Manage JPA Entity with Set data structure - using add method - spring-boot

Question

I see examples where HashSet used in entity, and is treated like other data types. But I am looking to use "add" instead of set whole object
package com.baeldung.manytomany.model;
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
#Entity
#Table(name = "student")
public class Student {
#Id
#Column(name = "id")
private Long id;
#ManyToMany
#JoinTable(name = "course_like", joinColumns = #JoinColumn(name = "student_id"), inverseJoinColumns = #JoinColumn(name = "course_id"))
private Set<Course> likedCourses = new HashSet<>();
#OneToMany(mappedBy = "student")
private Set<CourseRating> ratings = new HashSet<>();
#OneToMany(mappedBy = "student")
private Set<CourseRegistration> registrations = new HashSet<>();
// additional properties
public Student() {
}
public Student(Long id) {
this.id = id;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public Set<Course> getLikedCourses() {
return likedCourses;
}
public void setLikedCourses(Set<Course> likedCourses) {
this.likedCourses = likedCourses;
}
public Set<CourseRating> getRatings() {
return ratings;
}
public void setRatings(Set<CourseRating> ratings) {
this.ratings = ratings;
}
public Set<CourseRegistration> getRegistrations() {
return registrations;
}
public void setRegistrations(Set<CourseRegistration> registrations) {
this.registrations = registrations;
}
#Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((id == null) ? 0 : id.hashCode());
return result;
}
#Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Student other = (Student) obj;
if (id == null) {
if (other.id != null)
return false;
} else if (!id.equals(other.id))
return false;
return true;
}
}
Is there a better approach than
public Set<CourseRating> getRatings() {
return ratings;
}
public void setRatings(Set<CourseRating> ratings) {
this.ratings = ratings;
}
I did try
public void addRatings(CourseRating rating) {
this.ratings.add(rating); }
but object is not persisting. I thought save of student should take care of saving rating. What am I missing ?

Answer 1

ok sorted
(1)
public void addRatings(CourseRating rating) {
this.ratings.add(rating); rating.setBlah(this);
}
(2) Updated Entity:
#OneToMany(cascade = CascadeType.ALL, mappedBy = "exam", orphanRemoval = true)
#OrderBy("id")
private Set<CourseRating> ratings = new HashSet<>();
Was using Embeddable, so was getting error - null id generated for:class ... so setting id from available objects
ratings.setId(new ThatKey(some1, some2));