foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/indirection/IndirectContainer.java

/*
 * Copyright (c) 1998, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation from Oracle TopLink
package org.eclipse.persistence.indirection;


/**
 * <b>Purpose</b>:
 * <p>
 * Define an interface for a Container that can also act as an EclipseLink
 * "indirection" object; i.e. the Container will only read its contents from
 * the database when necessary (typically, on receipt of the first
 * Container-related message).
 * </p>
 *
 * @see org.eclipse.persistence.internal.indirection.TransparentIndirectionPolicy
 * @author Big Country
 *    @since TOPLink/Java 2.5
 */
public interface IndirectContainer<C> {

    /**
     * PUBLIC:
     * This is used by the indirection policy to build the
     * UOW clone of the container.
     * @return org.eclipse.persistence.indirection.ValueHolderInterface A representation of the valueholder  * which this container uses
     */
    ValueHolderInterface<C> getValueHolder();

    /**
     * PUBLIC:
     * Return whether the contents have been read from the database.
     * This is used periodically by the indirection policy to determine whether
     * to trigger the database read.
     */
    boolean isInstantiated();

    /**
     * PUBLIC:
     * Set the valueHolder.
     * This is used by the indirection policy to build the
     * UOW clone of the container.
     */
    void setValueHolder(ValueHolderInterface<C> valueHolder);
}