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 */
017package org.apache.commons.configuration2.resolver;
018
019import java.io.IOException;
020import java.io.InputStream;
021import java.net.URL;
022import java.net.URLConnection;
023import java.util.HashMap;
024import java.util.Map;
025
026import org.xml.sax.EntityResolver;
027import org.xml.sax.InputSource;
028import org.xml.sax.SAXException;
029
030/**
031 * The DefaultEntityResolver used by XML Configurations.
032 * @author <a
033 * href="http://commons.apache.org/configuration/team-list.html">Commons
034 * Configuration team</a>
035 * @since 1.7
036 * @version $Id: DefaultEntityResolver.java 1790899 2017-04-10 21:56:46Z ggregory $
037 */
038public class DefaultEntityResolver implements EntityResolver, EntityRegistry
039{
040    /** Stores a map with the registered public IDs.*/
041    private final Map<String, URL> registeredEntities = new HashMap<>();
042
043    /**
044     * <p>
045     * Registers the specified URL for the specified public identifier.
046     * </p>
047     * <p>
048     * This implementation maps {@code PUBLICID}'s to URLs (from which
049     * the resource will be loaded). A common use case for this method is to
050     * register local URLs (possibly computed at runtime by a class loader) for
051     * DTDs and Schemas. This allows the performance advantage of using a local
052     * version without having to ensure every {@code SYSTEM} URI on every
053     * processed XML document is local. This implementation provides only basic
054     * functionality. If more sophisticated features are required, either calling
055     * {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom
056     * {@code DocumentBuilder} (which also can be initialized with a
057     * custom {@code EntityResolver}) or creating a custom entity resolver
058     * and registering it with the XMLConfiguration is recommended.
059     * </p>
060     *
061     * @param publicId Public identifier of the Entity to be resolved
062     * @param entityURL The URL to use for reading this Entity
063     * @throws IllegalArgumentException if the public ID is undefined
064     */
065    @Override
066    public void registerEntityId(String publicId, URL entityURL)
067    {
068        if (publicId == null)
069        {
070            throw new IllegalArgumentException("Public ID must not be null!");
071        }
072        getRegisteredEntities().put(publicId, entityURL);
073    }
074
075    /**
076     * Resolves the requested external entity. This is the default
077     * implementation of the {@code EntityResolver} interface. It checks
078     * the passed in public ID against the registered entity IDs and uses a
079     * local URL if possible.
080     *
081     * @param publicId the public identifier of the entity being referenced
082     * @param systemId the system identifier of the entity being referenced
083     * @return an input source for the specified entity
084     * @throws org.xml.sax.SAXException if a parsing exception occurs
085     */
086    @Override
087    public InputSource resolveEntity(String publicId, String systemId)
088            throws SAXException
089    {
090        // Has this system identifier been registered?
091        URL entityURL = null;
092        if (publicId != null)
093        {
094            entityURL = getRegisteredEntities().get(publicId);
095        }
096
097        if (entityURL != null)
098        {
099            // Obtain an InputSource for this URL. This code is based on the
100            // createInputSourceFromURL() method of Commons Digester.
101            try
102            {
103                URLConnection connection = entityURL.openConnection();
104                connection.setUseCaches(false);
105                InputStream stream = connection.getInputStream();
106                InputSource source = new InputSource(stream);
107                source.setSystemId(entityURL.toExternalForm());
108                return source;
109            }
110            catch (IOException e)
111            {
112                throw new SAXException(e);
113            }
114        }
115        else
116        {
117            // default processing behavior
118            return null;
119        }
120    }
121
122    /**
123     * Returns a map with the entity IDs that have been registered using the
124     * {@code registerEntityId()} method.
125     *
126     * @return a map with the registered entity IDs
127     */
128    @Override
129    public Map<String, URL> getRegisteredEntities()
130    {
131        return registeredEntities;
132    }
133}