[hibernate-issues] [Hibernate-JIRA] Created: (ANN-494) Determine Referenced Entity For Embeddable types from the parameterised type

[Edward Costello (JIRA)]

Determine Referenced Entity For Embeddable types from the parameterised type
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         Key: ANN-494
         URL: http://opensource.atlassian.com/projects/hibernate/browse/ANN-494
     Project: Hibernate Annotations
        Type: Improvement

  Components: binder  
    Versions: 3.2.0.cr1    
    Reporter: Edward Costello


When a collection is mapped using @ManyToOne or @CollectionOfElements, the entity in the collection is derived from the parametrised type of the collection. e.g. there is no need to explicitly indicate the elements of the following collection are books.

@ManyToOne
Set<Book> books;

It would be nice if the same kind of discovery could be applied to Embeddable types when contained in a CollectionOfElements. E.g. it would be nice if Hibernate could derive that the embedded Versioned references a Book in the example below

@CollectionOfElements
Set<Versioned<Book>>;

@Embeddable
class Versioned<T> {
    T rightSide;
    Date date;
}

Even if it wasn't derived, it would be good to be able to specify it. Currently the only way to make the above work is to create a subclass of Versioned that explicitly binds the type parameter to Book. Without this the below exception is thrown while building the session factory

Exception in thread "main" java.lang.IllegalStateException: Property rightSide has an unbound type and no explicit target entity.
   at org.hibernate.cfg.AnnotationBinder.addElementsOfAClass(AnnotationBinder.java:946)
   at org.hibernate.cfg.AnnotationBinder.fillComponent(AnnotationBinder.java:1655)
   at org.hibernate.cfg.annotations.CollectionBinder.bindManyToManySecondPass(CollectionBinder.java:1054)
    at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:543)
   at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:484)
   at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:43)
   at org.hibernate.cfg.annotations.CollectionBinder.bind(CollectionBinder.java:377)
   at org.hibernate.cfg.AnnotationBinder.processElementAnnotations(AnnotationBinder.java:1476)
   at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:706)
   at org.hibernate.cfg.AnnotationConfiguration.processArtifactsOfType(AnnotationConfiguration.java:452)
   at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:268)
   at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1210)


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