java - USE JpaWhere 带有列表 := Key-6ren

java - USE JpaWhere 带有列表 := Key

转载作者：行者123 更新时间：2023-12-01 10:34:35

我想使用列表对象执行 SQL JPA 查询，但是当我尝试时出现以下错误消息:

Cannot be resolved to a valid type.

我将 JPA 与 Maven 一起使用。我想这样做:

@Entity
@Table(name = "Personne")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Personne.findAll", query = "SELECT p FROM Personne p"),
    @NamedQuery(name = "Personne.findByKeyClient", query = "SELECT p FROM Personne p WHERE p.keyClient = :keyClient"),
     @NamedQuery(name = "Personne.CountPersonne", query = "SELECT COUNT(p) FROM Personne p WHERE p.sessionCollection.keySession = :keySession "),
    @NamedQuery(name = "Personne.findByNom", query = "SELECT p FROM Personne p WHERE p.nom = :nom"),
    @NamedQuery(name = "Personne.findByPrenom", query = "SELECT p FROM Personne p WHERE p.prenom = :prenom"),
    @NamedQuery(name = "Personne.findByEmail", query = "SELECT p FROM Personne p WHERE p.email = :email"),
    @NamedQuery(name = "Personne.findByTelephone", query = "SELECT p FROM Personne p WHERE p.telephone = :telephone"),
    @NamedQuery(name = "Personne.findByPortable", query = "SELECT p FROM Personne p WHERE p.portable = :portable"),
    @NamedQuery(name = "Personne.findByFax", query = "SELECT p FROM Personne p WHERE p.fax = :fax"),
    @NamedQuery(name = "Personne.findByDateModification", query = "SELECT p FROM Personne p WHERE p.dateModification = :dateModification"),
    @NamedQuery(name = "Personne.findByDateCreation", query = "SELECT p FROM Personne p WHERE p.dateCreation = :dateCreation"),
    @NamedQuery(name = "Personne.findByActif", query = "SELECT p FROM Personne p WHERE p.actif = :actif")})
public class Personne implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "KeyClient")
    private String keyClient;
    @Size(max = 255)
    @Column(name = "Nom")
    private String nom;
    @Size(max = 255)
    @Column(name = "Prenom")
    private String prenom;
    // @Pattern(regexp="[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?", message="Invalid email")//if the field contains email address consider using this annotation to enforce field validation
    @Size(max = 255)
    @Column(name = "Email")
    private String email;
    @Size(max = 255)
    @Column(name = "Telephone")
    private String telephone;
    @Size(max = 255)
    @Column(name = "Portable")
    private String portable;
    @Size(max = 255)
    @Column(name = "TypeInscription")
    private String typeInscription;
    // @Pattern(regexp="^\\(?(\\d{3})\\)?[- ]?(\\d{3})[- ]?(\\d{4})$", message="Invalid phone/fax format, should be as xxx-xxx-xxxx")//if the field contains phone or fax number consider using this annotation to enforce field validation
    @Size(max = 255)
    @Column(name = "Fax")
    private String fax;
    @Column(name = "DateModification")
    @Temporal(TemporalType.DATE)
    private Date dateModification;
    @Column(name = "DateCreation")
    @Temporal(TemporalType.DATE)
    private Date dateCreation;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "KeyTypeUser")
    private TypeUser typeUser;
    @Size(max = 1)
    @Column(name = "actif")
    private String actif;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "KeyEntreprise")
    private Entreprise entreprise;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "KeyCivilite")
    private Civilite civilite;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Login> loginCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<SourceInscription> sourceInscriptionCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<CorrespondanceImportation> CorrespondanceImportationCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Hotesse> hotesseCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Passage> passageCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Produit> produitCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Droit> droitCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<ReponseClient> reponseClientCollection;
    @OneToMany(mappedBy = "utilisateurSource",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<SourceInscription> PersonneUtilisateurSourceCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<AutreInformation> autreInformationCollection;
    @OneToMany(mappedBy = "personne",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<CrmLien> CrmLienCollection;
    @ManyToMany(cascade = CascadeType.ALL)
    private List<Session> sessionCollection;

