org.eclipse.persistence.internal.helper.InvalidObject Maven / Gradle / Ivy

Go to download

Show more of this group Show more artifacts with this name
Show all versions of eclipselink Show documentation

EclipseLink build based upon Git transaction f2b9fc5

The newest version!

/*
 * Copyright (c) 1998, 2020 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.helper;


/**
 * Purpose:Indicates an object that should not be returned from
 * query execution.
 * 
 * When conforming if checkEarly return finds a matching object by exact primary
 * key, but that object is deleted, want to return null from query execution.
 * 

 * However if null is returned from checkEarly return that will indicate that
 * no object was found and to go to the database.  Hence returning null is not
 * enough, something else needed to be returned, indicating not only that
 * checkEarlyReturn had failed but query execution should not proceed.
 * 

 * Can be used in other instances where returning null is ambiguous.
 * 
 * Implements singleton pattern
 * @author  Stephen McRitchie
 */
public class InvalidObject {
    public static final InvalidObject instance = new InvalidObject();

    private InvalidObject() {
    }

    /**
     * @return singleton invalid object.
     */
    public static InvalidObject instance() {
        return instance;
    }
}