api/src/main/java/javax/jdo/Extent.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * Extent.java
 *
 */

package javax.jdo;

import java.util.Iterator;

/**
 * Instances of the <code>Extent</code> class represent the entire collection of instances in the
 * data store of the candidate class or interface possibly including its subclasses or
 * subinterfaces.
 *
 * <p>The <code>Extent</code> instance has two possible uses:
 *
 * <ol>
 *   <li>to iterate all instances of a particular class or interface
 *   <li>to execute a <code>Query</code> in the data store over all instances of a particular class
 *       or interface
 * </ol>
 *
 * @version 2.1
 */
public interface Extent<E> extends Iterable<E>, AutoCloseable {

  /**
   * Returns an iterator over all the instances in the <code>Extent</code>. The behavior of the
   * returned iterator might depend on the setting of the <code>ignoreCache</code> flag in the
   * owning <code>PersistenceManager</code>.
   *
   * @return an iterator over all instances in the <code>Extent</code>
   */
  Iterator<E> iterator();

  /**
   * Returns whether this <code>Extent</code> was defined to contain subclasses.
   *
   * @return true if this <code>Extent</code> was defined to contain instances that are of a
   *     subclass type.
   */
  boolean hasSubclasses();

  /**
   * An <code>Extent</code> contains all instances of a particular class or interface in the data
   * store; this method returns the <code>Class</code> of the instances represented by this Extent.
   *
   * @return the <code>Class</code> of instances of this <code>Extent</code>.
   */
  Class<E> getCandidateClass();

  /**
   * An <code>Extent</code> is managed by a <code>PersistenceManager</code>; this method gives
   * access to the owning <code>PersistenceManager</code>.
   *
   * @return the owning <code>PersistenceManager</code>
   */
  PersistenceManager getPersistenceManager();

  /**
   * Close all <code>Iterator</code>s associated with this <code>Extent</code> instance. <code>
   * Iterator</code>s closed by this method will return <code>false</code> to <code>hasNext()</code>
   * and will throw <code>NoSuchElementException</code> on <code>next()</code>. The <code>Extent
   * </code> instance can still be used as a parameter of <code>Query.setExtent</code>, and to get
   * an <code>Iterator</code>.
   */
  void closeAll();

  /**
   * Close an <code>Iterator</code> associated with this <code>Extent</code> instance. <code>
   * Iterator</code>s closed by this method will return <code>false</code> to <code>hasNext()</code>
   * and will throw <code>NoSuchElementException</code> on <code>next()</code>. The <code>Extent
   * </code> instance can still be used as a parameter of <code>Query.setExtent</code>, and to get
   * an <code>Iterator</code>.
   *
   * @param it an <code>Iterator</code> obtained by the method <code>iterator()</code> on this
   *     <code>Extent</code> instance.
   */
  void close(Iterator<E> it);

  /**
   * Don't use this method directly; use <code>closeAll()</code> instead. It is intended for use
   * with try-with-resources.
   */
  void close();

  /**
   * Get the fetch plan associated with this Extent.
   *
   * @return the fetch plan
   * @since 2.0
   */
  FetchPlan getFetchPlan();
}