Java 使用jpa计算表中的行数

我试图开发一个函数，用特定的参数计算行数：例如，我想计算客户机为“客户机a”的档案数量，我想将其放入一个表中，第一个案例包含客户机名称，第二个案例包含档案数量 例如 客户a | 5 客户b|12 .... 现在我刚刚编写了一个函数，返回所有行的数量

    public Object countrow(){
    Query query=em.createQuery("SELECT COUNT(d) FROM Dossier d");
   Object resultat= query.getSingleResult();
   System.out.println(resultat);
        return resultat;
}

这是我的实体名为档案：

    package model;

import java.io.Serializable;

import java.math.BigDecimal;

import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@NamedQueries({ @NamedQuery(name = "Dossier.findAll", query = "select o from Dossier o") })
public class Dossier implements Serializable {
    @Column(name = "CAT_PROB", length = 4000)
    private String catProb;
    @Column(length = 4000)
    private String client;
    @Column(length = 4000)
    private String contact;
    @Temporal(TemporalType.DATE)
    @Column(name = "DATE_APPEL")
    private Date dateAppel;
    @Temporal(TemporalType.DATE)
    @Column(name = "DATE_CREATION")
    private Date dateCreation;
    @Temporal(TemporalType.DATE)
    @Column(name = "DATE_FERMERTURE")
    private Date dateFermerture;
    @Column(name = "DEP_ID", length = 4000)
    private String depId;
    @Column(name = "DESCRI_PROB", length = 4000)
    private String descriProb;
    @Column(name = "DUREE_TRAITEMENT")
    private Long dureeTraitement;
    @Column(length = 4000)
    private String etat;
    @Column(name = "FINAL", length = 4000)
    private String final_;
    @Column(name = "HEURE_APPEL", length = 20)
    private String heureAppel;
    @Column(name = "HEURE_FERMETURE", length = 20)
    private String heureFermeture;
    @Id
    @Column(name = "ID_DOSSIER", nullable = false, length = 4000)
    private String idDossier;
    @Column(name = "ING_AFF", length = 4000)
    private String ingAff;
    @Column(length = 4000)
    private String motiftemp;
    @Column(name = "OUVERT_PAR", length = 4000)
    private String ouvertPar;
    @Column(name = "TEL_CONTACT")
    private BigDecimal telContact;
    @Column(name = "TYPE_DOSSIER", length = 4000)
    private String typeDossier;

    public Dossier() {
    }

    public Dossier(String catProb, String client, String contact, Date dateAppel, Date dateCreation,
                   Date dateFermerture, String depId, String descriProb, Long dureeTraitement, String etat,
                   String final_, String heureAppel, String heureFermeture, String idDossier, String ingAff,
                   String motiftemp, String ouvertPar, BigDecimal telContact, String typeDossier) {
        this.catProb = catProb;
        this.client = client;
        this.contact = contact;
        this.dateAppel = dateAppel;
        this.dateCreation = dateCreation;
        this.dateFermerture = dateFermerture;
        this.depId = depId;
        this.descriProb = descriProb;
        this.dureeTraitement = dureeTraitement;
        this.etat = etat;
        this.final_ = final_;
        this.heureAppel = heureAppel;
        this.heureFermeture = heureFermeture;
        this.idDossier = idDossier;
        this.ingAff = ingAff;
        this.motiftemp = motiftemp;
        this.ouvertPar = ouvertPar;
        this.telContact = telContact;
        this.typeDossier = typeDossier;
    }

    public String getCatProb() {
        return catProb;
    }

    public void setCatProb(String catProb) {
        this.catProb = catProb;
    }

    public String getClient() {
        return client;
    }

    public void setClient(String client) {
        this.client = client;
    }

    public String getContact() {
        return contact;
    }

    public void setContact(String contact) {
        this.contact = contact;
    }

    public Date getDateAppel() {
        return dateAppel;
    }

    public void setDateAppel(Date dateAppel) {
        this.dateAppel = dateAppel;
    }

    public Date getDateCreation() {
        return dateCreation;
    }

    public void setDateCreation(Date dateCreation) {
        this.dateCreation = dateCreation;
    }

    public Date getDateFermerture() {
        return dateFermerture;
    }

    public void setDateFermerture(Date dateFermerture) {
        this.dateFermerture = dateFermerture;
    }

    public String getDepId() {
        return depId;
    }

    public void setDepId(String depId) {
        this.depId = depId;
    }

    public String getDescriProb() {
        return descriProb;
    }

    public void setDescriProb(String descriProb) {
        this.descriProb = descriProb;
    }

    public Long getDureeTraitement() {
        return dureeTraitement;
    }

    public void setDureeTraitement(Long dureeTraitement) {
        this.dureeTraitement = dureeTraitement;
    }

    public String getEtat() {
        return etat;
    }

    public void setEtat(String etat) {
        this.etat = etat;
    }

    public String getFinal_() {
        return final_;
    }

    public void setFinal_(String final_) {
        this.final_ = final_;
    }

    public String getHeureAppel() {
        return heureAppel;
    }

    public void setHeureAppel(String heureAppel) {
        this.heureAppel = heureAppel;
    }

    public String getHeureFermeture() {
        return heureFermeture;
    }

    public void setHeureFermeture(String heureFermeture) {
        this.heureFermeture = heureFermeture;
    }

    public String getIdDossier() {
        return idDossier;
    }

    public void setIdDossier(String idDossier) {
        this.idDossier = idDossier;
    }

    public String getIngAff() {
        return ingAff;
    }

    public void setIngAff(String ingAff) {
        this.ingAff = ingAff;
    }

    public String getMotiftemp() {
        return motiftemp;
    }

    public void setMotiftemp(String motiftemp) {
        this.motiftemp = motiftemp;
    }

    public String getOuvertPar() {
        return ouvertPar;
    }

    public void setOuvertPar(String ouvertPar) {
        this.ouvertPar = ouvertPar;
    }

    public BigDecimal getTelContact() {
        return telContact;
    }

    public void setTelContact(BigDecimal telContact) {
        this.telContact = telContact;
    }

    public String getTypeDossier() {
        return typeDossier;
    }

    public void setTypeDossier(String typeDossier) {
        this.typeDossier = typeDossier;
    }
}

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如果是，请接受/投票——如果你的评分正确。接受答案：最好在项目中使用Lombok删除样板代码，与使用Lombok一样，您不需要编写getter setter并为sameif创建构造函数，因此请接受/投票–如果标记正确。接受答案：最好在项目中使用Lombok来删除样板代码，与使用Lombok一样，您不需要编写getter setter并为其创建构造函数