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[英]Hibernate @OneToMany association creates duplicates when saving parent entity
[英]Hibernate: OneToMany Association not working Unknown entity error
嘗試創建一對多關聯時出現以下錯誤
Exception in thread "main" org.hibernate.MappingException: Unknown entity: org.hibernate.collection.internal.PersistentBag
這是運行創建關聯的代碼的地方
public void assignDoctorSpecialty(Doctor doctor, Specialty specialty) {
Session session = sessionFactory.openSession();
session.beginTransaction();
doctor.setSpecialty(specialty);
List<Doctor> doctors = specialty.getDoctors();
doctors.add(doctor);
session.save(doctors);
session.getTransaction().commit();
session.close();
}
這是我的醫生課
package edu.cs157b.hibernate;
import java.util.ArrayList;
import javax.persistence.*;
@Entity
@Table(name="DOCTOR_INFO")
@NamedQueries (
{
@NamedQuery(name = "Doctor.getAll", query = "from Doctor"),
@NamedQuery(name = "Doctor.findByName", query = "from Doctor where name = :name")
}
)
public class Doctor implements Person {
private int id;
private String name;
private Specialty specialty;
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column(unique=true)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@ManyToOne (fetch = FetchType.EAGER, cascade= CascadeType.PERSIST)
@JoinColumn(name="specialty_id")
public Specialty getSpecialty() {
return specialty;
}
public void setSpecialty(Specialty specialty) {
this.specialty = specialty;
}
}
這是我的專業課
package edu.cs157b.hibernate;
import java.util.ArrayList;
import javax.persistence.*;
import java.util.List;
@Entity
@Table(name="SPECIALTY_INFO")
@NamedQueries (
{
@NamedQuery(name = "Specialty.getAll", query = "from Specialty"),
@NamedQuery(name = "Specialty.findByName", query = "from Specialty where name = :name")
}
)
public class Specialty {
private List<Doctor> doctors = new ArrayList<Doctor>();
private int id;
private String name;
@Id
@GeneratedValue
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
@Column(unique=true)
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@OneToMany(mappedBy="specialty", targetEntity = Doctor.class,
fetch=FetchType.LAZY, cascade= CascadeType.PERSIST)
public List<Doctor> getDoctors() {
return doctors;
}
public void setDoctors(List<Doctor> doctors) {
this.doctors = doctors;
}
}
編輯
如果我直接保存Doctor
對象,而不是嘗試通過Cascade保存Specialty
Doctor列表間接保存它,則不會引發任何錯誤。 然而,當我進入我的數據庫, specialty_id
了的Doctor
表未設置。
據我所知,不可能使用save(..)
方法持久save(..)
對象集合。 嘗試以下代碼:
public void assignDoctorSpecialty(Doctor doctor, Specialty specialty) {
[...]
for (Doctor d : doctors) {
session.save(d);
}
session.getTransaction().commit();
session.close();
}
我想出了答案。 發生這種情況的原因是因為我嘗試save
一個已經保存在數據庫中的對象。 我要做的就是用session.save(doctor)
替換session.saveOrUpdate(doctor)
。
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