base/src/main/java/org/apache/commons/chain2/impl/CatalogFactoryBase.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.commons.chain2.impl;

import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.commons.chain2.Catalog;
import org.apache.commons.chain2.CatalogFactory;

/**
 * <p>A simple implementation of {@link CatalogFactory}.</p>
 *
 * @param <K> Context key type
 * @param <V> Context value type
 * @param <C> Type of the context associated with this command
 * @version $Id$
 */
public class CatalogFactoryBase<K, V, C extends Map<K, V>> extends CatalogFactory<K, V, C> {

    // ----------------------------------------------------------- Constructors

    /**
     * <p>Construct an empty instance of {@link CatalogFactoryBase}.  This
     * constructor is intended solely for use by {@link CatalogFactory}.</p>
     */
    public CatalogFactoryBase() {
    }

    // ----------------------------------------------------- Instance Variables

    /**
     * <p>The default {@link Catalog} for this {@link CatalogFactory}.</p>
     */
    private Catalog<K, V, C> catalog = null;

    /**
     * <p>Map of named {@link Catalog}s, keyed by catalog name.</p>
     */
    private final Map<String, Catalog<K, V, C>> catalogs = new ConcurrentHashMap<String, Catalog<K, V, C>>();

    // --------------------------------------------------------- Public Methods

    /**
     * <p>Gets the default instance of Catalog associated with the factory
     * (if any); otherwise, return <code>null</code>.</p>
     *
     * @return the default Catalog instance
     */
    @Override
    public Catalog<K, V, C> getCatalog() {
        return catalog;
    }

    /**
     * <p>Sets the default instance of Catalog associated with the factory.</p>
     *
     * @param catalog the default Catalog instance
     */
    @Override
    public void setCatalog(Catalog<K, V, C> catalog) {
        this.catalog = catalog;
    }

    /**
     * <p>Retrieves a Catalog instance by name (if any); otherwise
     * return <code>null</code>.</p>
     *
     * @param name the name of the Catalog to retrieve
     * @return the specified Catalog
     */
    @Override
    public Catalog<K, V, C> getCatalog(String name) {
        return catalogs.get(name);
    }

    /**
     * <p>Adds a named instance of Catalog to the factory (for subsequent
     * retrieval later).</p>
     *
     * @param name    the name of the Catalog to add
     * @param catalog the Catalog to add
     */
    @Override
    public void addCatalog(String name, Catalog<K, V, C> catalog) {
        catalogs.put(name, catalog);
    }

    /**
     * <p>Return an <code>Iterator</code> over the set of named
     * {@link Catalog}s known to this {@link CatalogFactory}.
     * If there are no known catalogs, an empty Iterator is returned.</p>
     *
     * @return An Iterator of the names of the Catalogs known by this factory.
     */
    @Override
    public Iterator<String> getNames() {
        return catalogs.keySet().iterator();
    }

}