/* * $Id: UserDatabase.java 54929 2004-10-16 16:38:42Z germuska $  * * Copyright 2000-2004 Apache Software Foundation * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *     http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */package org.apache.struts.examples.mailreader;/** * <p>A <strong>Data Access Object</strong> (DAO) interface describing * the available operations for retrieving and storing {@link User}s * (and their associated {@link Subscription}s) in some persistence layer * whose characteristics are not specified here.  One or more implementations * will be created to perform the actual I/O that is required.</p> * * @version $Rev: 54929 $ $Date: 2004-10-16 09:38:42 -0700 (Sat, 16 Oct 2004) $ * @since Struts 1.1 */public interface UserDatabase {    // --------------------------------------------------------- Public Methods    /**     * <p>Create and return a new {@link User} defined in this user database.     * </p>     *     * @param username Username of the new user     *     * @exception IllegalArgumentException if the specified username     *  is not unique     */    public User createUser(String username);    /**     * <p>Finalize access to the underlying persistence layer.</p>     *     * @exception Exception if a database access error occurs     */    public void close() throws Exception;    /**     * <p>Return the existing {@link User} with the specified username,     * if any; otherwise return <code>null</code>.</p>     *     * @param username Username of the user to retrieve     * @throws ExpiredPasswordException if user password has expired     * and must be changed     */    public User findUser(String username) throws ExpiredPasswordException;    /**     * <p>Return the set of {@link User}s defined in this user database.</p>     */    public User[] findUsers();    /**     * <p>Initiate access to the underlying persistence layer.</p>     *     * @exception Exception if a database access error occurs     */    public void open() throws Exception;    /**     * Remove the specified {@link User} from this database.     *     * @param user User to be removed     *     * @exception IllegalArgumentException if the specified user is not     *  associated with this database     */    public void removeUser(User user);    /**     * <p>Save any pending changes to the underlying persistence layer.</p>     *     * @exception Exception if a database access error occurs     */    public void save() throws Exception;}