    public Personne() {
    }

    public Personne(String keyClient) {
        this.keyClient = keyClient;
    }

    public String getKeyClient() {
        return keyClient;
    }

    public void setKeyClient(String keyClient) {
        this.keyClient = keyClient;
    }

    public String getNom() {
        return nom;
    }

    public void setNom(String nom) {
        this.nom = nom;
    }

    public String getPrenom() {
        return prenom;
    }

    public void setPrenom(String prenom) {
        this.prenom = prenom;
    }

    public String getTypeInscription() {
        return typeInscription;
    }

    public void setTypeInscription(String typeInscription) {
        this.typeInscription = typeInscription;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public String getTelephone() {
        return telephone;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public String getPortable() {
        return portable;
    }

    public void setPortable(String portable) {
        this.portable = portable;
    }

    public String getFax() {
        return fax;
    }

    public void setFax(String fax) {
        this.fax = fax;
    }

    public Date getDateModification() {
        return dateModification;
    }

    public void setDateModification(Date dateModification) {
        this.dateModification = dateModification;
    }

    public Date getDateCreation() {
        return dateCreation;
    }

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

    public String getActif() {
        return actif;
    }

    public void setActif(String actif) {
        this.actif = actif;
    }

    public TypeUser getTypeUser() {
        return typeUser;
    }

    public void setTypeUser(TypeUser typeUser) {
        this.typeUser = typeUser;
    }
    @XmlTransient
    public List<Login> getLoginCollection() {
        return loginCollection;
    }

    public void setLoginCollection(List<Login> loginCollection) {
        this.loginCollection = loginCollection;
    }
    @XmlTransient
    public List<CrmLien> getCrmLienCollection() {
        return CrmLienCollection;
    }

    public void setCrmLienCollection(List<CrmLien> CrmLienCollection) {
        this.CrmLienCollection = CrmLienCollection;
    }

    @XmlTransient
    public List<SourceInscription> getSourceInscriptionCollection() {
        return sourceInscriptionCollection;
    }

    public void setSourceInscriptionCollection(List<SourceInscription> sourceInscriptionCollection) {
        this.sourceInscriptionCollection = sourceInscriptionCollection;
    }

    public Entreprise getEntreprise() {
        return entreprise;
    }

    public void setEntreprise(Entreprise entreprise) {
        this.entreprise = entreprise;
    }
    @XmlTransient
    public List<CorrespondanceImportation> getCorrespondanceImportationCollection() {
        return CorrespondanceImportationCollection;
    }

    public void setCorrespondanceImportationCollection(List<CorrespondanceImportation> CorrespondanceImportationCollection) {
        this.CorrespondanceImportationCollection = CorrespondanceImportationCollection;
    }

    public Civilite getCivilite() {
        return civilite;
    }

    public void setCivilite(Civilite civilite) {
        this.civilite = civilite;
    }
    @XmlTransient
    public List<Hotesse> getHotesseCollection() {
        return hotesseCollection;
    }

    public void setHotesseCollection(List<Hotesse> hotesseCollection) {
        this.hotesseCollection = hotesseCollection;
    }
    @XmlTransient
    public List<Passage> getPassageCollection() {
        return passageCollection;
    }

    public void setPassageCollection(List<Passage> passageCollection) {
        this.passageCollection = passageCollection;
    }
    @XmlTransient
    public List<SourceInscription> getPersonneUtilisateurSourceCollection() {
        return PersonneUtilisateurSourceCollection;
    }

    public void setPersonneUtilisateurSourceCollection(List<SourceInscription> PersonneUtilisateurSourceCollection) {
        this.PersonneUtilisateurSourceCollection = PersonneUtilisateurSourceCollection;
    }

