| /* |
| * 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; |
| |
| |
| /** |
| * <b>Purpose</b>:Indicates an object that should not be returned from |
| * query execution. |
| * <p> |
| * 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. |
| * <p> |
| * 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. |
| * <p> |
| * Can be used in other instances where returning null is ambiguous. |
| * <p> |
| * 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; |
| } |
| } |
