/*

  * Copyright 1999-2001,2004 The 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.commons.workflow.base;

 import java.util.HashMap;

 import org.apache.commons.workflow.Activity;

 import org.apache.commons.workflow.Registry;

 /**

  * <p><strong>BaseRegistry</strong> is a convenient base class for more

  * sophisticated <code>Registry</code> implementations.</p>

  *

  * @version $Revision: 155475 $ $Date: 2005-02-26 13:31:11 +0000 (Sat, 26 Feb 2005) $

  * @author Craig R. McClanahan

  */

 public class BaseRegistry implements Registry {

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

     /**

      * The set of Activity instances registered with this Registry, keyed

      * by identifier.

      */

     protected HashMap activities = new HashMap();

     // ------------------------------------------------------------- Properties

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

     /**

      * Add a new Activity to the set of Activity instances known to this

      * Registry.

      *

      * @param activity The new activity to be added

      */

     public void addActivity(Activity activity) {

         activities.put(activity.getId(), activity);

     }

     /**

      * Clear any existing Activity instances registered with this Registry.

      */

     public void clear() {

         activities.clear();

     }

     /**

      * Return the complete set of Activity instances associated with

      * this Activity.  If there are no such registered Activity instances,

      * a zero-length array is returned.

      */

     public Activity[] findActivities() {

         Activity results[] = new Activity[activities.size()];

         return ((Activity[]) activities.values().toArray(results));

     }

     /**

      * Return the registered Activity with the specified identifier, if any;

      * otherwise return <code>null</code>.

      *

      * @param id Identifier of the desired Activity

      */

     public Activity findActivity(String id) {

         return ((Activity) activities.get(id));

     }

     /**

      * Remove the specified Activity from this Registry.

      *

      * @param activity The Activity to be removed

      */

     public void removeActivity(Activity activity) {

         activities.remove(activity.getId());

     }

     // ------------------------------------------------------- Static Variables

     /**

      * The singleton registry instance.

      */

     protected static Registry registry = null;

     // --------------------------------------------------------- Static Methods

     /**

      * Factory method to return a Singleton (per class loader)

      * <code>Registry</code> instance.

      */

     public static Registry getRegistry() {

         if (registry == null)

             registry = new BaseRegistry();

         return (registry);

     }

 }