I cannot remove the association in Many To Many bidirectional hibernate - spring

Question

I can't delete the association in the courses_student table of course and student when trying to delete a course, even if I want to cascade delete it does not work for me since there is a foreign key in courses_student, I don't know what the problem is.
I have also tried to remove the association in the courses_student table doing a update.but nothing happened.
DAO
#Override
public boolean deleteCourse(int id) {
Session currentSession = entityManager.unwrap(Session.class);
Courses course = currentSession.load(Courses.class, id);
for(Student student : course.getEstudiantes()) {
course.removeStudent(student);
}
currentSession.delete(course);
if(course.getId() == null)
return true;
else
return false;
}
Courses entity
#Entity
#Table(name = "courses")
public class Courses {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="id")
private Integer id;
#Column
private String nombre;
#Column
private String descripcion;
#ManyToMany(mappedBy = "courses")
private Set<Student> Estudiantes = new HashSet<Student>();
public Courses() {
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getNombre() {
return nombre;
}
public void setNombre(String nombre) {
this.nombre = nombre;
}
public String getDescripcion() {
return descripcion;
}
public void setDescripcion(String descripcion) {
this.descripcion = descripcion;
}
public Set<Student> getEstudiantes() {
return Estudiantes;
}
public void setEstudiantes(Set<Student> estudiantes) {
Estudiantes = estudiantes;
}
public void removeStudent(Student student) {
this.Estudiantes.remove(student);
student.getCourses().remove(this);
}
}
Student entity
#Entity
#Table(name = "students")
public class Student {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name="id")
private Integer id;
#Column
private String nombre;
#Column
private String apellido;
#Column
private String dni;
#ManyToMany(fetch=FetchType.LAZY,
cascade= {CascadeType.PERSIST, CascadeType.MERGE,
CascadeType.DETACH, CascadeType.REFRESH})
#JoinTable(
name="courses_students",
joinColumns=#JoinColumn(name="id_student"),
inverseJoinColumns=#JoinColumn(name="id_course")
)
private Set<Courses> courses = new HashSet<Courses>();
public Student() {
}
public Student(String nombre, String apellido, String dni) {
this.nombre = nombre;
this.apellido = apellido;
this.dni = dni;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getNombre() {
return nombre;
}
public void setNombre(String nombre) {
this.nombre = nombre;
}
public String getApellido() {
return apellido;
}
public void setApellido(String apellido) {
this.apellido = apellido;
}
public String getDni() {
return dni;
}
public void setDni(String dni) {
this.dni = dni;
}
public Set<Courses> getCourses() {
return courses;
}
public void setCourses(Set<Courses> courses) {
this.courses = courses;
}
}
EDIT:
apparently it works for me, trying to update since owner side.
#Override
public boolean deleteCourse(int id) {
Session currentSession = entityManager.unwrap(Session.class);
Courses course = currentSession.load(Courses.class, id);
for(Student student : course.getEstudiantes()) {
student.removeCourse(course);
}
currentSession.update(course);
if(course.getId() == null)
return true;
else
return false;
}

Answer 1

It seems to me that you are missing a cascade configuration of your #ManyToMany annotation on Courses which is actually the one you are updating / deleting. Try the following:
#ManyToMany(mappedBy = "courses", cascade = {CascadeType.PERSIST, CascadeType.MERGE})
private Set<Student> Estudiantes = new HashSet<Student>();
Also, given that you have a bi-directional relationship, you should also remove the Course from each Student courses property.