org.glassfish.config.support.Singleton Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of payara-embedded-all Show documentation
Payara-Embedded-All Distribution of the Payara Project
There is a newer version: 4.1.2.181
/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * Copyright (c) 2011-2012 Oracle and/or its affiliates. All rights reserved.
 *
 * The contents of this file are subject to the terms of either the GNU
 * General Public License Version 2 only ("GPL") or the Common Development
 * and Distribution License("CDDL") (collectively, the "License").  You
 * may not use this file except in compliance with the License.  You can
 * obtain a copy of the License at
 * https://glassfish.dev.java.net/public/CDDL+GPL_1_1.html
 * or packager/legal/LICENSE.txt.  See the License for the specific
 * language governing permissions and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file at packager/legal/LICENSE.txt.
 *
 * GPL Classpath Exception:
 * Oracle designates this particular file as subject to the "Classpath"
 * exception as provided by Oracle in the GPL Version 2 section of the License
 * file that accompanied this code.
 *
 * Modifications:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 *
 * Contributor(s):
 * If you wish your version of this file to be governed by only the CDDL or
 * only the GPL Version 2, indicate your decision by adding "[Contributor]
 * elects to include this software in this distribution under the [CDDL or GPL
 * Version 2] license."  If you don't indicate a single choice of license, a
 * recipient has the option to distribute your version of this file under
 * either the CDDL, the GPL Version 2 or to extend the choice of license to
 * its licensees as provided above.  However, if you add GPL Version 2 code
 * and therefore, elected the GPL Version 2 license, then the option applies
 * only if the new code is made subject to such option by the copyright
 * holder.
 */
package org.glassfish.config.support;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Annotation that qualifies a configuration element that can only exist
 * as a singleton in the configuration tree.
 *
 * When configuration elements are added to their parents through a
 * subclassing pattern, it can be difficult for the system to determine if this
 * element can exist as a singleton or a collection.
 *
 * For instance, when the parent contains :
 * 
 * @Element("*")
 * List getExtensions();
 * 
 *
 * A subclass of Extension can have a single or multiple instances stored
 * in the extensions list. Adding this annotation will qualify that only
 * one instance of the annotated configuration can be found in that
 * collection. Note that the collection can contain other instances of other
 * subclasses of Extension.
 *
 * @author Jerome Dochez
 */
@Retention(RUNTIME)
@Target(ElementType.TYPE)
public @interface Singleton {
}