Hibernate @OneToOne self join with OR in join clause

Question

I have a @OneToOne annotation which I want to join on 2 possible columns. I know how to do it with a plain SQL query, but I have no idea how this could work with hibernate annotations.

Following entity:

@Entity
public class Foo {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @OneToOne
    @JoinColumn(name = "cancelRecord")
    private Foo cancelRecord;

    private String externalId;
    private String externalCancellationId;
}

and the corresponding database table:

create table Foo(
    id int identity(1,1) not null primary key, --primary key
    cancelRecord int,
    externalId varchar(100),
    externalCancellationId varchar(100)
)

So far cancelRecord is only joined on that column. Now I want it to join on either cancelRecord or externalCancellationId . A valid SQL query for that would be:

SELECT f.* 
FROM Foo f 
        INNER JOIN Foo fo 
        ON (f.cancelRecord = fo.id 
        OR f.externalCancellationId = fo.externalId)

The crucial part about this query is the OR in the join clause (f.cancelRecord = fo.id **OR** f.externalCancellationId = fo.externalId) .

I assume that this is not possible with @JoinColumn and I'd need to rely on @JoinFormula in some way.

Is that assumption right? If so, would I simply need to copy the above query as @JoinFormula ?

---

I tried to use this @JoinFoluma :

@OneToOne
@JoinFormula(value = "SELECT f.* 
        FROM Foo f 
        INNER JOIN Foo fo 
        ON (f.cancelRecord = fo.id 
        OR f.externalCancellationId = fo.externalId)")
private Foo cancelRecord;

This causes an NullPointerException when loading the spring context:

Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in class path resource [spring/test-database.xml]: Invocation of init method failed; nested exception is java.lang.NullPointerException
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1589)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:554)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:351)
    ... 43 common frames omitted
Caused by: java.lang.NullPointerException: null
    at org.hibernate.cfg.AnnotationBinder.bindOneToOne(AnnotationBinder.java:3185)
    at org.hibernate.cfg.AnnotationBinder.processElementAnnotations(AnnotationBinder.java:1798)
    at org.hibernate.cfg.AnnotationBinder.processIdPropertiesIfNotAlready(AnnotationBinder.java:961)
    at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:788)
    at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:250)
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:231)
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:274)
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.build(MetadataBuildingProcess.java:84)
    at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:474)
    at org.hibernate.boot.internal.MetadataBuilderImpl.build(MetadataBuilderImpl.java:85)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:689)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:724)
    at org.springframework.orm.hibernate5.LocalSessionFactoryBean.buildSessionFactory(LocalSessionFactoryBean.java:511)
    at org.springframework.orm.hibernate5.LocalSessionFactoryBean.afterPropertiesSet(LocalSessionFactoryBean.java:495)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1648)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1585)
    ... 50 common frames omitted

EDIT:

Exception resolved with this question , but sadly this again ends with an AND instead of an OR .

Answer 1

That will not work since the @JoinColumn or @JoinFormula are used to determine Foreign Key column value, so they don't work with multiple columns.

If you define multiple @JoinColumn or @JoinFormula , then the ON relationship will use an AND not an OR .

In your case, since you probably only want to read this association, as opposed to setting it using Hibernate, then you are better off using an SQL query instead.

Answer 2

You can use more than one @JoinColumn annotation. See an example below:

   @OneToOne
   @JoinColumns(
     {
       @JoinColumn(updatable=false,insertable=false, name="cancelRecord", referencedColumnName="cancelRecord"),
       @JoinColumn(updatable=false,insertable=false, name="other", referencedColumnName="other")
     }
   )
   private Foo cancelRecord;