Java中命名查询的问题

Question

我遇到问题。我使用JPA制作了一个动态Web项目，名为查询和一个Web Servlet。下面是该项目的组织：

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这里是类：

Auto.java：

package it.ecipar.model; 

import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.GenerationType; 
import javax.persistence.Id; 

@Entity 
public class Auto { 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private Integer id; 

    private String marca, modello; 

    public Integer getId() { 
     return id; 
    } 

    public void setId(Integer id) { 
     this.id = id; 
    } 

    public String getMarca() { 
     return marca; 
    } 

    public void setMarca(String marca) { 
     this.marca = marca; 
    } 

    public String getModello() { 
     return modello; 
    } 

    public void setModello(String modello) { 
     this.modello = modello; 
    } 

} 

Hobby.java：

package it.ecipar.model; 

import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.GenerationType; 
import javax.persistence.Id; 

@Entity 
public class Hobby { 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private Integer id; 

    private String nome; 

    public Integer getId() { 
     return id; 
    } 

    public void setId(Integer id) { 
     this.id = id; 
    } 

    public String getNome() { 
     return nome; 
    } 

    public void setNome(String nome) { 
     this.nome = nome; 
    } 

} 

Luogo.java：

package it.ecipar.model; 

import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.GenerationType; 
import javax.persistence.Id; 

@Entity 
public class Luogo { 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private Integer id; 

    private String nome; 

    public Integer getId() { 
     return id; 
    } 

    public void setId(Integer id) { 
     this.id = id; 
    } 

    public String getNome() { 
     return nome; 
    } 

    public void setNome(String nome) { 
     this.nome = nome; 
    } 

} 

Persona.java：

package it.ecipar.model; 

import java.util.Date; 
import java.util.List; 

import javax.persistence.Entity; 
import javax.persistence.GeneratedValue; 
import javax.persistence.GenerationType; 
import javax.persistence.Id; 
import javax.persistence.ManyToMany; 
import javax.persistence.ManyToOne; 
import javax.persistence.NamedQueries; 
import javax.persistence.NamedQuery; 
import javax.persistence.OneToMany; 


@NamedQueries({ 
    @NamedQuery(name="persona.lista", query="SELECT o from it.ecipar.model.Persona o ORDER by p.cognome, p.nome") 
}) 

@Entity 
public class Persona { 
    @Id 
    @GeneratedValue(strategy = GenerationType.AUTO) 
    private Integer id; 

    private String nome, cognome; 

    private Date dataDiNascita; 

    @OneToMany 
    private List<Auto> auto; 

    @ManyToMany 
    private List<Hobby> hobby; 

    @ManyToOne 
    private Luogo luogoDiNascita; 

    public Integer getId() { 
     return id; 
    } 

    public void setId(Integer id) { 
     this.id = id; 
    } 

    public String getNome() { 
     return nome; 
    } 

    public void setNome(String nome) { 
     this.nome = nome; 
    } 

    public String getCognome() { 
     return cognome; 
    } 

    public void setCognome(String cognome) { 
     this.cognome = cognome; 
    } 

    public List<Auto> getAuto() { 
     return auto; 
    } 

    public void setAuto(List<Auto> auto) { 
     this.auto = auto; 
    } 

    public List<Hobby> getHobby() { 
     return hobby; 
    } 

    public void setHobby(List<Hobby> hobby) { 
     this.hobby = hobby; 
    } 

    public Luogo getLuogoDiNascita() { 
     return luogoDiNascita; 
    } 

    public void setLuogoDiNascita(Luogo luogoDiNascita) { 
     this.luogoDiNascita = luogoDiNascita; 
    } 

    public Date getDataDiNascita() { 
     return dataDiNascita; 
    } 

    public void setDataDiNascita(Date dataDiNascita) { 
     this.dataDiNascita = dataDiNascita; 
    } 

} 

JPAUtil.java：

package it.ecipar.common; 

import java.util.HashMap; 
import java.util.List; 
import java.util.Set; 

import javax.persistence.EntityManager; 
import javax.persistence.EntityManagerFactory; 
import javax.persistence.Persistence; 
import javax.persistence.Query; 

public class JPAUtil { 

    private static EntityManagerFactory emf; 
    private EntityManager em; 

    public JPAUtil() { 
     if (emf == null) { 
      emf = Persistence.createEntityManagerFactory("MyProject"); 
     } 
     em = emf.createEntityManager(); 
    } 

    public Object insert(Object o) { 
     em.getTransaction().begin(); 
     em.persist(o); 
     em.getTransaction().commit(); 

     return o; 
    } 

    public Object update(Object o) { 
     em.getTransaction().begin(); 
     Object res = em.merge(o); 
     em.getTransaction().commit(); 

     return res; 
    } 

    public void delete(Object o) { 
     em.getTransaction().begin(); 
     em.remove(em.contains(o) ? o : em.merge(o)); 
     em.getTransaction().commit(); 
    } 

    public Object load(Class<?> c, Integer id) { 
     return em.find(c, id); 
    } 

    public List<?> runNamedQuery(String name, HashMap<String, Object> params) { 
     Query query = em.createNamedQuery(name); 
     if (params != null) { 
      Set<String> keys = params.keySet(); 
      for (String k : keys) { 
       query.setParameter(k, params.get(k)); 
      } 
     } 

