the problem for me.