java - Hibernate @ManyToOne @JoinColumn is always null -

i'm trying implement one-to-many relation between 2 tables using hibernate. here code:

@entity public class board { @id @column(name = "board_id") @generatedvalue private long id;  @column private string owner;  @column private string title;  @column private string refresh;  @column private timestamp  createdate;  @column private timestamp modifydate;  @onetomany(mappedby="board", cascade=cascadetype.all) private list<item> items;  public long getid() {     return id; } public void setid(long id) {     this.id = id; }  public string getowner() {     return owner; } public void setowner(string owner) {     this.owner = owner; }  public string gettitle() {     return title; } public void settitle(string title) {     this.title = title; }  public string getrefresh() {     return refresh; } public void setrefresh(string refresh) {     this.refresh = refresh; }  public timestamp getcreatedate() {     return createdate; } public void setcreatedate(timestamp createdate) {     this.createdate = createdate; }  public timestamp getmodifydate() {     return modifydate; } public void setmodifydate(timestamp modifydate) {     this.modifydate = modifydate; }  public list<item> getitems() {     return items; } public void setitems(list<item> items) {     this.items = items; } } 

and second table:

@entity public class item { public enum type {        link,      image,       presentation;   }  public enum javascript {        enable,      disable;   }    @id @column @generatedvalue private long id;  @manytoone(fetch = fetchtype.eager)   @joincolumn(name = "board_id")   private board board;   @column private type type;  @column(length = 10000) private string link;  @column private string image;  @column private string presentation;  @column private string time;  @column private javascript javascript;  @column private string first;  @column private string last;  @transient private multipartfile imagefile;  @transient private multipartfile presentationfile;  public long getid() {     return id; } public void setid(long id) {     this.id = id; }  public board getboard() {     return board; } public void setboard(board board) {     this.board = board; }  public type gettype() {     return type; } public void settype(type type) {     this.type = type; }  public string getlink() {     return link; } public void setlink(string link) {     this.link = link; }  public string getimage() {     return image; } public void setimage(string image) {     this.image = image; } public string getpresentation() {     return presentation; } public void setpresentation(string presentation)  {     this.presentation = presentation; }  public string gettime() {     return time; } public void settime(string time) {     this.time = time; }  public javascript getjavascript() {     return javascript; } public void setjavascript(javascript javascript) {     this.javascript = javascript; }  public string getfirst() {     return first; } public void setfirst(string first) {     this.first = first; }  public string getlast()  {     return last; } public void setlast(string last) {     this.last = last; }  public multipartfile getimagefile() {     return imagefile; } public void setimagefile(multipartfile imagefile) {     this.imagefile = imagefile; }  public multipartfile getpresentationfile() {     return presentationfile; } public void setpresentationfile(multipartfile presentationfile)  {     this.presentationfile = presentationfile; } } 

but can't working. board_id null in item table. hibernate output looks strange:

hibernate: insert board (board_id, createdate, modifydate, owner, refresh, title) values (null, ?, ?, ?, ?, ?) hibernate: insert item (id, board_id, first, image, javascript, last, link, presentation, time, type) values (null, ?, ?, ?, ?, ?, ?, ?, ?, ?) 

any ideas?

to expand on comment @antoniossss, need set relation on both sides before persisting.

// create owning entity first board board = new board(); // create child entities item item1 = new item(); item1.setboard(board); // set relation on item side board.getitems().add(item1); // set relation on board side 

also note considered practice initialize collection fields immediately, board#getitems() never returns null.