oracle.toplink.essentials.internal.helper.InvalidObject Maven / Gradle / Ivy
/*
* The contents of this file are subject to the terms
* of the Common Development and Distribution License
* (the "License"). You may not use this file except
* in compliance with the License.
*
* You can obtain a copy of the license at
* glassfish/bootstrap/legal/CDDLv1.0.txt or
* https://glassfish.dev.java.net/public/CDDLv1.0.html.
* See the License for the specific language governing
* permissions and limitations under the License.
*
* When distributing Covered Code, include this CDDL
* HEADER in each file and include the License file at
* glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable,
* add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your
* own identifying information: Portions Copyright [yyyy]
* [name of copyright owner]
*/
// Copyright (c) 1998, 2007, Oracle. All rights reserved.
/* Copyright (c) 2004, 2006, Oracle. All rights reserved. */
/*
DESCRIPTION
PRIVATE CLASSES
NOTES
MODIFIED (MM/DD/YY)
pkrogh 10/07/05 -
pkrogh 09/29/05 -
gyorke 08/09/05 - gyorke_10-essentials-directory-creation_050808
dmahar 08/04/05 -
pkrogh 08/28/04 - codeformat
smcritch 05/14/04 - smcritch_refactor_session_read031604
smcritch 04/26/04 - Creation
*/
package oracle.toplink.essentials.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
* @since release specific (what release of product did this appear in)
*/
public class InvalidObject {
public static final InvalidObject instance = new InvalidObject();
private InvalidObject() {
}
/**
* @return singleton invalid object.
*/
public static InvalidObject instance() {
return instance;
}
}