org.hibernate.loader.plan.spi.BidirectionalEntityReference Maven / Gradle / Ivy
/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2013, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
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*/
package org.hibernate.loader.plan.spi;
/**
* Represents the circular side of a bi-directional entity association. Wraps a reference to the associated
* (target) EntityReference.
*
* The {@link org.hibernate.loader.plan.exec.spi.EntityReferenceAliases} for this object is the same as
* for its target EntityReference, and can be looked up via
* {@link org.hibernate.loader.plan.exec.spi.AliasResolutionContext#resolveEntityReferenceAliases(String)}
* using the value returned by {@link #getQuerySpaceUid()}.
*
* This relies on reference lookups against the EntityReference instances, therefore this allows representation of the
* circularity but with a little protection against potential stack overflows. This is unfortunately still a cyclic
* graph. An alternative approach is to make the graph acyclic (DAG) would be to follow the process I adopted in the
* original HQL Antlr v3 work with regard to always applying an alias to the "persister reference", even where that
* meant creating a generated, unique identifier as the alias. That allows other parts of the tree to refer to the
* "persister reference" by that alias without the need for potentially cyclic graphs (think ALIAS_REF in the current
* ORM parser). Those aliases can then be mapped/catalogued against the "persister reference" for retrieval as needed.
*
* @author Steve Ebersole
*/
public interface BidirectionalEntityReference extends EntityReference {
/**
* Get the targeted EntityReference
*
* @return The targeted EntityReference
*/
public EntityReference getTargetEntityReference();
/**
* The query space UID returned using {@link #getQuerySpaceUid()} must
* be the same as returned by {@link #getTargetEntityReference()#getQuerySpaceUid()}
*
* @return The query space UID.
*/
public String getQuerySpaceUid();
}