JPA OneToMany 关系中的查询无法按预期工作

Question

Given the following Questionnaire entity...

@Entity
@Table(name = "questionnaire")
@EntityListeners(AuditingEntityListener.class)
@Getter
@Builder
@EqualsAndHashCode
@NoArgsConstructor
@AllArgsConstructor
public class Questionnaire {

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

  ...

  @Builder.Default
  @OneToMany(
      mappedBy = "questionnaire",
      fetch = FetchType.LAZY,
      cascade = {CascadeType.ALL})
  private List<Definition> definitionVersions = new ArrayList<>();
}

... and the following Definition entity:

@Entity
@Table(name = "definition")
@IdClass(VersionPk.class)
@EntityListeners(AuditingEntityListener.class)
@Getter
@Setter
@Builder
@EqualsAndHashCode
@NoArgsConstructor
@AllArgsConstructor
public class Definition implements Comparable<Definition>, Persistable<Long> {

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

  @Id
  @Column(name = "version", nullable = false)
  private Integer version;

  ...

  @ManyToOne
  @JoinColumn(name = "definition_id", nullable = false, referencedColumnName = "id")
  private Questionnaire questionnaire;

  @Builder.Default
  @OneToMany(
      mappedBy = "definition",
      fetch = FetchType.LAZY,
      cascade = {CascadeType.ALL})
  private List<Questionnaire> questionnaires = new ArrayList<>();
}

... and for completeness:

@AllArgsConstructor
@NoArgsConstructor
@Getter
@Setter
@Builder
@EqualsAndHashCode
public class VersionPk implements Serializable {

  private Long id;
  private Integer version;
}

For instance, the mechanism above is just to manage many versions of the same questionnaire. Now let's suppose I want to retrieve version 2 of a questionnaire... here below is my custom query:

@Repository
public interface QuestionnaireRepository extends JpaRepository<Questionnaire, Long> {

  String QUERY_FIND_BY_ID_AND_VERSION =
    "select q from Questionnaire q"
      + " join q.definitionVersions v"
      + " where q.id = ?1 and v.version = ?2";

  @Query(value = QUERY_FIND_BY_ID_AND_VERSION)
  Optional<Questionnaire> findByIdAndVersion(Long id, Integer version);

  ...
}

I'd expect that definitionVersions in Questionnaire contains only the specified Definition version; instead, I always get all the definitions associated with a given Questionnaire . Am I missing something?

Answer 1

You are filtering for a questionnaire that has version=2, but the questionnaire you are fetching isn't complete unless it contains all the details (and definitions) that you've mapped to it. JPA does not apply the filters to the query results themselves - some JPA providers allow hooks to do so, but this generally causes issues when the managed entity is 'saved' back, as the data within it is incomplete.

If you want only the definition/questionaire pair, put them in your query for selection:

String QUERY_FIND_BY_ID_AND_VERSION =
    "select v, q from Questionnaire q"
      + " join q.definitionVersions v"
      + " where q.id = ?1 and v.version = ?2";

This will then return a list holding a Object[2], containing a Definition and Questionnaire for each result that matches. Use that Definition instead of accessing the Questionnaire's definitionVersions list.