No adding entity in a manytoone relationship using spring boot and jpa - mysql

Question

I'm new in spring boot, I'm looking for help with this problem: I have two entities connected by a ManytoOne relationship. The entities are course and professor.
The professor Entity:
#Entity
#Table(name = "professor")
public class Professor implements Serializable {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Long idProfessor;
private String name;
private String lastName;
private String phone;
private String mail;
#Fetch(FetchMode.JOIN)
#OneToMany(mappedBy = "professor", cascade= CascadeType.ALL)
private List<Course> courses;
public Professor() {
}
public Long getIdProfessor() {
return idProfessor;
}
public void setIdProfessor(Long idProfessor) {
this.idProfessor = idProfessor;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getPhone() {
return phone;
}
public void setPhone(String phone) {
this.phone = phone;
}
public String getMail() {
return mail;
}
public void setMail(String mail) {
this.mail = mail;
}
}
The Course Entity:
#Entity
#Table(name = "course")
public class Course implements Serializable {
#Id
#GeneratedValue(strategy=GenerationType.IDENTITY)
private Long idCourse;
private String title;
private String description;
#ManyToOne
#JoinColumn(name="professor_id")
private Professor professor;
#ManyToMany(mappedBy = "courses")
private List<Student> students;
public Course() {}
public Long getIdCourse() {
return idCourse;
}
public void setIdCourse(Long idCourse) {
this.idCourse = idCourse;
}
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
}
I also created a rest controller to create Course and I defined POST endpoint like this:
#PostMapping(value="/create")
public Course createCourse(#RequestBody Course course) {
return courseRepo.save(course);
}
When I add a new course in postman, the course is added but it is not assigned to the corresponding professor (an existing professor in the database), "idProfessor" is always assigned to NULL. Here is an example of POST API execution in postman and the result in MySQL.
postman
mysql
Any suggestions?