/*

  * $Id: ResourcesFactoryBase.java 349025 2005-11-25 21:09:54Z niallp $

  * $Revision: 349025 $

  * $Date: 2005-11-25 21:09:54 +0000 (Fri, 25 Nov 2005) $

  *

  * ====================================================================

  *

  *  Copyright 2003-2005 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.resources.impl;

 import java.util.HashMap;

 import java.util.Iterator;

 import java.util.Map;

 import org.apache.commons.resources.Resources;

 import org.apache.commons.resources.ResourcesException;

 import org.apache.commons.resources.ResourcesFactory;

 /**

  * <p>Convenience base class for {@link ResourcesFactory} implementations.

  * This implementation caches the {@link Resources} instances returned by

  * a protected <code>createResources()</code> method, which must be implemented

  * by concrete subclasses.</p>

  *

  * @see org.apache.commons.resources.impl.JDBCResourcesFactory

  * @see org.apache.commons.resources.impl.PropertyResourcesFactory

  * @see org.apache.commons.resources.impl.ResourceBundleResourcesFactory

  * @see org.apache.commons.resources.impl.WebappResourcesFactoryBase

  * @see org.apache.commons.resources.impl.WebappPropertyResourcesFactory

  * @see org.apache.commons.resources.impl.WebappXMLResourcesFactory

  * @see org.apache.commons.resources.impl.XMLResourcesFactory

  */

 public abstract class ResourcesFactoryBase implements ResourcesFactory {

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

     /**

      * <p>The set of {@link Resources} instances previously created by

      * this {@link ResourcesFactory}, keyed by logical name.</p>

      */

     private Map resources = new HashMap();

     /**

      * <p>The <code>returnNull</code> property value that will be configured

      * on {@link Resources} instances created by this factory.</p>

      */

     private boolean returnNull = true;

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

     /**

      * <p>Return the <code>returnNull</code> property value that will be

      * configured on {@link Resources} instances created by this factory.</p>

      * @return 'true' if null is returned for invalid key values.

      */

     public boolean isReturnNull() {

         return (this.returnNull);

     }

     /**

      * <p>Set the <code>returnNull</code> property value that will be

      * configured on {@link Resources} instances created by this factory.</p>

      *

      * @param returnNull The new value to delegate

      */

     public void setReturnNull(boolean returnNull) {

         this.returnNull = returnNull;

     }

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

     /**

      * <p>Create (if necessary) and return a {@link Resources} instance

      * for the specified logical name, with a default configuration.

      * The default implementation of this method treats the name as the

      * configuration String as well, and calls the

      * <code>getResources(String,String)</code> method.

      *

      * @param name Logical name of the {@link Resources} instance to

      *  be returned

      * @return The resources instance.

      *

      * @exception ResourcesException if a {@link Resources} instance

      *  of the specified logical name cannot be returned.

      */

     public Resources getResources(String name) {

         return (getResources(name, name));

     }

     /**

      * <p>Create (if necessary) and return a {@link Resources} instance

      * for the specified logical name, with a configuration based on

      * the specified configuration String.</p>

      *

      * @param name Logical name of the {@link Resources} instance to

      *  be returned

      * @param config Configuration string for this resource (meaning

      *  is dependent upon the {@link ResourcesFactory} implementation

      *  being utilized), or <code>null</code> for the default

      *  configuration

      * @return The resources instance.

      *

      * @exception ResourcesException if a {@link Resources} instance

      *  of the specified logical name cannot be returned.

      */

     public Resources getResources(String name, String config) {

         synchronized (resources) {

             Resources instance = (Resources) resources.get(name);

             if (instance == null) {

                 instance = createResources(name, config);

                 resources.put(name, instance);

             }

             return (instance);

         }

     }

     /**

      * <p>Release any internal references to {@link Resources} instances

      * that have been returned previously, after calling the

      * <code>destroy()</code> method on each such instance.</p>

      *

      * @exception ResourcesException if a problem occurred while releasing

      */

     public void release() {

         synchronized (resources) {

             Iterator names = resources.keySet().iterator();

             while (names.hasNext()) {

                 String name = (String) names.next();

                 ((Resources) resources.get(name)).destroy();

             }

             resources.clear();

         }

     }

     // ------------------------------------------------------ Protected Methods

     /**

      * <p>Create and return a new {@link Resources} instance with the

      * specified logical name, after calling its <code>init()</code>

      * method and delegating the relevant properties.  Concrete

      * subclasses <strong>MUST</strong> implement this method.</p>

      *

      * @param name Logical name of the {@link Resources} instance to create

      * @param config Configuration string for this resource (if any)

      * @return The new Resources instance.

      *

      * @exception ResourcesException if a {@link Resources} instance

      *  of the specified logical name cannot be created.

      */

     protected abstract Resources createResources(String name, String config);

 }