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
18 package org.apache.log4j.xml;
19
20 import org.apache.logging.log4j.Logger;
21 import org.apache.logging.log4j.status.StatusLogger;
22 import org.xml.sax.EntityResolver;
23 import org.xml.sax.InputSource;
24
25 import java.io.ByteArrayInputStream;
26 import java.io.InputStream;
27
28 /**
29 * An {@link EntityResolver} specifically designed to return
30 * <code>log4j.dtd</code> which is embedded within the log4j jar
31 * file.
32 */
33 public class Log4jEntityResolver implements EntityResolver {
34 private static final Logger LOGGER = StatusLogger.getLogger();
35 private static final String PUBLIC_ID = "-//APACHE//DTD LOG4J 1.2//EN";
36
37 public InputSource resolveEntity(String publicId, String systemId) {
38 if (systemId.endsWith("log4j.dtd") || PUBLIC_ID.equals(publicId)) {
39 Class clazz = getClass();
40 InputStream in = clazz.getResourceAsStream("/org/apache/log4j/xml/log4j.dtd");
41 if (in == null) {
42 LOGGER.warn("Could not find [log4j.dtd] using [{}] class loader, parsed without DTD.",
43 clazz.getClassLoader());
44 in = new ByteArrayInputStream(new byte[0]);
45 }
46 return new InputSource(in);
47 } else {
48 return null;
49 }
50 }
51 }