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    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.log4j.helpers.LogLog;
    21  import org.xml.sax.EntityResolver;
    22  import org.xml.sax.InputSource;
    23
    24  import java.io.InputStream;
    25  import java.io.ByteArrayInputStream;
    26
    27  /**
    28   * An {@link EntityResolver} specifically designed to return
    29   * <code>log4j.dtd</code> which is embedded within the log4j jar
    30   * file.
    31   *
    32   * @author Paul Austin
    33   * */
    34  public class Log4jEntityResolver implements EntityResolver {
    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  	    LogLog.warn("Could not find [log4j.dtd] using [" + clazz.getClassLoader()
    43  		     + "] class loader, parsed without DTD.");
    44          in = new ByteArrayInputStream(new byte[0]);
    45        }
    46  	  return new InputSource(in);
    47      } else {
    48        return null;
    49      }
    50    }
    51  }