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.configuration2.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 *
33 * @since 1.7
34 */
35 public class DefaultEntityResolver implements EntityResolver, EntityRegistry {
36 /** Stores a map with the registered public IDs. */
37 private final Map<String, URL> registeredEntities = new HashMap<>();
38
39 /**
40 * Gets a map with the entity IDs that have been registered using the {@code registerEntityId()} method.
41 *
42 * @return a map with the registered entity IDs
43 */
44 @Override
45 public Map<String, URL> getRegisteredEntities() {
46 return registeredEntities;
47 }
48
49 /**
50 * <p>
51 * Registers the specified URL for the specified public identifier.
52 * </p>
53 * <p>
54 * This implementation maps {@code PUBLICID}'s to URLs (from which the resource will be loaded). A common use case for
55 * this method is to register local URLs (possibly computed at runtime by a class loader) for DTDs and Schemas. This
56 * allows the performance advantage of using a local version without having to ensure every {@code SYSTEM} URI on every
57 * processed XML document is local. This implementation provides only basic functionality. If more sophisticated
58 * features are required, either calling {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom
59 * {@code DocumentBuilder} (which also can be initialized with a custom {@code EntityResolver}) or creating a custom
60 * entity resolver and registering it with the XMLConfiguration is recommended.
61 * </p>
62 *
63 * @param publicId Public identifier of the Entity to be resolved
64 * @param entityURL The URL to use for reading this Entity
65 * @throws IllegalArgumentException if the public ID is undefined
66 */
67 @Override
68 public void registerEntityId(final String publicId, final URL entityURL) {
69 if (publicId == null) {
70 throw new IllegalArgumentException("Public ID must not be null!");
71 }
72 getRegisteredEntities().put(publicId, entityURL);
73 }
74
75 /**
76 * Resolves the requested external entity. This is the default implementation of the {@code EntityResolver} interface.
77 * It checks the passed in public ID against the registered entity IDs and uses a local URL if possible.
78 *
79 * @param publicId the public identifier of the entity being referenced
80 * @param systemId the system identifier of the entity being referenced
81 * @return an input source for the specified entity
82 * @throws org.xml.sax.SAXException if a parsing exception occurs
83 */
84 @SuppressWarnings("resource") // The stream is managed by the InputSource returned by this method.
85 @Override
86 public InputSource resolveEntity(final String publicId, final String systemId) throws SAXException {
87 // Has this system identifier been registered?
88 URL entityURL = null;
89 if (publicId != null) {
90 entityURL = getRegisteredEntities().get(publicId);
91 }
92
93 if (entityURL != null) {
94 // Obtain an InputSource for this URL. This code is based on the
95 // createInputSourceFromURL() method of Commons Digester.
96 try {
97 final URLConnection connection = entityURL.openConnection();
98 connection.setUseCaches(false);
99 final InputStream stream = connection.getInputStream();
100 final InputSource source = new InputSource(stream);
101 source.setSystemId(entityURL.toExternalForm());
102 return source;
103 } catch (final IOException e) {
104 throw new SAXException(e);
105 }
106 }
107 // default processing behavior
108 return null;
109 }
110 }