Java 在Hibernate 4中，内部联接用于子对象，同时访问；“每个子类一个表”；_Java_Sql_Hibernate_Join

Java 在Hibernate 4中，内部联接用于子对象，同时访问；“每个子类一个表”；

java sql hibernate join

Java 在Hibernate 4中，内部联接用于子对象，同时访问；“每个子类一个表”；,java,sql,hibernate,join,Java,Sql,Hibernate,Join,在Hibernate4中，当访问“每个子类一个表”的对象时，内部联接用于子对象 [编辑：这是Hibernate 4.3.5中的一个bug，将在4.3.6中修复。] 我有以下课程教授-基础班 ContractProfessor-从Professor派生的类全职教授-由教授派生的课程全职教授包含一个系的强制性目标。[在SQL中不为空] 教室包含Professor的对象，该对象可以为空当我询问教室时，我得到了错误。当我看到这个查询时，它正在与部门进行内部联接。如果它正在检索的教室是Contra

在Hibernate4中，当访问“每个子类一个表”的对象时，内部联接用于子对象

[编辑：这是Hibernate 4.3.5中的一个bug，将在4.3.6中修复。]

我有以下课程

教授-基础班

ContractProfessor-从Professor派生的类

全职教授-由教授派生的课程

全职教授包含一个系的强制性目标。[在SQL中不为空]

教室包含Professor的对象，该对象可以为空

当我询问教室时，我得到了错误。当我看到这个查询时，它正在与部门进行内部联接。如果它正在检索的教室是ContractProfessor，那么它将没有Department，并且内部连接失败，它将抛出异常

因为Professor对象可以为null，所以它应该始终对所有连接使用left join。但是，这是全职教授和系主任之间的内在联系。因此，当我试图检索教室对象时，会出现异常

这在Hibernate3中运行良好。但是，当我使用Hibernate4.3.5-Final时，我会出错

在不更改DB模式的情况下，我应该如何修复此问题

下面是相同的代码和sql

在Hibernate 4.3.5-Final中生成的查询

 select
     professor0_.id as id1_6_0_,
     professor0_.name as name2_6_0_,
     professor0_1_.hourlyRate as hourlyRa1_2_0_,
     professor0_2_.DepartmentId as Departme3_4_0_,
     professor0_2_.salary as salary1_4_0_,
     case
         when professor0_1_.id is not null then 1
         when professor0_2_.id is not null then 2
         when professor0_.id is not null then 0
     end as clazz_0_,
     department1_.id as id1_3_1_,
     department1_.name as name2_3_1_
 from
     Professor professor0_
 left outer join
     ContractProfessor professor0_1_
         on professor0_.id=professor0_1_.id
 left outer join
     FulltimeProfessor professor0_2_
         on professor0_.id=professor0_2_.id
 inner join
     Department department1_
         on professor0_2_.DepartmentId=department1_.id
 where
     professor0_.id=?

在Hibernate3中生成查询

 select
     professor0_.id as id2_1_,
     professor0_.name as name2_1_,
     professor0_1_.hourlyRate as hourlyRate3_1_,
     professor0_2_.DepartmentId as Departme3_8_1_,
     professor0_2_.salary as salary8_1_,
     case
         when professor0_1_.id is not null then 1
         when professor0_2_.id is not null then 2
         when professor0_.id is not null then 0
     end as clazz_1_,
     department1_.id as id1_0_,
     department1_.name as name1_0_
 from
     Professor professor0_
 left outer join
     ContractProfessor professor0_1_
         on professor0_.id=professor0_1_.id
 left outer join
     FulltimeProfessor professor0_2_
         on professor0_.id=professor0_2_.id
 left outer join
     Department department1_
         on professor0_2_.DepartmentId=department1_.id
 where
     professor0_.id=?

java教授

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;

@Entity
@Table(name = "Professor")
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class Professor {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private int id;

  private String name;

  public int getId() {
    return id;
  }

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

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public String toString() {
    return "Professor id: " + getId() + " name: " + getName();
  }
}

import javax.persistence.Entity;
import javax.persistence.Table;

