/*

  * 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.configuration.resolver;

 import java.io.IOException;

 import java.io.InputStream;

 import java.net.URL;

 import java.net.URLConnection;

 import java.util.HashMap;

 import java.util.Map;

 import org.xml.sax.EntityResolver;

 import org.xml.sax.InputSource;

 import org.xml.sax.SAXException;

 /**

  * The DefaultEntityResolver used by XML Configurations.

  * @author <a

  * href="http://commons.apache.org/configuration/team-list.html">Commons

  * Configuration team</a>

  * @since 1.7

  * @version $Id: DefaultEntityResolver.java 1301991 2012-03-17 20:18:02Z sebb $

  */

 public class DefaultEntityResolver implements EntityResolver, EntityRegistry

 {

     /** Stores a map with the registered public IDs.*/

     private Map<String, URL> registeredEntities = new HashMap<String, URL>();

     /**

      * <p>

      * Registers the specified URL for the specified public identifier.

      * </p>

      * <p>

      * This implementation maps {@code PUBLICID}'s to URLs (from which

      * the resource will be loaded). A common use case for this method is to

      * register local URLs (possibly computed at runtime by a class loader) for

      * DTDs and Schemas. This allows the performance advantage of using a local

      * version without having to ensure every {@code SYSTEM} URI on every

      * processed XML document is local. This implementation provides only basic

      * functionality. If more sophisticated features are required, either calling

      * {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom

      * {@code DocumentBuilder} (which also can be initialized with a

      * custom {@code EntityResolver}) or creating a custom entity resolver

      * and registering it with the XMLConfiguration is recommended.

      * </p>

      *

      * @param publicId Public identifier of the Entity to be resolved

      * @param entityURL The URL to use for reading this Entity

      * @throws IllegalArgumentException if the public ID is undefined

      */

     public void registerEntityId(String publicId, URL entityURL)

     {

         if (publicId == null)

         {

             throw new IllegalArgumentException("Public ID must not be null!");

         }

         getRegisteredEntities().put(publicId, entityURL);

     }

     /**

      * Resolves the requested external entity. This is the default

      * implementation of the {@code EntityResolver} interface. It checks

      * the passed in public ID against the registered entity IDs and uses a

      * local URL if possible.

      *

      * @param publicId the public identifier of the entity being referenced

      * @param systemId the system identifier of the entity being referenced

      * @return an input source for the specified entity

      * @throws org.xml.sax.SAXException if a parsing exception occurs

      */

     public InputSource resolveEntity(String publicId, String systemId)

             throws SAXException

     {

         // Has this system identifier been registered?

         URL entityURL = null;

         if (publicId != null)

         {

             entityURL = getRegisteredEntities().get(publicId);

         }

         if (entityURL != null)

         {

             // Obtain an InputSource for this URL. This code is based on the

             // createInputSourceFromURL() method of Commons Digester.

             try

             {

                 URLConnection connection = entityURL.openConnection();

                 connection.setUseCaches(false);

                 InputStream stream = connection.getInputStream();

                 InputSource source = new InputSource(stream);

                 source.setSystemId(entityURL.toExternalForm());

                 return source;

             }

             catch (IOException e)

             {

                 throw new SAXException(e);

             }

         }

         else

         {

             // default processing behavior

             return null;

         }

     }

     /**

      * Returns a map with the entity IDs that have been registered using the

      * {@code registerEntityId()} method.

      *

      * @return a map with the registered entity IDs

      */

     public Map<String, URL> getRegisteredEntities()

     {

         return registeredEntities;

     }

 }