休眠-更新操作：

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

    private String id;
    private String firstName;
    private String lastName;
    private Set<Grade> grades = new HashSet<Grade>();

public void addGrade(Grade grade){
        grades.add(grade);
    }
    //rest of Getters and setters omitted

    public void removeGrade(Grade grade){
    grades.remove(grade);
    }
@OneToMany(cascade = CascadeType.ALL,fetch=FetchType.LAZY,orphanRemoval=true)
    @JoinColumn(name=\"s_id\")
    public Set<Grade> getGrades() {
        return grades;
    }

@Entity
@Table(name=\"Grade\")
public class Grade {
//all omitted
}

String id = \"xyz\";
Session session = sessionFactory.getCurrentSession();
    Student student = (Student)session.load(Student.class,id);
        student.removeGrade(grade);
        session.update(student);

Hibernate: select student0_.id as id0_0_, student0_.FirstName as FirstName0_0_, student0_.LASTNAME as LASTNAME0_0_ from Student student0_ where student0_.id=?
Hibernate: select grades0_.s_id as s4_0_1_, grades0_.id as id1_, grades0_.id as id1_0_, grades0_.FirstQuestion as FirstQue2_1_0_, grades0_.TotalGrade as TotalGrade1_0_ from Grade grades0_ where grades0_.s_id=?
Hibernate: update Grade set s_id=null where s_id=? and id=?
Hibernate: delete from Grade where id=?

update Grade set s_id=null where s_id=? and id=?