java - Hibernate only saving 2 of 3 values in database -

i trying create entity called muziekstuk entitys called instrument , componist created join-table 3 foreign keys id's of muziekstuk instrument , componist.

muziekstuk , instrument created , componist select dropdown

this action code:

    muziekstukdaoimpl reg = new muziekstukdaoimpl();     componistdaoimpl com = new componistdaoimpl();      int componistid = integer.parseint(mcomponist);     componist componist = (componist) com.getbyid(componistid);      instrument i1 = new instrument(minstrument1, integer.parseint(maantal1));      muziekstuk muziekstuk = new muziekstuk(mtitel,mgenre,componist,i1);     reg.save(muziekstuk); 

it make new instrument , muziekstuk in join table id of componist null :s know why?

here rest of code: muziekstuk:

@entity @table(name = "stud1630651.mfmuziekstuk") public class muziekstuk {   @id @generatedvalue(strategy=generationtype.auto, generator="my_entity_seq_gen") @sequencegenerator(name="my_entity_seq_gen", sequencename="hibernate_sequence_muziekstuk") @column(name = "id") private int id;  @column(name = "titel") private string titel;  @column(name = "genre") private string genre;  @onetoone(cascade=cascadetype.all)   @jointable(name="mfmuziekstukjoin",joincolumns= {@joincolumn(name="muziekstukid")},inversejoincolumns= {@joincolumn(name="componistid")}) private componist componist;  @onetoone(cascade=cascadetype.all)   @jointable(name="mfmuziekstukjoin",joincolumns= {@joincolumn(name="muziekstukid")},inversejoincolumns= {@joincolumn(name="instrumentid")}) private instrument instrument;   public muziekstuk(string titel, string genre, componist componist, instrument instrument){     this.titel = titel;     this.genre = genre;     this.componist = componist;     this.instrument = instrument; }  public muziekstuk(int id, string titel, string genre, componist componist, instrument instrument){     this.id = id;     this.titel = titel;     this.genre = genre;     this.componist = componist;     this.instrument = instrument; }   //getters , setters 

componist:

@entity @table(name = "stud1630651.mfcomponist")   public class componist {  @id @generatedvalue(strategy=generationtype.auto, generator="my_entity_seq_gen") @sequencegenerator(name="my_entity_seq_gen", sequencename="hibernate_sequence_componist") @column(name = "id") private int id;  @column(name = "naam")   private string naam;  @column(name = "land")   private string land;  @column(name = "tijdvlak") private string tijdvlak;  @column(name = "composities") private string composities;   public componist(int id, string naam, string land, string tijdvlak, string composities){     this.id = id;     this.naam = naam;     this.land = land;     this.tijdvlak = tijdvlak;     this.composities = composities; }  public componist(string naam, string land, string tijdvlak, string composities){     this.naam = naam;     this.land = land;     this.tijdvlak = tijdvlak;     this.composities = composities; }  public componist(){ }  //getters , setters 

instrument:

@entity @table(name = "stud1630651.mfcomponist")   public class componist {  @id @generatedvalue(strategy=generationtype.auto, generator="my_entity_seq_gen") @sequencegenerator(name="my_entity_seq_gen", sequencename="hibernate_sequence_componist") @column(name = "id") private int id;  @column(name = "naam")   private string naam;  @column(name = "land")   private string land;  @column(name = "tijdvlak") private string tijdvlak;  @column(name = "composities") private string composities;   public componist(int id, string naam, string land, string tijdvlak, string composities){     this.id = id;     this.naam = naam;     this.land = land;     this.tijdvlak = tijdvlak;     this.composities = composities; }  public componist(string naam, string land, string tijdvlak, string composities){     this.naam = naam;     this.land = land;     this.tijdvlak = tijdvlak;     this.composities = composities; }  public componist(){ }  //getters , setters 

save function in dao:

@override public void save(object t) {   muziekstuk muziekstuk = (muziekstuk) t;   system.out.println(muziekstuk.getcomponist().getid());   session session = null;     transaction transaction = null;     try {         session = hibernateutil.getsessionfactory().opensession();         transaction = session.begintransaction();        session.saveorupdate(muziekstuk);       transaction.commit();      } catch (exception e) {         if (transaction != null) {             transaction.rollback();           system.out.println("exception");           e.printstacktrace();       }     } {         if (session != null) {             session.close();         }     }    } 

this sql trace:

hibernate: select componist0_.id id1_2_0_, componist0_.composities composit2_2_0_, componist0_.land       land3_2_0_, componist0_.naam naam4_2_0_, componist0_.tijdvlak tijdvlak5_2_0_ stud1630651.mfcomponist componist0_ componist0_.id=? hibernate: select hibernate_sequence_muziekstuk.nextval dual hibernate: select hibernate_sequence_instrument.nextval dual hibernate: insert stud1630651.mfinstrument (hoeveelheid, naam, id) values (?, ?, ?) hibernate: insert stud1630651.mfmuziekstuk (genre, titel, id) values (?, ?, ?) hibernate: insert mfmuziekstukjoin (instrumentid, muziekstukid) values (?, ?) 

ther should 3 ? in muziekstukjoin

it turns out join table can refer 1 table not 2 should make 2 join tables if wondering.