net.java.dev.webdav.jaxrs.xml.conditions.NoExternalEntities Maven / Gradle / Ivy

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/*
 * #%L
 * WebDAV Support for JAX-RS
 * %%
 * Copyright (C) 2008 - 2014 The java.net WebDAV Project
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as
 * published by the Free Software Foundation, either version 3 of the 
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public 
 * License along with this program.  If not, see
 * .
 * #L%
 */

package net.java.dev.webdav.jaxrs.xml.conditions;

import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlType;

import net.java.dev.webdav.util.Utilities;

/**
 * WebDAV no-external-entities Precondition XML Element.
 * 
 * 
 * This is a singleton. All instances are absolutely identical, hence can be compared using {@code ==} and share one unique hash code. Use
 * {@link #NO_EXTERNAL_ENTITIES} always.
 * 
 * 
 * @author Markus KARG ([email protected])
 * 
 * @see Chapter 16 "Precondition/Postcondition XML Elements" of RFC
 *      4918 "HTTP Extensions for Web Distributed Authoring and Versioning (WebDAV)"
 */
@XmlRootElement(name = "no-external-entities")
@XmlType(factoryMethod = "createSingleton")
public final class NoExternalEntities {
	/**
	 * Singleton instance, providing improved performance and the ability to compare by same instance.
	 * 
	 * @since 1.2
	 */
	public static final NoExternalEntities NO_EXTERNAL_ENTITIES = new NoExternalEntities();

	/**
	 * Singleton factory to be used solely by JAXB.
	 */
	@SuppressWarnings("unused")
	private static final NoExternalEntities createSingleton() {
		return NO_EXTERNAL_ENTITIES;
	}

	/**
	 * @deprecated Since 1.2. Use {@link #NO_EXTERNAL_ENTITIES} instead to obtain a singleton. In future releases this will have {@code private} visibility.
	 */
	@Deprecated
	public NoExternalEntities() {
		// For unmarshalling only.
	}

	@Override
	public final boolean equals(final Object object) {
		return object instanceof NoExternalEntities;
	}

	@Override
	public final int hashCode() {
		return 1;
	}

	@Override
	public final String toString() {
		return Utilities.toString(this);
	}
}