    @XmlTransient
    public List<Produit> getProduitCollection() {
        return produitCollection;
    }

    public void setProduitCollection(List<Produit> produitCollection) {
        this.produitCollection = produitCollection;
    }
    @XmlTransient
    public List<Droit> getDroitCollection() {
        return droitCollection;
    }

    public void setDroitCollection(List<Droit> droitCollection) {
        this.droitCollection = droitCollection;
    }
    @XmlTransient
    public List<ReponseClient> getReponseClientCollection() {
        return reponseClientCollection;
    }

    public void setReponseClientCollection(List<ReponseClient> reponseClientCollection) {
        this.reponseClientCollection = reponseClientCollection;
    }
    @XmlTransient
    public List<AutreInformation> getAutreInformationCollection() {
        return autreInformationCollection;
    }

    public void setAutreInformationCollection(List<AutreInformation> autreInformationCollection) {
        this.autreInformationCollection = autreInformationCollection;
    }
    @XmlTransient
     public List<Session> getSessionCollection() {
        return sessionCollection;
    }

    public void setSessionCollection(List<Session> sessionCollection) {
        this.sessionCollection = sessionCollection;
    }
    @Override
    public int hashCode() {
        int hash = 0;
        hash += (keyClient != null ? keyClient.hashCode() : 0);
        return hash;
    }
    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Personne)) {
            return false;
        }
        Personne other = (Personne) object;
        if ((this.keyClient == null && other.keyClient != null) || (this.keyClient != null && !this.keyClient.equals(other.keyClient))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "fr.ietevents.client.Entity.Personne[ keyClient=" + keyClient + " ]";
    }

}

session 实体:

@Entity
@Table(name = "Session")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "Session.findAll", query = "SELECT s FROM Session s"),
    @NamedQuery(name = "Session.findByKeyEdition", query = "SELECT s FROM Session s WHERE s.keySession = :keySession"),
    @NamedQuery(name = "Session.findByNom", query = "SELECT s FROM Session s WHERE s.nom = :nom")})
public class Session implements Serializable {

    private static final long serialVersionUID = 1L;
    @Id
    @Basic(optional = false)
    @NotNull
    @Column(name = "KeySession")
    private String keySession;
    @Size(max = 90)
    @Column(name = "Nom")
    private String nom;
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "KeyAdresse")
    private Adresse adresse ;
    @OneToMany(mappedBy = "session",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Passage> passageCollection;
    @OneToMany(mappedBy = "session",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Droit> droitCollection;
    @OneToMany(mappedBy = "session",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Question> questionCollection;
    @OneToMany(mappedBy = "session",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Css> cssCollection;
    @OneToMany(mappedBy = "session",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<Site> siteCollection;
     @OneToMany(mappedBy = "session",cascade = CascadeType.ALL,fetch = FetchType.EAGER)
    private List<CrmLien> crmLienCollection;
    @ManyToMany(mappedBy="sessionCollection",cascade = CascadeType.ALL)
    private List<Personne> personneCollection;

    public Session() {
    }
    public Session(String keySession) {
        this.keySession = keySession;
    }

    public String getKeySession() {
        return keySession;
    }

    public void setKeySession(String keyEdition) {
        this.keySession = keyEdition;
    }

    public String getNom() {
        return nom;
    }

    public void setNom(String nom) {
        this.nom = nom;
    }

    public Adresse getAdresse() {
        return adresse;
    }

    public void setAdresse(Adresse adresse) {
        this.adresse = adresse;
    }
    @XmlTransient
    public List<CrmLien> getCrmLienCollection() {
        return crmLienCollection;
    }

    public void setCrmLienCollection(List<CrmLien> crmLienCollection) {
        this.crmLienCollection = crmLienCollection;
    }

