001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.chain;
018    
019    
020    import java.util.Iterator;
021    
022    
023    /**
024     * <p>A {@link Catalog} is a collection of named {@link Command}s (or
025     * {@link Chain}s) that can be used to retrieve the set of commands that
026     * should be performed based on a symbolic identifier.  Use of catalogs
027     * is optional, but convenient when there are multiple possible chains
028     * that can be selected and executed based on environmental conditions.</p>
029     *
030     * @author Craig R. McClanahan
031     * @version $Revision: 480477 $ $Date: 2006-11-29 08:34:52 +0000 (Wed, 29 Nov 2006) $
032     */
033    
034    public interface Catalog {
035    
036    
037        /**
038         * <p>A default context attribute for storing a default {@link Catalog},
039         * provided as a convenience only.</p>
040         */
041        String CATALOG_KEY = "org.apache.commons.chain.CATALOG";
042    
043    
044        /**
045         * <p>Add a new name and associated {@link Command} or {@link Chain}
046         * to the set of named commands known to this {@link Catalog},
047         * replacing any previous command for that name.
048         *
049         * @param name Name of the new command
050         * @param command {@link Command} or {@link Chain} to be returned
051         *  for later lookups on this name
052         */
053        void addCommand(String name, Command command);
054    
055    
056        /**
057         * <p>Return the {@link Command} or {@link Chain} associated with the
058         * specified name, if any; otherwise, return <code>null</code>.</p>
059         *
060         * @param name Name for which a {@link Command} or {@link Chain}
061         *  should be retrieved
062         * @return The Command associated with the specified name.
063         */
064        Command getCommand(String name);
065    
066    
067    
068        /**
069         * <p>Return an <code>Iterator</code> over the set of named commands
070         * known to this {@link Catalog}.  If there are no known commands,
071         * an empty Iterator is returned.</p>
072         * @return An iterator of the names in this Catalog.
073         */
074        Iterator getNames();
075    
076    
077    }
078