Java org.hibernate.LazyInitializationException:无法初始化代理-在使用急切初始化时没有会话
我有hibernate映射: 前置词:Java org.hibernate.LazyInitializationException:无法初始化代理-在使用急切初始化时没有会话,java,hibernate,jpa,orm,Java,Hibernate,Jpa,Orm,我有hibernate映射: 前置词: @Entity @Table(name = "prepod") public class Prepod { private Long id; private String name; @Column public String getName() { return name; } public void setName(String name) { this.name =
@Entity
@Table(name = "prepod")
public class Prepod {
private Long id;
private String name;
@Column
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
List<Student> students = new ArrayList<Student>();
@ManyToMany(fetch=FetchType.EAGER)
public List<Student> getStudents() {
return students;
}
public void setStudents(List<Student> students) {
this.students = students;
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
public Long getId() {
return id;
}
public void setId(Long i) {
id = i;
}
}
@实体
@表(name=“prepd”)
公共类介词{
私人长id;
私有字符串名称;
@纵队
公共字符串getName(){
返回名称;
}
公共void集合名(字符串名){
this.name=名称;
}
List students=new ArrayList();
@ManyToMany(fetch=FetchType.EAGER)
公众学生名单{
留学生;
}
公立学校学生(名单学生){
这个。学生=学生;
}
@身份证
@GeneratedValue(策略=GenerationType.IDENTITY)
@列(name=“id”)
公共长getId(){
返回id;
}
公共无效设置ID(长i){
id=i;
}
}
学生:
@Entity
@Table(name = "Student")
public class Student {
private Long id;
private String name;
private Long age;
private List<Prepod> prepods = new ArrayList<Prepod>();
@ManyToMany(mappedBy = "students",fetch=FetchType.EAGER)
public List<Prepod> getPrepods() {
return prepods;
}
public void setPrepods(List<Prepod> prepods) {
this.prepods = prepods;
}
public Student() {
name = null;
}
public Student(Student s) {
name = s.getName();
}
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
public Long getId() {
return id;
}
@Column(name = "name")
public String getName() {
return name;
}
@Column(name = "age")
public Long getAge() {
return age;
}
public void setId(Long i) {
id = i;
}
public void setName(String s) {
name = s;
}
public void setAge(Long age) {
this.age = age;
}
}
@实体
@表(name=“Student”)
公立班学生{
私人长id;
私有字符串名称;
私人长寿;
private List preposd=new ArrayList();
@ManyToMany(mappedBy=“students”,fetch=FetchType.EAGER)
公共列表getPrepDS(){
返回介词;
}
公共void setprepDS(列表prepDS){
this.preposds=preposds;
}
公立学生(){
name=null;
}
公立学生{
name=s.getName();
}
@身份证
@GeneratedValue(策略=GenerationType.IDENTITY)
@列(name=“id”)
公共长getId(){
返回id;
}
@列(name=“name”)
公共字符串getName(){
返回名称;
}
@列(name=“age”)
公共长假{
回归年龄;
}
公共无效设置ID(长i){
id=i;
}
公共void集合名(字符串s){
name=s;
}
公共空间设置(长时间){
这个。年龄=年龄;
}
}
调用代码:
Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
Prepod prepod = (Prepod) session.load(Prepod.class, 1l);
Student student = (Student) session.load(Student.class, 1l);
session.getTransaction().commit();
session.flush();
session.close();
List<Student> students = new ArrayList<Student>();
students.add(student);
List<Prepod> prepods = new ArrayList<Prepod>();
prepods.add(prepod);
prepod.setStudents(students);//exception here
student.setPrepods(prepods);
....
会话会话=HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
prepd prepd=(prepd)session.load(prepd.class,1l);
学生=(学生)课时负荷(学生班级,1l);
session.getTransaction().commit();
session.flush();
session.close();
List students=new ArrayList();
学生。添加(学生);
List preposd=new ArrayList();
添加(prepd);
预备班学生(学生)//这里例外
student.setPrepods(prepods);
....
当我调用上面的代码时,我会看到下一个跟踪:
线程“main”org.hibernate.LazyInitializationException中的异常:
无法初始化代理-服务器上没有会话
org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:164)
在
org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:285)
在
org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:185)
在
logic.prepd\u$$\ uJavassist\u1.setStudents(prepd\u$$\ uJavassist\u1.java)
at logic.Main.Main(Main.java:38)
这个问题的原因是什么
我的对象的状态在最后两行中分离
如何修复它
更新
在收到Prabhakaran关于编辑代码的好建议后,我有一个问题:
若我更新了student-note,那个么它并没有添加到数据库的中间表中,而是添加了另一个行为,若我更新了prepod实体。发生这种情况是因为prepd是关系的所有者?prepd-prepd=null;
Prepod prepod = null;
Student student = null;
Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
prepod = (Prepod) session.load(Prepod.class, 1l);
student = (Student) session.load(Student.class, 1l);
session.getTransaction().commit();
session.flush();
session.close();
List<Student> students = new ArrayList<Student>();
students.add(student);
List<Prepod> prepods = new ArrayList<Prepod>();
prepods.add(prepod);
prepod.getStudents().addAll(students);//exception here
student.getPrepods().addAll(prepods);
Student=null;
Session Session=HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
prepd=(prepd)session.load(prepd.class,1l);
学生=(学生)课时负荷(学生班级,1l);
session.getTransaction().commit();
session.flush();
session.close();
List students=new ArrayList();
学生。添加(学生);
List preposd=new ArrayList();
添加(prepd);
prepod.getStudents().addAll(学生)//这里例外
student.getPrepDS().addAll(prepDS);
创建会话时出错:org.hibernate.AnnotationException:在关系的两侧非法使用mappedBy:logic.Student.prepDS异常在线程“main”java.lang.ExceptionInInitializeError位于logic.HibernateUtil.(HibernateUtil.java:51)位于logic.main.main(main.java:20)原因:org.hibernate.AnnotationException:在关系的两侧非法使用mappedBy:logic.Student.prepods