OneToOne association cannot be fetched with a single query in Hibernate

Environment

• Red Hat JBoss Enterprise Application Platform (EAP) 7
• Hibernate 5

Issue

• A OneToOne association is defined between two entities (e.g. Customer and Address)
• An HQL/JPAQL query like select c from Customer c join fetch c.address results in two distinct SQL queries

Resolution

• This issue (dating back to Hibernate 3) has been Content from hibernate.atlassian.net is not included.addressed in the upstream Hibernate project and will be addressed in a future release¹ of JBoss EAP.
• It may be feasible to work around the issue using a declared ManyToOne association with code adapting the getter/setter to a OneToOne style interface (that can later be removed) for use by application code which references the entity.

Root Cause

This is a known defect (Content from hibernate.atlassian.net is not included.HHH-3930).

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