java - Hibernate 为新的子实体生成 ghost 条目

Question

我对 Hibernate 有一个奇怪的(无论如何对我来说)问题，我无法理解。下面的代码是我尝试使用一个附加实体 CaseToSuggestion 与实体 Case 和 Suggestion 之间的属性对 ManyToOne 关系进行建模，其中 Case 是我的聚合根:

@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;

   ...
}

如果我为上述实体创建新对象，设置适当的关联，然后将它们存储在 EntityManager 中，一切正常:

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

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

紧随其后的是 entityManager.persist(c);

如果我想向数据库中已有的案例添加新关联，我会从 EntityManager 中检索我想关联的案例和建议实体，并将它们添加到新的 CaseToSuggestion:

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

紧随其后的是 entityManager.merge(c);

CaseToSuggestion 实体存储在数据库中，但对于每个条目，我都会得到一个“幽灵条目”，其中包含新生成的 ID，所有字段均为空:

+----+----------+--------+--------------+
| 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 |
+----+----------+--------+--------------+

有人知道是什么原因造成的吗？

Answer 1

好的，我知道了。删除建议中的 OneToMany-Mapping 完全解决了我的问题。