@Entity
@Table(name="ContractProfessor")
public class ContractProfessor extends Professor {
    private long hourlyRate = 1;

    public long getHourlyRate() {
        return hourlyRate;
    }

    public void setHourlyRate(long hourlyRate) {
        this.hourlyRate = hourlyRate;
    }

    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

@Entity
@Table(name="FulltimeProfessor")
public class FulltimeProfessor extends Professor {
    private long salary = 1;

    @ManyToOne(fetch = FetchType.EAGER)
    @Fetch(FetchMode.JOIN)
    @JoinColumn(name = "DepartmentId", nullable = false)
    private Department department;

    public Department getDepartment()
    {
        return department;
    }

    public void setDepartment(Department department)
    {
        this.department = department;
    }

    public long getSalary() {
        return salary;
    }

    public void setSalary(long salary) {
        this.salary = salary;
    }

    public String toString() {
        return "FullTimeProfessor id: " + getId() + " name: " + getName();
    }
}

java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;

@Entity
@Table(name = "Professor")
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class Professor {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private int id;

  private String name;

  public int getId() {
    return id;
  }

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

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public String toString() {
    return "Professor id: " + getId() + " name: " + getName();
  }
}

import javax.persistence.Entity;
import javax.persistence.Table;

@Entity
@Table(name="ContractProfessor")
public class ContractProfessor extends Professor {
    private long hourlyRate = 1;

    public long getHourlyRate() {
        return hourlyRate;
    }

    public void setHourlyRate(long hourlyRate) {
        this.hourlyRate = hourlyRate;
    }

    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

@Entity
@Table(name="FulltimeProfessor")
public class FulltimeProfessor extends Professor {
    private long salary = 1;

    @ManyToOne(fetch = FetchType.EAGER)
    @Fetch(FetchMode.JOIN)
    @JoinColumn(name = "DepartmentId", nullable = false)
    private Department department;

    public Department getDepartment()
    {
        return department;
    }

    public void setDepartment(Department department)
    {
        this.department = department;
    }

    public long getSalary() {
        return salary;
    }

    public void setSalary(long salary) {
        this.salary = salary;
    }

    public String toString() {
        return "FullTimeProfessor id: " + getId() + " name: " + getName();
    }
}

FulltimeProfessor.java

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.InheritanceType;
import javax.persistence.Table;

@Entity
@Table(name = "Professor")
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class Professor {
  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private int id;

  private String name;

  public int getId() {
    return id;
  }

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

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }

  public String toString() {
    return "Professor id: " + getId() + " name: " + getName();
  }
}

import javax.persistence.Entity;
import javax.persistence.Table;

@Entity
@Table(name="ContractProfessor")
public class ContractProfessor extends Professor {
    private long hourlyRate = 1;

    public long getHourlyRate() {
        return hourlyRate;
    }

    public void setHourlyRate(long hourlyRate) {
        this.hourlyRate = hourlyRate;
    }

    public String toString() {
        return "ContractProfessor id: " + getId() + " name: " + getName();
    }
}

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

@Entity
@Table(name="FulltimeProfessor")
public class FulltimeProfessor extends Professor {
    private long salary = 1;

    @ManyToOne(fetch = FetchType.EAGER)
    @Fetch(FetchMode.JOIN)
    @JoinColumn(name = "DepartmentId", nullable = false)
    private Department department;

    public Department getDepartment()
    {
        return department;
    }

    public void setDepartment(Department department)
    {
        this.department = department;
    }

    public long getSalary() {
        return salary;
    }

    public void setSalary(long salary) {
        this.salary = salary;
    }

    public String toString() {
        return "FullTimeProfessor id: " + getId() + " name: " + getName();
    }
}

Department.java

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

@Entity
@Table(name = "Department")
public class Department
{
      private long id;

      private String name;

      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      public long getId() {
        return id;
      }

