java - Hibernate : @OneToOne gives null value -

i'm trying map onetoone relationship entity identifier : in schema person can have 0 or 1 user account, user_accounts table's id foreign key referencing person's id.

here's sample of class diagram :

i have used joined inheritance strategy.

schema :

• persons (id, ..., pk(id))
• customers (id, ..., pk(id), fk(id) rf persons(id))
• user_accounts(id, ..., pk(id), fk(id) rf persons(id))

here's sample of useraccount class :

    @entity     @table(name = "user_accounts")     public class useraccount extends core.business.model.mapping.entity implements serializable {          @id         @onetoone(targetentity = person.class, cascade = cascadetype.all)         @joincolumn(name = "id", referencedcolumnname = "id", nullable = false)         private registereduser user;          @column(name = "email_address")         private string emailaddress;          @column         private string hash;          @onetoone(mappedby = "useraccount",                   cascade  = cascadetype.all,                   fetch    = fetchtype.lazy)         private token token;           @override         public boolean equals(object o) {             if (this == o) return true;             if (o == null || getclass() != o.getclass()) return false;              useraccount = (useraccount) o;              return user.equals(that.user);         }          @override         public int hashcode() {             return user.hashcode();         }          useraccount() {         } } 

after useraccount returned dao, user null, cannot possible according model's constraints.

here's sql query generated hibernate :

select useraccoun0_.id id4_25_, useraccoun0_.updated_at updated_1_25_, useraccoun0_.email_address email_ad2_25_, useraccoun0_.hash hash3_25_, useraccoun0_1_.token_id token_id0_24_ user_accounts useraccoun0_ left outer join tokens__user_accounts useraccoun0_1_ on useraccoun0_.id=useraccoun0_1_.user_account_id useraccoun0_.email_address='xxx@xxx.com' , useraccoun0_.hash='e13d212084f7d594e4c540474c0981d99dfe581a'

there no join on persons table while expected fetch it.

if move registreduser @embeddable class , embed @embeddedid, relationship fetched, it's quite "ugly" proceed , hibernate specs @ the end of 2.2.3.1 section :

finally, can ask hibernate copy identifier associated entity. in hibernate jargon, known foreign generator jpa mapping reads better , encouraged