    @XmlTransient
    public List<Passage> getPassageCollection() {
        return passageCollection;
    }

    public void setPassageCollection(List<Passage> passageCollection) {
        this.passageCollection = passageCollection;
    }
    @XmlTransient
    public List<Droit> getDroitCollection() {
        return droitCollection;
    }

    public void setDroitCollection(List<Droit> droitCollection) {
        this.droitCollection = droitCollection;
    }
    @XmlTransient
    public List<Question> getQuestionCollection() {
        return questionCollection;
    }

    public void setQuestionCollection(List<Question> questionCollection) {
        this.questionCollection = questionCollection;
    }
    @XmlTransient
    public List<Css> getCssCollection() {
        return cssCollection;
    }

    public void setCssCollection(List<Css> CssCollection) {
        this.cssCollection = CssCollection;
    }
    @XmlTransient
    public List<Site> getSiteCollection() {
        return siteCollection;
    }

    public void setSiteCollection(List<Site> siteCollection) {
        this.siteCollection = siteCollection;
    }
    @XmlTransient
    public List<Personne> getPersonneCollection() {
        return personneCollection;
    }

    public void setPersonneCollection(List<Personne> personneCollection) {
        this.personneCollection = personneCollection;
    }
    @Override
    public int hashCode() {
        int hash = 0;
        hash += (keySession != null ? keySession.hashCode() : 0);
        return hash;
    }



    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Session)) {
            return false;
        }
        Session other = (Session) object;
        if ((this.keySession == null && other.keySession != null) || (this.keySession != null && !this.keySession.equals(other.keySession))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "fr.ietevents.client.Entity.Session[ keyEdition=" + keySession + " ]";
    }

}

我的 Collection session 是一个对象 session 列表。

public Long CountPersonne(Session  session,Pays pays){
      EntityManager em = getEntityManager();
      try{
          Query query = em.createNamedQuery("Personne.CountPersonne");
          query.setParameter("keySession",session.getKeySession());
        //  query.setParameter("keyPays",pays.getKeyPays());
         return (Long) query.getSingleResult();

      }catch(Exception e){
          System.out.println(e);
          return 0l;
      }finally{
             em.close();

        }
  }

错误消息:

