001/*
002 * The contents of this file are subject to the terms of the Common Development and
003 * Distribution License (the License). You may not use this file except in compliance with the
004 * License.
005 *
006 * You can obtain a copy of the License at legal/CDDLv1.0.txt. See the License for the
007 * specific language governing permission and limitations under the License.
008 *
009 * When distributing Covered Software, include this CDDL Header Notice in each file and include
010 * the License file at legal/CDDLv1.0.txt. If applicable, add the following below the CDDL
011 * Header, with the fields enclosed by brackets [] replaced by your own identifying
012 * information: "Portions Copyright [year] [name of copyright owner]".
013 *
014 * Copyright 2008 Sun Microsystems, Inc.
015 */
016package org.forgerock.opendj.config;
017
018import java.util.Collection;
019import java.util.Collections;
020
021import org.forgerock.opendj.config.client.ClientConstraintHandler;
022import org.forgerock.opendj.config.server.ServerConstraintHandler;
023
024/**
025 * An interface for enforcing constraints and dependencies between managed
026 * objects and their properties. Constraints express relationships between
027 * managed objects and their properties, for example:
028 * <ul>
029 * <li>referential integrity: where one managed object references another a
030 * constraint can enforce referential integrity. The constraint can prevent
031 * creation of references to non-existent managed objects, and also prevent
032 * deletion of referenced managed objects
033 * <li>property dependencies: for example, when a boolean property is
034 * <code>true</code>, one or more additional properties must be specified. This
035 * is useful for features like SSL, which when enabled, requires that various
036 * SSL related configuration options are specified
037 * <li>property constraints: for example, when an upper limit property must not
038 * have a value which is less than the lower limit property.
039 * </ul>
040 * On the client-side constraints are enforced immediately before a write
041 * operation is performed. That is to say, immediately before a new managed
042 * object is created, changes to a managed object are applied, or an existing
043 * managed object is deleted.
044 */
045public abstract class Constraint {
046
047    /**
048     * Creates a new constraint.
049     */
050    protected Constraint() {
051        // No implementation required.
052    }
053
054    /**
055     * Gets the client-side constraint handlers which will be used to enforce
056     * this constraint in client applications. The default implementation is to
057     * return an empty set of client constraint handlers.
058     *
059     * @return Returns the client-side constraint handlers which will be used to
060     *         enforce this constraint in client applications. The returned
061     *         collection must not be <code>null</code> but maybe empty
062     *         (indicating that the constraint can only be enforced on the
063     *         server-side).
064     */
065    public Collection<ClientConstraintHandler> getClientConstraintHandlers() {
066        return Collections.emptySet();
067    }
068
069    /**
070     * Gets the server-side constraint handlers which will be used to enforce
071     * this constraint within the server. The default implementation is to
072     * return an empty set of server constraint handlers.
073     *
074     * @return Returns the server-side constraint handlers which will be used to
075     *         enforce this constraint within the server. The returned
076     *         collection must not be <code>null</code> and must not be empty,
077     *         since constraints must always be enforced on the server.
078     */
079    public Collection<ServerConstraintHandler> getServerConstraintHandlers() {
080        return Collections.emptySet();
081    }
082
083    /**
084     * Initializes this constraint. The default implementation is to do nothing.
085     *
086     * @throws Exception
087     *             If this constraint could not be initialized.
088     */
089    protected void initialize() throws Exception {
090        // Default implementation is to do nothing.
091    }
092
093}