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 */
017 package org.apache.commons.configuration.resolver;
018
019 import java.io.IOException;
020 import java.io.InputStream;
021 import java.net.URL;
022 import java.net.URLConnection;
023 import java.util.HashMap;
024 import java.util.Map;
025
026 import org.xml.sax.EntityResolver;
027 import org.xml.sax.InputSource;
028 import 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 1206579 2011-11-26 20:30:51Z oheger $
037 */
038 public class DefaultEntityResolver implements EntityResolver, EntityRegistry
039 {
040 /** Stores a map with the registered public IDs.*/
041 private Map<String, URL> registeredEntities = new HashMap<String, URL>();
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 public void registerEntityId(String publicId, URL entityURL)
066 {
067 if (publicId == null)
068 {
069 throw new IllegalArgumentException("Public ID must not be null!");
070 }
071 getRegisteredEntities().put(publicId, entityURL);
072 }
073
074 /**
075 * Resolves the requested external entity. This is the default
076 * implementation of the {@code EntityResolver} interface. It checks
077 * the passed in public ID against the registered entity IDs and uses a
078 * local URL if possible.
079 *
080 * @param publicId the public identifier of the entity being referenced
081 * @param systemId the system identifier of the entity being referenced
082 * @return an input source for the specified entity
083 * @throws org.xml.sax.SAXException if a parsing exception occurs
084 */
085 public InputSource resolveEntity(String publicId, String systemId)
086 throws SAXException
087 {
088 // Has this system identifier been registered?
089 URL entityURL = null;
090 if (publicId != null)
091 {
092 entityURL = (URL) getRegisteredEntities().get(publicId);
093 }
094
095 if (entityURL != null)
096 {
097 // Obtain an InputSource for this URL. This code is based on the
098 // createInputSourceFromURL() method of Commons Digester.
099 try
100 {
101 URLConnection connection = entityURL.openConnection();
102 connection.setUseCaches(false);
103 InputStream stream = connection.getInputStream();
104 InputSource source = new InputSource(stream);
105 source.setSystemId(entityURL.toExternalForm());
106 return source;
107 }
108 catch (IOException e)
109 {
110 throw new SAXException(e);
111 }
112 }
113 else
114 {
115 // default processing behavior
116 return null;
117 }
118 }
119
120 /**
121 * Returns a map with the entity IDs that have been registered using the
122 * {@code registerEntityId()} method.
123 *
124 * @return a map with the registered entity IDs
125 */
126 public Map<String, URL> getRegisteredEntities()
127 {
128 return registeredEntities;
129 }
130 }