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