在同一实体上的JOIN FETCH之后进行Hibernate额外查询

Question

我试图通过使用此查询来查询大量的实体,尽管Hibernate:

        "Select * " +
        " From Dossier as dossier" +
        " LEFT  JOIN FETCH dossier.candidat as candidat " +
        " LEFT  JOIN FETCH candidat.roles as role " +
        " LEFT  JOIN FETCH dossier.infoPerso as infoPerso " +
        " LEFT  JOIN FETCH dossier.etablissementOrigine as etablissementOrigine " +
        " LEFT  JOIN FETCH etablissementOrigine.filieres as filieres " +
        " LEFT OUTER JOIN FETCH etablissementOrigine.ville as villeOrigine " +
        " LEFT  JOIN FETCH dossier.etatDossier as etatDossier " +
        " LEFT OUTER JOIN FETCH infoPerso.fichierCNIRecto as fichierCNIRecto " +
        " LEFT OUTER JOIN FETCH fichierCNIRecto.type " +
        " LEFT OUTER JOIN FETCH infoPerso.fichierCNIVerso as fichierCNIVerso " +
        " LEFT OUTER JOIN FETCH fichierCNIVerso.type " +
        " LEFT OUTER JOIN FETCH infoPerso.fichierCV as fichierCV " +
        " LEFT OUTER JOIN FETCH fichierCV.type " +
        " LEFT OUTER JOIN FETCH infoPerso.fichierJAPD as fichierJAPD " +
        " LEFT OUTER JOIN FETCH fichierJAPD.type " +
        " LEFT OUTER JOIN FETCH infoPerso.fichierCNIVerso as fichierCNIVerso " +
        " LEFT OUTER JOIN FETCH fichierCNIVerso.type " +
        " LEFT OUTER JOIN FETCH infoPerso.situationFamilliale as situation "


            dossiers = getEntityManager()
                    .createQuery(sql, Dossier.class)
                    .getResultList();

我可以看到hibernate在做第一个大的本机SQL查询.但就在那之后,Hibernate为每一行生成了1个以上的查询来加载DOssier,我不知道为什么,Dossier已经是fetchs元素的一部分......

 /* load org.ema.ecandidature.dossier.Dossier */ select
    dossier0_.id as id1_61_0_,
    dossier0_.version as version2_61_0_,
    dossier0_.valid as valid3_61_0_,
    dossier0_.validSecretariat as validSec4_61_0_,
    dossier0_.candidat_id as candidat7_17_0_,
    dossier0_.casParticulier as casParti1_17_0_,
    dossier0_.dateInscription as dateInsc2_17_0_,
    dossier0_.dateSoumission as dateSoum3_17_0_,
    dossier0_.entreprise_id as entrepri8_17_0_,
    dossier0_.etablissementOrigine_id as etabliss9_17_0_,
    dossier0_.etatDossier_id as etatDos10_17_0_,
    dossier0_.infoPaiement_id as infoPai11_17_0_,
    dossier0_.infoPerso_id as infoPer12_17_0_,
    dossier0_.listCursusAcademique_id as listCur13_17_0_,
    dossier0_.listDocumentsSupplementaires_id as listDoc14_17_0_,
    dossier0_.listExpEntreprise_id as listExp15_17_0_,
    dossier0_.listFormations_id as listFor16_17_0_,
    dossier0_.listLangues_id as listLan17_17_0_,
    dossier0_.listReferents_id as listRef18_17_0_,
    dossier0_.listSejourEtranger_id as listSej19_17_0_,
    dossier0_.motivationCentreInteret_id as motivat20_17_0_,
    dossier0_.secretariatChangeDate as secretar4_17_0_,
    dossier0_.secretariatChangeDateBackup as secretar5_17_0_,
    dossier0_.validationCommentaire as validati6_17_0_ 
from
    Dossier dossier0_ 
where
    dossier0_.candidat_id=?

