+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.log4j.xml;
+
+import org.apache.log4j.helpers.LogLog;
+import org.xml.sax.EntityResolver;
+import org.xml.sax.InputSource;
+
+import java.io.InputStream;
+import java.io.ByteArrayInputStream;
+
+/**
+ * An {@link EntityResolver} specifically designed to return
+ * <code>log4j.dtd</code> which is embedded within the log4j jar
+ * file.
+ *
+ * @author Paul Austin
+ * */
+public class Log4jEntityResolver implements EntityResolver {
+ private static final String PUBLIC_ID = "-//APACHE//DTD LOG4J 1.2//EN";
+
+ public InputSource resolveEntity (String publicId, String systemId) {
+ if (systemId.endsWith("log4j.dtd") || PUBLIC_ID.equals(publicId)) {
+ Class clazz = getClass();
+ InputStream in = clazz.getResourceAsStream("/org/apache/log4j/xml/log4j.dtd");
+ if (in == null) {
+ LogLog.warn("Could not find [log4j.dtd] using [" + clazz.getClassLoader()
+ + "] class loader, parsed without DTD.");
+ in = new ByteArrayInputStream(new byte[0]);
+ }
+ return new InputSource(in);
+ } else {
+ return null;
+ }
+ }
+}