Исключение в потоке «основной» org.hibernate.Exception.ConstraintViolationException: не удалось выполнить оператор ⇐ JAVA

[Anonymous]

В чем причина моей ошибки?
У меня есть сущности. Их отношение - многие ко многим.

препод:

Код: Выделить всё

@Entity(name = "prepod")
public class Prepod {

private Long id;

List students = new ArrayList();

@ManyToMany
public List getStudents() {
return students;
}

public void setStudents(List students) {
this.students = students;
}

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
public Long getId() {
return id;
}

public void setId(Long i) {
id = i;
}
}

ученик:

Код: Выделить всё

@Entity
@Table(name="Student")
public class Student {

private Long id;
private String name;
private Long age;
private List
 prepods = new ArrayList();

@ManyToMany(mappedBy="students")
public List getPrepods() {
return prepods;
}

public void setPrepods(List 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;
}
}

Код вызова:

Код: Выделить всё

public static void main(String[] args){
Prepod prepod = new Prepod();
prepod.setId(1l);
Student student = new Student();
student.setId(1l);
student.setName("qweqwe");
prepod.getStudents().add(student);
student.getPrepods().add(prepod);

Session session = HibernateUtil.getSessionFactory().openSession();
session.beginTransaction();
session.save(prepod);
session.save(student);
session.getTransaction().commit();
}

текст исключения:

Код: Выделить всё

Hibernate: insert into prepod default values
Exception in thread "main" org.hibernate.exception.ConstraintViolationException: could not execute statement
at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:129)
at org.hibernate.exception.internal.StandardSQLExceptionConverter.convert(StandardSQLExceptionConverter.java:49)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:125)
at org.hibernate.engine.jdbc.spi.SqlExceptionHelper.convert(SqlExceptionHelper.java:110)
at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:136)
at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:96)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:58)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2975)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:3487)
at org.hibernate.action.internal.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:81)
at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:364)
at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:205)
at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:185)
at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:169)
at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:321)
at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:286)
at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:192)
at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:125)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:206)
at org.hibernate.event.internal.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:55)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:191)
at org.hibernate.event.internal.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:49)
at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
at org.hibernate.internal.SessionImpl.fireSave(SessionImpl.java:764)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:756)
at org.hibernate.internal.SessionImpl.save(SessionImpl.java:752)
at logic.Main.main(Main.java:17)

Таблицы создаются в базах данных, но данные не вставляются в мои таблицы.

Можете ли вы объяснить мне, в чем причина?

Как это исправить?

ОБНОВИТЬ

сгенерированная схема:




Подробнее здесь: https://stackoverflow.com/questions/187 ... nexception