foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/internal/sequencing/Sequencing.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.internal.sequencing;

/**
 * <p>
 * <b>Purpose</b>: Define interface to use sequencing.
 * <p>
 * <b>Description</b>: This interface accessed through Session.getSequencing() method.
 * Used by EclipseLink internals to obtain sequencing values.
 * <p>
 * <b>Responsibilities</b>:
 * <ul>
 * <li> Provides sequencing objects and supporting APIs.
 * </ul>
 */
public interface Sequencing {
    // Possible return values for whenShouldAcquireValueForAll() method:
    // all classes should acquire sequencing value before insert;
    int BEFORE_INSERT = -1;

    // some classes should acquire sequencing value before insert, some after;
    int UNDEFINED = 0;

    // all classes should acquire sequencing value after insert;
    int AFTER_INSERT = 1;

    /**
     * INTERNAL:
     * Indicates when sequencing value should be acquired for all classes.
     * There are just three possible return values:
     * BEFORE_INSERT, UNDEFINED, AFTER_INSERT.
     * Used as a shortcut to avoid individual checks for each class:
     * shouldAcquireValueAfterInsert(Class cls).
     * Currently UNDEFINED only happens in a case of a SessionBroker:
     * session1 - BEFORE_INSERT, session2 - AFTER_INSERT
     */
    int whenShouldAcquireValueForAll();

    /**
     * INTERNAL:
     * Return the newly-generated sequencing value.
     * @param cls Class for which the sequencing value is generated.
     */
    Object getNextValue(Class<?> cls);

}