java - JPA は、私がアクセスしていない関連エンティティに対して何百もの選択を実行します

Question

私はJPAを学んでおり、予定のあるテーブルを表示する小さなアプリケーションを作成しようとしています.

今のところ、h:dataTable(JSF) を使用して予定の説明を表示するだけですが、何らかの理由で、JPA が予定ごとに 1 つの選択を生成して、関連するCreatorエンティティを取得します。したがって、たとえば、100 件の予定がある場合、このCreatorエンティティへのアクセスを使用していない場合でも、データベースに対して 101 件のクエリが生成されます (1 件は予定を取得するため、1 件は作成者ごとに 1 件)。

これが私のAppointmentエンティティです。Creator主キーではないコードでエンティティを参照していますが、テーブルの構造を変更できません。

@Entity
public class Appointment implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private BigDecimal id;

    private String description;

    private Timestamp date;


    @ManyToOne
    @JoinColumn(name = "APPOINTMENT_CREATOR", referencedColumnName = "USER_CODE")
    private Creator creator;

    // Getters and setters
}

これがCreator実体

@Entity
public class Creator implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private BigDecimal id;

    private String name;

    private String surname;

    @Column(name="USER_CODE")
    private int userCode;


    @OneToMany(mappedBy = "creator")
    private List<Cita> appointments;

    public Appointment addAppointment(Appointment appointment) {
        getAppointments().add(appointment);
        appointment.setCreator(this);

        return appointment;
    }

    public Appointment removeAppointment(Appointment appointment) {
        getAppointments().remove(appointment);
        appointment.setCreator(null);

        return appointment;
    }

    // Getters and setters
}

これは私のDAOです

@Repository
public class AppointmentDAO {
    private EntityManager entityManager;

    @PersistenceContext
    public void setEntityManager(EntityManager em) {
        this.entityManager = em;
    }

    public List<Appointment> findAll() {
        List<Appointment> result = null;
        try {
            result = this.entityManager.createQuery("SELECT a from Appointment a").getResultList();
        } catch (Exception ex) {
        }
        return result;
    }
}

そして、これは私のログからの抜粋です

[EL Finest]: connection: 2013-10-11 16:22:35.406--ServerSession(33459456)--Connection(11062282)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Connection released to connection pool [read].

[EL Finest]: query: 2013-10-11 16:22:35.421--ServerSession(33459456)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Execute query ReadObjectQuery(name="creator" referenceClass=Creator sql="SELECT ID, SURNAME, USER_CODE, NAME FROM CREATOR WHERE (USER_CODE = ?)")

[EL Finest]: connection: 2013-10-11 16:22:35.421--ServerSession(33459456)--Connection(20248250)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Connection acquired from connection pool [read].

[EL Finest]: connection: 2013-10-11 16:22:35.421--ServerSession(33459456)--Thread(Thread["http-bio-8080"-exec-3,5,main]) --reconnecting to external connection pool

[EL Fine]: sql: 2013-10-11 16:22:35.453--ServerSession(33459456)--Connection(3304058)--Thread(Thread["http-bio-8080"-exec-3,5,main])--SELECT ID, SURNAME, USER_CODE, NAME FROM CREATOR WHERE (USER_CODE = ?)
    bind => [7054382]

[EL Finest]: connection: 2013-10-11 16:22:35.515--ServerSession(33459456)--Connection(20248250)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Connection released to connection pool [read].

[EL Finest]: transaction: 2013-10-11 16:22:35.531--UnitOfWork(12558692)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Register the existing object net.turbo.model.entities.Creator@b2e368

[EL Finest]: query: 2013-10-11 16:22:35.531--ServerSession(33459456)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Execute query ReadObjectQuery(name="creator" referenceClass=Creator sql="SELECT ID, SURNAME, USER_CODE, NAME FROM CREATOR WHERE (USER_CODE = ?)")

[EL Finest]: connection: 2013-10-11 16:22:35.531--ServerSession(33459456)--Connection(32578948)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Connection acquired from connection pool [read].

[EL Finest]: connection: 2013-10-11 16:22:35.531--ServerSession(33459456)--Thread(Thread["http-bio-8080"-exec-3,5,main])--reconnecting to external connection pool
[EL Fine]: sql: 2013-10-11 16:22:35.562--ServerSession(33459456)--Connection(13173146)--Thread(Thread["http-bio-8080"-exec-3,5,main])--SELECT ID, SURNAME, USER_CODE, NAME FROM CREATOR WHERE (USER_CODE = ?)
    bind => [7042199]

[EL Finest]: connection: 2013-10-11 16:22:35.64--ServerSession(33459456)--Connection(32578948)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Connection released to connection pool [read].

[EL Finest]: transaction: 2013-10-11 16:22:35.64--UnitOfWork(12558692)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Register the existing object net.turbo.model.entities.Creator@1b0c903

[EL Finest]: query: 2013-10-11 16:22:35.64--ServerSession(33459456)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Execute query ReadObjectQuery(name="creator" referenceClass=Creator sql="SELECT ID, SURNAME, USER_CODE, NAME FROM CREATOR WHERE (USER_CODE = ?)")

[EL Finest]: connection: 2013-10-11 16:22:35.64--ServerSession(33459456)--Connection(7112313)--Thread(Thread["http-bio-8080"-exec-3,5,main])--Connection acquired from connection pool [read].

[EL Finest]: connection: 2013-10-11 16:22:35.64--ServerSession(33459456)--Thread(Thread["http-bio-8080"-exec-3,5,main])--reconnecting to external connection pool
[EL Fine]: sql: 2013-10-11 16:22:35.671--ServerSession(33459456)--Connection(15764427)--Thread(Thread["http-bio-8080"-exec-3,5,main])--SELECT ID, SURNAME, USER_CODE, NAME FROM CREATOR WHERE (USER_CODE = ?)
    bind => [7076961]



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