Path.java

/*
 * Copyright (c) 2008, 2009 Sun Microsystems. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
 * which accompanies this distribution.
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *     Linda DeMichiel - Java Persistence 2.0 - Version 2.0 (October 1, 2009)
 *     Specification available from http://jcp.org/en/jsr/detail?id=317
 */

// $Id: Path.java 20957 2011-06-13 09:58:51Z stliu $

package javax.persistence.criteria;

import javax.persistence.metamodel.PluralAttribute;
import javax.persistence.metamodel.SingularAttribute;
import javax.persistence.metamodel.Bindable;
import javax.persistence.metamodel.MapAttribute;

/**
 * Represents a simple or compound attribute path from a
 * bound type or collection, and is a "primitive" expression.
 *
 * @param <X>  the type referenced by the path
 * @since Java Persistence 2.0
 */
public interface Path<X> extends Expression<X> {
	/**
	 * Return the bindable object that corresponds to the
	 * path expression.
	 *
	 * @return bindable object corresponding to the path
	 */
	Bindable<X> getModel();

	/**
	 * Return the parent "node" in the path or null if no parent.
	 *
	 * @return parent
	 */
	Path<?> getParentPath();

	/**
	 * Create a path corresponding to the referenced
	 * single-valued attribute.
	 *
	 * @param attribute single-valued attribute
	 *
	 * @return path corresponding to the referenced attribute
	 */
	<Y> Path<Y> get(SingularAttribute<? super X, Y> attribute);

	/**
	 * Create a path corresponding to the referenced
	 * collection-valued attribute.
	 *
	 * @param collection collection-valued attribute
	 *
	 * @return expression corresponding to the referenced attribute
	 */
	<E, C extends java.util.Collection<E>> Expression<C> get(PluralAttribute<X, C, E> collection);

	/**
	 * Create a path corresponding to the referenced
	 * map-valued attribute.
	 *
	 * @param map map-valued attribute
	 *
	 * @return expression corresponding to the referenced attribute
	 */
	<K, V, M extends java.util.Map<K, V>> Expression<M> get(MapAttribute<X, K, V> map);

	/**
	 * Create an expression corresponding to the type of the path.
	 *
	 * @return expression corresponding to the type of the path
	 */
	Expression<Class<? extends X>> type();


	//String-based:

	/**
	 * Create a path corresponding to the referenced attribute.
	 *
	 * <p> Note: Applications using the string-based API may need to
	 * specify the type resulting from the <code>get</code> operation in order
	 * to avoid the use of <code>Path</code> variables.
	 *
	 * <pre>
	 *     For example:
	 *
	 *     CriteriaQuery<Person> q = cb.createQuery(Person.class);
	 *     Root<Person> p = q.from(Person.class);
	 *     q.select(p)
	 *      .where(cb.isMember("joe",
	 *                         p.<Set<String>>get("nicknames")));
	 *
	 *     rather than:
	 *
	 *     CriteriaQuery<Person> q = cb.createQuery(Person.class);
	 *     Root<Person> p = q.from(Person.class);
	 *     Path<Set<String>> nicknames = p.get("nicknames");
	 *     q.select(p)
	 *      .where(cb.isMember("joe", nicknames));
	 *  </pre>
	 *
	 * @param attributeName name of the attribute
	 *
	 * @return path corresponding to the referenced attribute
	 *
	 * @throws IllegalStateException if invoked on a path that
	 * corresponds to a basic type
	 * @throws IllegalArgumentException if attribute of the given
	 * name does not otherwise exist
	 */
	<Y> Path<Y> get(String attributeName);
}