java - Persist 1-m entities with composite primary key in hibernate -

i have below 1-m relationship on entities mentor students. mentor has composite primary key use foreign key in student

@entity public class mentor implements serializable {     private static final long serialversionuid = 1l;     @id     private mentorpk id;     private string email;     @onetomany(mappedby="mentor")     private set<student> students;      public mentorpk getid() {         return id;     }                 //getters , setters }  @embeddable public class mentorpk implements serializable {      private static final long serialversionuid = 1l;     private string name;     private string add;     //getters , setters     //override equals , hashcode }   @entity public class student implements serializable{     private static final long serialversionuid = 1l;     @id     @generatedvalue(strategy=generationtype.auto)     private int id;     private string name;          @manytoone     @mapsid("id")     @joincolumns({         @joincolumn(name="name_fk", referencedcolumnname="name"),         @joincolumn(name="address_fk", referencedcolumnname="address")     })     private mentor mentor;      //getters , setters } 

i persist above below mentor persisted student table empty.

how can persist mentor students?

set<student> students = new hashset<student>();  student s1 = new student(); s1.setname("student 1");  student s2 = new student(); s2.setname("student 2");  students.add(s1); students.add(s2);  mentorpk mpk = new mentorpk(); mpk.setaddress("c"); mpk.setname("d");  mentor m = new mentor(); m.setid(mpk); m.setemail("emaill"); m.setstudents(students);  studentmanager.savementor(m); 

try changing annotation of students field

@onetomany(mappedby="mentor", cascade = cascadetype.persist)