1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2026 the original author or authors.
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ///////////////////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle;
21
22 import java.io.IOException;
23 import java.io.InputStream;
24 import java.util.Map;
25
26 import javax.xml.parsers.ParserConfigurationException;
27 import javax.xml.parsers.SAXParserFactory;
28
29 import org.xml.sax.InputSource;
30 import org.xml.sax.SAXException;
31 import org.xml.sax.SAXParseException;
32 import org.xml.sax.XMLReader;
33 import org.xml.sax.helpers.DefaultHandler;
34
35 /**
36 * Contains the common implementation of a loader, for loading a configuration
37 * from an XML file.
38 *
39 * <p>
40 * The error handling policy can be described as being austere, dead set,
41 * disciplinary, dour, draconian, exacting, firm, forbidding, grim, hard, hard-
42 * boiled, harsh, harsh, in line, iron-fisted, no-nonsense, oppressive,
43 * persnickety, picky, prudish, punctilious, puritanical, rigid, rigorous,
44 * scrupulous, set, severe, square, stern, stickler, straight, strait-laced,
45 * stringent, stuffy, stuffy, tough, unpermissive, unsparing and uptight.
46 * </p>
47 *
48 * @noinspection ThisEscapedInObjectConstruction
49 * @noinspectionreason ThisEscapedInObjectConstruction - only reference is used and not
50 * accessed until initialized
51 */
52 public class XmlLoader
53 extends DefaultHandler {
54
55 /** Maps public id to resolve to resource name for the DTD. */
56 private final Map<String, String> publicIdToResourceNameMap;
57 /** Parser to read XML files. **/
58 private final XMLReader parser;
59
60 /**
61 * Creates a new instance.
62 *
63 * @param publicIdToResourceNameMap maps public IDs to DTD resource names
64 * @throws SAXException if an error occurs
65 * @throws ParserConfigurationException if an error occurs
66 */
67 protected XmlLoader(Map<String, String> publicIdToResourceNameMap)
68 throws SAXException, ParserConfigurationException {
69 this.publicIdToResourceNameMap = Map.copyOf(publicIdToResourceNameMap);
70 parser = createXmlReader(this);
71 }
72
73 /**
74 * Parses the specified input source.
75 *
76 * @param inputSource the input source to parse.
77 * @throws IOException if an error occurs
78 * @throws SAXException in an error occurs
79 */
80 public void parseInputSource(InputSource inputSource)
81 throws IOException, SAXException {
82 parser.parse(inputSource);
83 }
84
85 @Override
86 public InputSource resolveEntity(String publicId, String systemId) {
87 InputSource inputSource = null;
88 if (publicId != null) {
89 final String dtdResourceName = publicIdToResourceNameMap.get(publicId);
90
91 if (dtdResourceName != null) {
92 final ClassLoader loader = getClass().getClassLoader();
93 final InputStream dtdIs = loader.getResourceAsStream(dtdResourceName);
94 inputSource = new InputSource(dtdIs);
95 }
96 }
97 return inputSource;
98 }
99
100 @Override
101 public void error(SAXParseException exception) throws SAXException {
102 throw exception;
103 }
104
105 /**
106 * Helper method to create {@code XMLReader}.
107 *
108 * @param handler the content handler
109 * @return new XMLReader instance
110 * @throws ParserConfigurationException if a parser cannot be created
111 * @throws SAXException for SAX errors
112 */
113 private static XMLReader createXmlReader(DefaultHandler handler)
114 throws SAXException, ParserConfigurationException {
115 final SAXParserFactory factory = SAXParserFactory.newInstance();
116 LoadExternalDtdFeatureProvider.setFeaturesBySystemProperty(factory);
117 factory.setValidating(true);
118 final XMLReader xmlReader = factory.newSAXParser().getXMLReader();
119 xmlReader.setContentHandler(handler);
120 xmlReader.setEntityResolver(handler);
121 xmlReader.setErrorHandler(handler);
122 return xmlReader;
123 }
124
125 /**
126 * Used for setting specific for secure java installations features to SAXParserFactory.
127 * Pulled out as a separate class in order to suppress Pitest mutations.
128 */
129 public static final class LoadExternalDtdFeatureProvider {
130
131 /** System property name to enable external DTD load. */
132 public static final String ENABLE_EXTERNAL_DTD_LOAD = "checkstyle.enableExternalDtdLoad";
133
134 /** Feature that enables loading external DTD when loading XML files. */
135 public static final String LOAD_EXTERNAL_DTD =
136 "http://apache.org/xml/features/nonvalidating/load-external-dtd";
137 /** Feature that enables including external general entities in XML files. */
138 public static final String EXTERNAL_GENERAL_ENTITIES =
139 "http://xml.org/sax/features/external-general-entities";
140 /** Feature that enables including external parameter entities in XML files. */
141 public static final String EXTERNAL_PARAMETER_ENTITIES =
142 "http://xml.org/sax/features/external-parameter-entities";
143
144 /** Stop instances being created. **/
145 private LoadExternalDtdFeatureProvider() {
146 }
147
148 /**
149 * Configures SAXParserFactory with features required
150 * to use external DTD file loading, this is not activated by default to no allow
151 * usage of schema files that checkstyle do not know
152 * it is even security problem to allow files from outside.
153 *
154 * @param factory factory to be configured with special features
155 * @throws SAXException if an error occurs
156 * @throws ParserConfigurationException if an error occurs
157 */
158 public static void setFeaturesBySystemProperty(SAXParserFactory factory)
159 throws SAXException, ParserConfigurationException {
160
161 final boolean enableExternalDtdLoad = Boolean.parseBoolean(
162 System.getProperty(ENABLE_EXTERNAL_DTD_LOAD, "false"));
163
164 factory.setFeature(LOAD_EXTERNAL_DTD, enableExternalDtdLoad);
165 factory.setFeature(EXTERNAL_GENERAL_ENTITIES, enableExternalDtdLoad);
166 factory.setFeature(EXTERNAL_PARAMETER_ENTITIES, enableExternalDtdLoad);
167 }
168
169 }
170
171 }