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

      public String getName() {
        return name;
      }

      public void setName(String name) {
        this.name = name;
      }

      public String toString() {
        return "Department id: " + getId() + " name: " + getName();
      }
}

java

import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.Fetch;
import org.hibernate.annotations.FetchMode;

@Entity
@Table(name = "Classroom")
public class Classroom
{
      private long id;

      private String name;

      private Professor professor;

      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      public long getId() {
        return id;
      }

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

      public String getName() {
        return name;
      }

      public void setName(String name) {
        this.name = name;
      }

      public String toString() {
        return "Classroom id: " + getId() + " name: " + getName();
      }

      @ManyToOne(fetch = FetchType.EAGER)
      @Fetch(FetchMode.JOIN)
      @JoinColumn(name = "ProfessorId", nullable = true)
      public Professor getProfessor()
      {
        return professor;
      }

      public void setProfessor(Professor professor)
      {
        this.professor = professor;
      }
}

InnerJoinMain.java

import java.util.Collection;
import java.util.Date;

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

public class InnerJoinMain
{
      public static void main(String[] args) throws Exception 
      {
            EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
            EntityManager em = emf.createEntityManager();

            em.getTransaction().begin();
            int time = (int)((new Date().getTime() / 1000) % 10000);
            System.out.println(time);

            ContractProfessor cprof = new ContractProfessor();
            cprof.setName("CProf" + time);
            cprof.setHourlyRate(time);
            em.persist(cprof);

            Department dept = new Department();
            dept.setName("Dept" + time);
            em.persist(dept);

            FulltimeProfessor fprof = new FulltimeProfessor();
            fprof.setName("Fprof" + time);
            fprof.setDepartment(dept);
            fprof.setSalary(time + 10);
            em.persist(fprof);

            Classroom cls = new Classroom();
            cls.setName("Classroom" + time);
            cls.setProfessor(cprof);
            em.persist(cls);

            cls = new Classroom();
            cls.setName("Classroom" + (time+1));
            cls.setProfessor(fprof);
            em.persist(cls);

            cls = new Classroom();
            cls.setName("Classroom" + (time+2));
            em.persist(cls);

            em.getTransaction().commit();

            em.getTransaction().begin();

            Query query = em.createQuery("SELECT c FROM Classroom c");
            for(Classroom c : (Collection<Classroom>) query.getResultList()) {
                System.out.println(c);
            }

            em.getTransaction().commit();
            em.close();
            emf.close();
      }
}

import java.util.Collection；
导入java.util.Date；
导入javax.persistence.EntityManager；
导入javax.persistence.EntityManagerFactory；
导入javax.persistence.persistence；
导入javax.persistence.Query；
公共类
{
公共静态void main（字符串[]args）引发异常
{
EntityManagerFactory emf=Persistence.createEntityManagerFactory（“ProfessorService”）；
EntityManager em=emf.createEntityManager（）；
em.getTransaction（）.begin（）；
int time=（int）（（new Date（）.getTime（）/1000）%10000）；
系统输出打印LN（时间）；
ContractProfessor cprof=新ContractProfessor（）；
cprof.setName（“cprof”+时间）；
cprof.setHourlyRate（时间）；
em.persist（cprof）；
部门=新部门（）；
部门名称（“部门”+时间）；
em.persist（dept）；
全职教授fprof=新的全职教授（）；
fprof.setName（“fprof”+时间）；
财务部（部门）；
fprof.设置量程（时间+10）；
em.persist（fprof）；
教室cls=新教室（）；
cls.setName（“教室”+时间）；
大学教授（cprof）；
em.persist（cls）；
cls=新教室（）；
cls.setName（“教室”+（时间+1））；
教授（fprof）；
em.persist（cls）；
cls=新教室（）；
cls.setName（“教室”+（时间+2））；
em.persist（cls）；
em.getTransaction（）.commit（）；
em.getTransaction（）.begin（）；
Query Query=em.createQuery（“从教室c中选择c”）；
for（课堂c:（集合）query.getResultList（））{
系统输出打印ln（c）；
}
em.getTransaction（）.commit（）；
em.close（）；
emf.close（）；
}
}