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/*
 * Copyright (c) 2008, 2009, 2011 Oracle, Inc. 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.
 */
package javax.persistence;

/**
 * Interface used to interact with the second-level cache.
 * If a cache is not in use, the methods of this interface have
 * no effect, except for contains, which returns false.
 *
 * @since Java Persistence 2.0
 */
public interface Cache {

  /**
   * Whether the cache contains data for the given entity.
   *
   * @param cls        entity class
   * @param primaryKey primary key
   * @return boolean indicating whether the entity is in the cache
   */
  public boolean contains(Class cls, Object primaryKey);

  /**
   * Remove the data for the given entity from the cache.
   *
   * @param cls        entity class
   * @param primaryKey primary key
   */
  public void evict(Class cls, Object primaryKey);

  /**
   * Remove the data for entities of the specified class (and its
   * subclasses) from the cache.
   *
   * @param cls entity class
   */
  public void evict(Class cls);

  /**
   * Clear the cache.
   */
  public void evictAll();

  /**
   * Return an object of the specified type to allow access to the provider-specific API.
   * 
   * If the provider's Cache implementation does not support the specified class, the
   * PersistenceException is thrown.
   *
   * @param cls the class of the object to be returned. This is normally either the
   *            underlying Cache implementation class or an interface that it implements.
   * @return an instance of the specified class
   * @throws PersistenceException if the provider does not support the call
   */
  public  T unwrap(Class cls);

}