openjpa-lib/src/main/java/org/apache/openjpa/lib/rop/ResultList.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
 *
 * http://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.
 */
package org.apache.openjpa.lib.rop;

import java.io.Serializable;
import java.util.List;

import org.apache.openjpa.lib.util.Closeable;

/**
 * List interface that represents a potentially lazy ResultList instantiation.
 * A ResultList will typically be instantiated from a factory, and
 * will use a ResultObjectProvider for obtaining individual object
 * data representations. Depending on the support for scrolling inputs,
 * the list that is returned may use lazy instantiation of the
 * objects, and thus allow very large result sets to be obtained and
 * manipulated. Note that wrapping a ResultList in another Collection will
 * always instantiate the entire set of elements contained in the
 * ResultList. This may not always be desirable, since the list may
 * be very large.
 *
 * @author Marc Prud'hommeaux
 */
public interface ResultList<E> extends List<E>, Serializable, Closeable {

    /**
     * Returns true if the provider backing this list is open.
     */
    boolean isProviderOpen();

    /**
     * Get the opaque user object attached to this receiver.
     */
    Object getUserObject();

    /**
     * Set the opaque user object to this receiver.
     */
    void   setUserObject(Object opaque);

    /**
     * Close the list.
     */
    @Override void close();

    /**
     * Returns true if the list has been closed.
     */
    boolean isClosed();
}