javax.persistence.PersistenceException: Exception [EclipseLink-28019] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.EntityManagerSetupException
Exception Description: Deployment of PersistenceUnit [fr.ietevents_Client_war_1.0-SNAPSHOTPU] failed. Close all factories for this PersistenceUnit.
Internal Exception: Exception [EclipseLink-0] (Eclipse Persistence Services - 2.5.2.v20140319-9ad6abd): org.eclipse.persistence.exceptions.JPQLException
Exception Description: Problem compiling [SELECT COUNT(p) FROM Personne p WHERE p.sessionCollection.keySession = :keySession ]. 
[38, 68] The state field path 'p.sessionCollection.keySession' cannot be resolved to a valid type.
    org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.createDeployFailedPersistenceException(EntityManagerSetupImpl.java:820)
    org.eclipse.persistence.internal.jpa.EntityManagerSetupImpl.deploy(EntityManagerSetupImpl.java:760)
    org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getAbstractSession(EntityManagerFactoryDelegate.java:204)
    org.eclipse.persistence.internal.jpa.EntityManagerFactoryDelegate.getDatabaseSession(EntityManagerFactoryDelegate.java:182)
    org.eclipse.persistence.internal.jpa.EntityManagerFactoryImpl.getDatabaseSession(EntityManagerFactoryImpl.java:527)
    org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactoryImpl(PersistenceProvider.java:140)
    org.eclipse.persistence.jpa.PersistenceProvider.createEntityManagerFactory(PersistenceProvider.java:177)
    javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:79)
    javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:54)
    fr.ietevents.client.Facades.SessionFacade.getEntityManager(SessionFacade.java:27)
    fr.ietevents.client.Facades.AbstractFacade.find(AbstractFacade.java:96)
    fr.ietevents.client.MyResource.getIt(MyResource.java:395)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:497)
    org.glassfish.jersey.server.model.internal.ResourceMethodInvocationHandlerFactory$1.invoke(ResourceMethodInvocationHandlerFactory.java:81)
    org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher$1.run(AbstractJavaResourceMethodDispatcher.java:144)
    org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.invoke(AbstractJavaResourceMethodDispatcher.java:161)
    org.glassfish.jersey.server.model.internal.JavaResourceMethodDispatcherProvider$TypeOutInvoker.doDispatch(JavaResourceMethodDispatcherProvider.java:205)
    org.glassfish.jersey.server.model.internal.AbstractJavaResourceMethodDispatcher.dispatch(AbstractJavaResourceMethodDispatcher.java:99)
    org.glassfish.jersey.server.model.ResourceMethodInvoker.invoke(ResourceMethodInvoker.java:389)
    org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:347)
    org.glassfish.jersey.server.model.ResourceMethodInvoker.apply(ResourceMethodInvoker.java:102)
    org.glassfish.jersey.server.ServerRuntime$2.run(ServerRuntime.java:326)
    org.glassfish.jersey.internal.Errors$1.call(Errors.java:271)
    org.glassfish.jersey.internal.Errors$1.call(Errors.java:267)
    org.glassfish.jersey.internal.Errors.process(Errors.java:315)
    org.glassfish.jersey.internal.Errors.process(Errors.java:297)
    org.glassfish.jersey.internal.Errors.process(Errors.java:267)
    org.glassfish.jersey.process.internal.RequestScope.runInScope(RequestScope.java:317)
    org.glassfish.jersey.server.ServerRuntime.process(ServerRuntime.java:305)
    org.glassfish.jersey.server.ApplicationHandler.handle(ApplicationHandler.java:1154)
    org.glassfish.jersey.servlet.WebComponent.serviceImpl(WebComponent.java:471)
    org.glassfish.jersey.servlet.WebComponent.service(WebComponent.java:425)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:383)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:336)
    org.glassfish.jersey.servlet.ServletContainer.service(ServletContainer.java:223)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    org.netbeans.modules.web.monitor.server.MonitorFilter.doFilter(MonitorFilter.java:393)

最佳答案

您不能使用

p.sessionCollection.keySession

在 JPQL 中，因为那里有一个多值字段。您需要自己在查询中形成 JOIN，如下所示

SELECT COUNT(p) FROM Personne p JOIN p.sessionCollection sc WHERE sc.keySession = :keySession

关于java - USE JpaWhere 带有列表 := Key，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/34851281/

