java - hibernate：已经存在一个班级，已经存在多个学生，建立多个学生与班级之间的关系

hibernate问题
已经存在一个班级，已经存在多个学生，建立多个学生与班级之间的关系
这个怎么实现，请教各位大神
这是一个已经存在一个班级，已经存在一个学生，建立该班级与该学生之间的关系
@Test

public void testR_1() {
    Session session = sessionFactory.openSession();
    Transaction transaction = session.beginTransaction();
    Classes classes1 = (Classes) session.get(Classes.class, 1L);
    Student student = (Student) session.get(Student.class, 6L);
    classes1.getStudents().add(student);
    transaction.commit();
    session.close();
}

public class Classes implements Serializable {

private Long cid;
private String cname;
private String description;
private Set students;

public Long getCid() {
    return cid;
}

public void setCid(Long cid) {
    this.cid = cid;
}

public String getCname() {
    return cname;
}

public void setCname(String cname) {
    this.cname = cname;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public Set getStudents() {
    return students;
}

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

}

xml配置



    
        
            
        
        
        
        
        
        
            
            
                
            
            
        
    

我是这么做的

11、已经存在一个班级，已经存在多个学生，建立多个学生与班级之间的关系
     */
    @Test
    public void testR_2() {
        Session session = sessionFactory.openSession();
        Transaction transaction = session.beginTransaction();
        Classes classes = (Classes) session.get(Classes.class, 2L);
        Set students = classes.getStudents();
        List sList = new ArrayList(students);
        for (int i = 0; i < sList.size(); i++) {
            if (sList.get(i).getSid().longValue() == 3
                    || sList.get(i).getSid().longValue() == 5) {
                sList.remove(sList.get(i));
                i--;
            }
        }
         students = new HashSet(sList);
         classes.setStudents(students);
         transaction.commit();
         session.close();
    }

但是只能查询到，无法加载更新，请教各位大神，如何处理，谢谢谢谢谢~~