JPA Hibernate One-to-One relationship

Question

I have a one-to-one relationship but hibernatetool complains when generating the schema  Here s an example that shows the problem    Entity public class Person        Id     public int id        OneToOne     public OtherInfo otherInfo       rest of attributes         Person has a one-to-one relationship with OtherInfo    Entity public class OtherInfo        Id      OneToOne mappedBy  otherInfo       public Person person       rest of attributes         Person is owning side of OtherInfo  OtherInfo is the owned side so person uses mappedBy to specify the attribute name  otherInfo  in Person   I get the following error when using hibernatetool to generate the database schema   org hibernate MappingException  Could not determine type for  Person  at table  OtherInfo  for columns   org hibernate mapping Column person           at org hibernate mapping SimpleValue getType SimpleValue java 292          at org hibernate mapping SimpleValue createIdentifierGenerator SimpleValue java 175          at org hibernate cfg Configuration iterateGenerators Configuration java 743          at org hibernate cfg Configuration generateDropSchemaScript Configuration java 854          at org hibernate tool hbm2ddl SchemaExport  lt init gt  SchemaExport java 128                Any idea why  Am I a doing something wrong or is this a Hibernate bug

User · Answer

I have a better way of doing this    Entity public class Person         OneToOne cascade  javax persistence CascadeType ALL        JoinColumn name     Id OtherInfo        public OtherInfo getOtherInfo           return otherInfo             That s all

User · Answer

JPA doesn t allow the  Id annotation on a OneToOne or ManyToOne mapping  What you are trying to do is one-to-one entity association with shared primary key  The simplest case is unidirectional one-to-one with shared key    Entity public class Person        Id     private int id        OneToOne      PrimaryKeyJoinColumn     private OtherInfo otherInfo       rest of attributes         The main problem with this is that JPA provides no support for shared primary key generation in OtherInfo entity  The classic book Java Persistence with Hibernate by Bauer and King gives the following solution to the problem using Hibernate extension    Entity public class OtherInfo        Id  GeneratedValue generator    customForeignGenerator        org hibernate annotations GenericGenerator          name    customForeignGenerator           strategy    foreign           parameters    Parameter name    property   value    person             private Long id        OneToOne mappedBy  otherInfo        PrimaryKeyJoinColumn     public Person person       rest of attributes         Also  see here

User · Answer

I think you still need the primary key property in the OtherInfo class    Entity public class OtherInfo        Id     public int id        OneToOne mappedBy  otherInfo       public Person person       rest of attributes         Also  you may need to add the  PrimaryKeyJoinColumn annotation to the other side of the mapping  I know that Hibernate uses this by default  But then I haven t used JPA annotations  which seem to require you to specify how the association wokrs

User · Answer

I m not sure you can use a relationship as an Id PrimaryKey in Hibernate

User · Answer

Try this   Entity   Table name  tblperson    public class Person    public int id   public OtherInfo otherInfo   Id   Here Id is autogenerated  Column name  id    GeneratedValue strategy GenerationType AUTO  public int getId         return id    public void setId int id        this id   id      OneToOne cascade   CascadeType ALL targetEntity OtherInfo class   JoinColumn name  otherInfo id     there should be a column otherInfo id in Person public OtherInfo getOtherInfo         return otherInfo    public void setOtherInfo OtherInfo otherInfo        this otherInfo  otherInfo    rest of attributes          Entity   Table name  tblotherInfo    public class OtherInfo    private int id   private Person person    Id   Column name  id    GeneratedValue strategy GenerationType AUTO  public Long getId         return id    public void setId Long id        this id   id        OneToOne mappedBy  OtherInfo  targetEntity Person class     public College getPerson         return person    public void setPerson Person person        this person   person         rest of attributes

User · Answer

This should be working too using JPA 2 0  MapsId annotation instead of Hibernate s GenericGenerator    Entity public class Person         Id      GeneratedValue     public int id        OneToOne      PrimaryKeyJoinColumn     public OtherInfo otherInfo       rest of attributes         Entity public class OtherInfo         Id     public int id        MapsId      OneToOne      JoinColumn name  id       public Person person       rest of attributes         More details on this in Hibernate 4 1 documentation under section 5 1 2 2 7

User · Answer

You just need to add  JoinColumn name  column name   to Host Entity relation   column name is the database column name in person table    Entity public class Person        Id     public int id        OneToOne      JoinColumn name  other info       public OtherInfo otherInfo       rest of attributes         Person has a one-to-one relationship with OtherInfo  mappedBy  var name  var name is variable name for otherInfo in Person class    Entity public class OtherInfo        Id      OneToOne mappedBy  otherInfo       public Person person       rest of attributes

[java] JPA Hibernate One-to-One relationship

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