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.<init>(SchemaExport.java:128)
        ...

Any idea why? Am I a doing something wrong or is this a Hibernate bug?

score 85 · Accepted Answer · edited Jun 07 '11 at 09:28

85

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.

edited Jun 07 '11 at 09:28

Will

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answered Apr 25 '09 at 13:45

topchef

19,091
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3

Great answer, just wanted to add that you may need to add the following annotation as well in your Person class (I had to to get things working correctly): `@Cascade({ CascadeType.ALL, CascadeType.DELETE_ORPHAN })` – Abdullah Jibaly Aug 25 '11 at 19:00
Thanks, it helped on my problem.. Do you know of anyway use only JPA annotations and avoid the hibernate one? – Elton Feb 06 '12 at 04:50
@Elton - if there is a way it must be in JPA 2.0 - I didn't look into this though. – topchef Feb 06 '12 at 23:01
1

It did work for me, but I had to add `optional=false` to the `@OneToOne` annotation. Otherwise I'd get an exception complaining that person was null. – Andre Aug 23 '13 at 16:03

score 23 · Answer 2 · answered Aug 27 '12 at 10:48

23

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.

answered Aug 27 '12 at 10:48

Mariusz

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[Link for the lazy](https://docs.jboss.org/hibernate/orm/4.1/manual/en-US/html_single/#d5e2666). I chose to use the Id annotation on the OneToOne class itself (OtherInfo in your example), but that only works in a child-parent scenario. Thanks for the answer! – Joe Jan 12 '13 at 14:25
2

Why did you specify `@JoinColumn` on `OtherInfo` rather than use `@PrimaryKeyJoinColumn`? – Idris Mokhtarzada Oct 23 '14 at 12:23

score 10 · Answer 3 · edited May 13 '14 at 14:38

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 ...
}

score 4 · Answer 4 · answered Apr 25 '09 at 06:12

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.

score 2 · Answer 5 · edited Dec 04 '12 at 18:43

2

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

edited Dec 04 '12 at 18:43

Community

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answered May 19 '11 at 16:24

Vodo-Siosk Baas

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Also the owned side, i.e. the side that has the foreign key must implement serialisable (with hiberate 4 /jpa 2) – dan carter Jul 23 '13 at 05:20

score 1 · Answer 6 · answered Apr 24 '09 at 21:55

1

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

answered Apr 24 '09 at 21:55

razenha

7,660
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score 1 · Answer 7 · edited Feb 16 '12 at 12:09

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 ...
}

JPA Hibernate One-to-One relationship

7 Answers7

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