     return query.getResultList(); 
    } 

    public Query createQuery(String q) { 
     return em.createQuery(q); 
    } 

    public void close() { 
     em.close(); 
    } 

    public void closeFactory() { 
     emf.close(); 
    } 
} 

Demo.java：

package it.ecipar.common; 

import java.util.ArrayList; 
import java.util.Calendar; 
import java.util.GregorianCalendar; 
import java.util.List; 

import it.ecipar.model.Auto; 
import it.ecipar.model.Hobby; 
import it.ecipar.model.Luogo; 
import it.ecipar.model.Persona; 

public class Demo { 

    public static void main(String[] args) { 
     JPAUtil u = new JPAUtil(); 

     for(int i = 0; i < 10; i++) { 
      save(u, i, i + 1); 
     } 

     u.close(); 
     u.closeFactory(); 
    } 

    public static void save(JPAUtil u, int i, int numAuto) { 

     Luogo l = new Luogo(); 
     l.setNome("nome luogo " + i); 
     u.insert(l); 

     List<Hobby> listaHobby = new ArrayList<>(); 
     Hobby h = new Hobby(); 
     h.setNome("nome hobby " + i); 
     u.insert(h); 
     listaHobby.add(h); 

     List<Auto> listaAuto = new ArrayList<>(); 
     for (int j = i; j < i + numAuto; j++) { 
      Auto a = new Auto(); 
      a.setMarca("marca " + j); 
      a.setModello("modello " + j); 

      u.insert(a); 

      listaAuto.add(a); 
     } 

     Calendar cal = GregorianCalendar.getInstance(); 
     cal.add(Calendar.YEAR, -20 * i); 

     Persona p = new Persona(); 
     p.setNome("nome " + i); 
     p.setCognome("cognome " + i); 
     p.setDataDiNascita(cal.getTime()); 
     p.setHobby(listaHobby); 
     p.setLuogoDiNascita(l); 
     p.setAuto(listaAuto); 

     u.insert(p); 
    } 
} 

下面是persistence.xml文件：

<persistence xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence 
      http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd" 
      version="2.1"> 

    <persistence-unit name="MyProject" transaction-type="RESOURCE_LOCAL"> 
    <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider> 

     <class>it.ecipar.model.Auto</class> 
     <class>it.ecipar.model.Hobby</class> 
     <class>it.ecipar.model.Luogo</class> 
     <class>it.ecipar.model.Persona</class> 
     <properties> 
     <property name="hibernate.connection.driver_class" value="org.postgresql.Driver" /> 
      <property name="hibernate.connection.url" value="jdbc:postgresql://localhost:5432/persone"/> 
      <property name="hibernate.connection.username" value="postgres" /> 
      <property name="hibernate.connection.password" value="postgres" /> 
      <property name="hibernate.dialect" value="org.hibernate.dialect.PostgreSQLDialect"/> 
      <property name="hibernate.show_sql" value="true" /> <!-- Show SQL in console --> 
      <property name="hibernate.format_sql" value="true" /> 
    </properties> 
    </persistence-unit> 
</persistence> 

这里是PersonaServlet.java：

package it.ecipar.web; 

import java.io.IOException; 
import java.io.PrintWriter; 
import java.util.List; 

import javax.servlet.ServletException; 
import javax.servlet.annotation.WebServlet; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 

import flexjson.JSONSerializer; 
import it.ecipar.common.JPAUtil; 
import it.ecipar.model.Persona; 

@SuppressWarnings("serial") 
@WebServlet(urlPatterns = { "/persone" }) 
public class PersonaServlet extends HttpServlet { 



    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 

     String id = req.getParameter("id"); 
     String json = null; 

     if (id == null) { 

      System.out.println("Ciao"); 
      @SuppressWarnings("unchecked") 
      List<Persona> list = (List<Persona>) new JPAUtil().runNamedQuery("personalista",null); 
      JSONSerializer js = new JSONSerializer(); 
      json = js.include("auto").include("hobby").serialize(list); 
     } else { 
      Persona p = (Persona) new JPAUtil().load(Persona.class, Integer.valueOf(id)); 
      JSONSerializer js = new JSONSerializer(); 
      json = js.include("auto").include("hobby").serialize(p); 
     } 

     resp.setContentType("application/json"); 

     PrintWriter w = resp.getWriter(); 
     w.print(json); 
     w.flush(); 
    } 
} 

当我运行它，它给我后继错误：

Exception in thread "main" javax.persistence.PersistenceException: Unable to build entity manager factory 
    at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:83) 
    at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:54) 
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:55) 
    at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:39) 
    at it.ecipar.common.JPAUtil.<init>(JPAUtil.java:19) 
    at it.ecipar.common.Demo.main(Demo.java:16) 
Caused by: org.hibernate.HibernateException: Errors in named queries: persona.lista 
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:545) 
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1857) 
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:850) 
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:843) 
    at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:398) 
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:842) 
    at org.hibernate.jpa.HibernatePersistenceProvider.createEntityManagerFactory(HibernatePersistenceProvider.java:75) 
    ... 5 more 

任何人都可以帮助我吗？谢谢。

Answer 1

您的查询

@NamedQuery(name="persona.lista", query="SELECT o from it.ecipar.model.Persona o ORDER by p.cognome, p.nome") 

中有一个错误。您有Persona o，但按p.cognome...订购。您需要使用相同的表格参考：

@NamedQuery(name="persona.lista", query="SELECT o from it.ecipar.model.Persona o ORDER by o.cognome, o.nome")