1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.configuration.resolver;
18
19 import java.io.IOException;
20 import java.io.InputStream;
21 import java.net.URL;
22 import java.net.URLConnection;
23 import java.util.HashMap;
24 import java.util.Map;
25
26 import org.xml.sax.EntityResolver;
27 import org.xml.sax.InputSource;
28 import org.xml.sax.SAXException;
29
30 /**
31 * The DefaultEntityResolver used by XML Configurations.
32 * @author <a
33 * href="http://commons.apache.org/configuration/team-list.html">Commons
34 * Configuration team</a>
35 * @since 1.7
36 * @version $Id: DefaultEntityResolver.java 1301991 2012-03-17 20:18:02Z sebb $
37 */
38 public class DefaultEntityResolver implements EntityResolver, EntityRegistry
39 {
40 /** Stores a map with the registered public IDs.*/
41 private Map<String, URL> registeredEntities = new HashMap<String, URL>();
42
43 /**
44 * <p>
45 * Registers the specified URL for the specified public identifier.
46 * </p>
47 * <p>
48 * This implementation maps {@code PUBLICID}'s to URLs (from which
49 * the resource will be loaded). A common use case for this method is to
50 * register local URLs (possibly computed at runtime by a class loader) for
51 * DTDs and Schemas. This allows the performance advantage of using a local
52 * version without having to ensure every {@code SYSTEM} URI on every
53 * processed XML document is local. This implementation provides only basic
54 * functionality. If more sophisticated features are required, either calling
55 * {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom
56 * {@code DocumentBuilder} (which also can be initialized with a
57 * custom {@code EntityResolver}) or creating a custom entity resolver
58 * and registering it with the XMLConfiguration is recommended.
59 * </p>
60 *
61 * @param publicId Public identifier of the Entity to be resolved
62 * @param entityURL The URL to use for reading this Entity
63 * @throws IllegalArgumentException if the public ID is undefined
64 */
65 public void registerEntityId(String publicId, URL entityURL)
66 {
67 if (publicId == null)
68 {
69 throw new IllegalArgumentException("Public ID must not be null!");
70 }
71 getRegisteredEntities().put(publicId, entityURL);
72 }
73
74 /**
75 * Resolves the requested external entity. This is the default
76 * implementation of the {@code EntityResolver} interface. It checks
77 * the passed in public ID against the registered entity IDs and uses a
78 * local URL if possible.
79 *
80 * @param publicId the public identifier of the entity being referenced
81 * @param systemId the system identifier of the entity being referenced
82 * @return an input source for the specified entity
83 * @throws org.xml.sax.SAXException if a parsing exception occurs
84 */
85 public InputSource resolveEntity(String publicId, String systemId)
86 throws SAXException
87 {
88 // Has this system identifier been registered?
89 URL entityURL = null;
90 if (publicId != null)
91 {
92 entityURL = getRegisteredEntities().get(publicId);
93 }
94
95 if (entityURL != null)
96 {
97 // Obtain an InputSource for this URL. This code is based on the
98 // createInputSourceFromURL() method of Commons Digester.
99 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 }