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 * https://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
37 /** Stores a map with the registered public IDs. */
38 private final Map<String, URL> registeredEntities = new HashMap<>();
39
40 /**
41 * Constructs a new instance.
42 */
43 public DefaultEntityResolver() {
44 // empty
45 }
46
47 /**
48 * Gets a map with the entity IDs that have been registered using the {@code registerEntityId()} method.
49 *
50 * @return a map with the registered entity IDs
51 */
52 @Override
53 public Map<String, URL> getRegisteredEntities() {
54 return registeredEntities;
55 }
56
57 /**
58 * <p>
59 * Registers the specified URL for the specified public identifier.
60 * </p>
61 * <p>
62 * This implementation maps {@code PUBLICID}'s to URLs (from which the resource will be loaded). A common use case for
63 * this method is to register local URLs (possibly computed at runtime by a class loader) for DTDs and Schemas. This
64 * allows the performance advantage of using a local version without having to ensure every {@code SYSTEM} URI on every
65 * processed XML document is local. This implementation provides only basic functionality. If more sophisticated
66 * features are required, either calling {@code XMLConfiguration.setDocumentBuilder(DocumentBuilder)} to set a custom
67 * {@code DocumentBuilder} (which also can be initialized with a custom {@code EntityResolver}) or creating a custom
68 * entity resolver and registering it with the XMLConfiguration is recommended.
69 * </p>
70 *
71 * @param publicId Public identifier of the Entity to be resolved
72 * @param entityURL The URL to use for reading this Entity
73 * @throws IllegalArgumentException if the public ID is undefined
74 */
75 @Override
76 public void registerEntityId(final String publicId, final URL entityURL) {
77 if (publicId == null) {
78 throw new IllegalArgumentException("Public ID must not be null!");
79 }
80 getRegisteredEntities().put(publicId, entityURL);
81 }
82
83 /**
84 * Resolves the requested external entity. This is the default implementation of the {@code EntityResolver} interface.
85 * It checks the passed in public ID against the registered entity IDs and uses a local URL if possible.
86 *
87 * @param publicId the public identifier of the entity being referenced
88 * @param systemId the system identifier of the entity being referenced
89 * @return an input source for the specified entity
90 * @throws org.xml.sax.SAXException if a parsing exception occurs
91 */
92 @SuppressWarnings("resource") // The stream is managed by the InputSource returned by this method.
93 @Override
94 public InputSource resolveEntity(final String publicId, final String systemId) throws SAXException {
95 // Has this system identifier been registered?
96 URL entityURL = null;
97 if (publicId != null) {
98 entityURL = getRegisteredEntities().get(publicId);
99 }
100
101 if (entityURL != null) {
102 // Obtain an InputSource for this URL. This code is based on the
103 // createInputSourceFromURL() method of Commons Digester.
104 try {
105 final URLConnection connection = entityURL.openConnection();
106 connection.setUseCaches(false);
107 final InputStream stream = connection.getInputStream();
108 final InputSource source = new InputSource(stream);
109 source.setSystemId(entityURL.toExternalForm());
110 return source;
111 } catch (final IOException e) {
112 throw new SAXException(e);
113 }
114 }
115 // default processing behavior
116 return null;
117 }
118 }