Dossier.class:

@Entity
@BatchSize(size=100)
public class Dossier extends ValidableEntity {

    /** The Constant serialVersionUID. */
    private static final long serialVersionUID = 1L;

    /** The etablissement origine. */
    @SecretaryExport
    @ManyToOne( fetch=FetchType.LAZY)
    @JoinColumn()
    private Etablissement etablissementOrigine;

    /** The date inscription. */
    @SecretaryExport
    private Date dateInscription;

    /** The date soumission. */
    @SecretaryExport
    private Date dateSoumission;

    /** The date modification. */
    @SecretaryExport
    private Date secretariatChangeDate;

    /** The date de modification backup. */
    @SecretaryExport
    private Date secretariatChangeDateBackup;

    /** The cas particulier. */
    @SecretaryExport
    private Boolean casParticulier;

    /** The etat dossier. */
    @SecretaryExport
    @ManyToOne( fetch=FetchType.LAZY)
    @JoinColumn()
    private EtatDossier etatDossier;

    /** The candidat. */
    @SecretaryExport
    @OneToOne(fetch=FetchType.LAZY)
    private Candidat candidat;

    /** The info perso. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private InfoPerso infoPerso;

    /** The list formations. */
    //@SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private ListFormations listFormations;

    /** The list cursus academique. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private ListCursusAcademique listCursusAcademique;

    /** The motivation centre interet. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private MotivationCentreInteret motivationCentreInteret;

    /** The entreprise. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private Entreprise entreprise;

    /** The list langues. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private ListLangues listLangues;

    /** The list sejour etranger. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private ListSejourEtranger listSejourEtranger;

    /** The list exp entreprise. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private ListExpEntreprise listExpEntreprise;

    /** The list referents. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL},fetch=FetchType.LAZY,orphanRemoval = true)
    private ListReferents listReferents;

    /** The info paiement. */
    @SecretaryExport
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL},fetch=FetchType.LAZY,orphanRemoval = true)
    private InfoPaiement infoPaiement;

    /** The avis jury. */
    @OneToMany(mappedBy= "dossier" , cascade = { CascadeType.ALL},fetch=FetchType.LAZY,orphanRemoval = true)
    private Set<AvisJury> avisJury = new HashSet<>();

    /** The list documents supplementaires. */
    @Obligatoire
    @ObligatoireSecretariat
    @OneToOne(cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private ListDocumentsSupplementaires listDocumentsSupplementaires;

    /** The list fichier. */
    @OneToMany(mappedBy = "dossier", cascade = { CascadeType.ALL },fetch=FetchType.LAZY,orphanRemoval = true)
    private Set<Fichier> listFichier;

    /** The list avis examinateur. */
    @OneToMany(mappedBy= "dossier" , cascade = { CascadeType.ALL},fetch=FetchType.LAZY,orphanRemoval = true)
    private Set<AvisExaminateur> listAvisExaminateur;

    /** The list commentaire. */
    @OneToMany(cascade = { CascadeType.ALL},fetch=FetchType.LAZY,orphanRemoval = true)
    private Set<Commentaire> listCommentaire;

    /** The validation commentaire. */
    @Column(length = 500)
    @Pattern(regexp="^(.|\n|\r|\t)*$")//accepte tous les caractères et les retours lignes
    private String validationCommentaire;

}

这有什么问题？

Answer 1

这有什么问题？

正如我在我的书" 高性能Java持久性"中所解释的那样,除非您打算修改实体,否则永远不应该获取实体.因此,如果您只需要一个只读视图,那么您应该使用DTO投影.

假设您确实需要获取整个图形,因为您计划对其进行修改,那么您必须使用以下提取策略:

您可以获取尽可能多的孩子@OneToOne和@ManyToOne你的第一个查询以及至多一个实体关联@OneToMany或@ManyToMany.

对于剩余的@OneToMany或者@ManyToMany,您必须使用辅助查询.但是,您不希望以N + 1方式执行此操作,因此您需要在传递使用第一个查询获取的根实体时运行JPQL查询.

请记住,如果将二级集合重新组合到根实体上,则会在根实体上触发一些不需要的修改.因此,如果要将根实体传递给Web层,则应以只读模式获取它们.

同样,如果您不需要实体,那么您应该只获取DTO投影并使用a ResultTransfomer将表格式投影转换为DTO图形,如本文所述.

但就在那之后,Hibernate为每一行生成了1个以上的查询来加载DOssier,我不知道为什么,Dossier已经是fetchs元素的一部分......

从这些映射中,不清楚为什么要执行该查询,但您可以在数据源代理级别,在Hibernate中轻松调试它,并查看堆栈跟踪以查看触发它的内容.