文章推荐： java - 如何从路径到树列出文件和文件夹？

文章推荐： php - 如何在PHP中动态创建对象数组

文章推荐： azure - Visual Studio Online、多个云项目、持续集成

Python 这段代码做了什么？列表=列表[列表!=值]
如标题所示，ans_list是一个答案列表，ans_index是一个数字(答案在词汇表中的索引，但与atm无关) 这里生成的 tree.anslist 是什么？ (例如，仅针对第一个)，忽略迭代。 f
MySQL 列表 IN 列表
我目前将用户的输入存储在逗号分隔的列表中，如下所示: Userid | Options 1 | 1,2,5 用户在一个数组形式中勾选一组选项，然后用逗号连接起来 1,2,5 然后 MySQ
MySQL 列表 IN 列表
我目前将用户的输入存储在逗号分隔的列表中，如下所示: Userid | Options 1 | 1,2,5 用户在一个数组形式中勾选一组选项，然后用逗号连接起来 1,2,5 然后 MySQ
list - 我怎样才能完全展平一个列表(列表(列表)......)
我想知道如何完全展平列表和包含它们的东西。除其他外，我想出了一个解决方案，它可以将具有多个元素的东西滑倒并将它们放回原处，或者在滑倒后将具有一个元素的东西拿走。这与 How do I “flatte
list - 我怎样才能完全展平一个列表(列表(列表)......)
我想知道如何完全展平列表和包含它们的东西。除其他外，我想出了一个解决方案，它可以将具有多个元素的东西滑倒并将它们放回原处，或者在滑倒后将带有一个元素的东西拿走。这与 How do I “flatte
java - 列表<列表<字符串>>到字符串[][]
这个问题已经有答案了: Convert nested list to 2d array (3 个回答) 已关闭 7 年前。 java中有没有快捷方式可以转换 List> 到 String[][] ？
java - 列表<列表<对象>>排序
我在排序时遇到问题 List> 。我创建了一个自定义比较器，在其中编写了对数据进行排序的代码。 public class CustomComparator implements Comparator
java - 列表数组列表转换
这个问题已经有答案了: 已关闭10 年前。 Possible Duplicate: Java Generics: Cannot cast List to List? 我只是想知道为什么下面的java代
c# - 列表<逗号分隔的字符串> => 列表<字符串>?
试图想出一个 LINQy 方法来做到这一点，但我什么也没想到。我有一个对象列表<>，其中包含一个属性，该属性是逗号分隔的字母代码列表: lst[0].codes = "AA,BB,DD" lst[1
python - 列表 += 元组与列表 = 列表 + 元组
假设我有这些任务: points = [] point = (1, 2) 我怎么会这样做: points += point 它工作得很好，并且给了我点 = [1, 2]。但是，如果我这样做: poin
scala - 将列表[任务[列表[A]]]转换为任务[列表[A]]
如何在 scala 中将 List[Task[List[Header]]] 类型转换为 Task[List[Header]]。我有一个方法返回 Task[List[Header]] 并多次调用 do
java - 如何在Java中获取二维列表的元素？例如，列表<列表<整数>>
如何在 Java 中查找二维列表的元素？我有一个参数为 List> 的函数我想知道如何找到这个列表的行和列。最佳答案如果你喜欢 List> obj 然后你就可以像这样访问 obj.get(cur
java - 列表<列表没有按预期工作
分配 List到 List工作正常。分配 List>到 List>不编译。代码 public class Main { public static void main(String[] a
java - 列表<可序列化> vs 列表
我正在用 Java 编写一个方法，该方法必须接收并迭代 Serializable 的 List。有什么区别: public void myMethod(List list) { } 和 public
java - 通知网格/列表/树内网格/列表/树的更改
我看到很多人想用 mvvm 更新网格/列表/树的一部分，但他们不想刷新整个列表。对于所有遇到此问题的人，我做了以下示例。希望这对你有用。最佳答案这是一个简单的例子。整个代码中最重要的是: Bi
C++ 列表到 Python 列表
我正在为现有的 C++ 库编写包装器，该库使用列表，其中 T 是自定义结构。我被建议使用 vector 而不是列表，但我试图避免修改库。为了更好地理解这个场景，我做了一个简单的应用程序，使用一个列表
java - 列表 VS 列表<基础>
List list List list 这两种声明有什么区别吗？谢谢，最佳答案是的。 List可以包含所有派生自 Base 的不同事物的混合物. List包含同质项(从某种意义上说，它们必须全部
Java 泛型 : List, 列表<对象>、列表
有人可以尽可能详细地解释以下类型之间的区别吗？ List List List 让我更具体一点。我什么时候想使用 // 1 public void CanYouGiveMeAnAnswer(List l
python - 是否有任何 python 模块可以计算(列表，列表)元组的频率？
我有一个元组列表，每个元组都是一对列表。所以我的数据看起来像: mylist = [(['foo', 'bar'], ['bar', 'bar']),(['bar', 'bar'],['bar', '
list - 给定一个 (a * b) 列表，返回一个 (a * b list) 列表
也许是一个时髦的标题，但我遇到了以下问题: 给定一个类型为 (a * b) list 的列表，我想创建一个类型为 (a * b list) list 的新列表。一个例子: 给定列表 let testL

行者123

个人简介

我是一名优秀的程序员,十分优秀！

作者热门文章

滴滴打车优惠券免费领取

全站热门文章

首页

博学

6Ren·AI

商城

java - USE JpaWhere 带有列表 := Key