Apache Log4j provides the interface that applications should code to and provides the adapter components required for implementers to create a logging implementation.

Bytecode (Java 1.4) for Apache Log4j is provided in a JAR file like log4j-1.2.17.jar.

Source Code files for Apache Log4j are provided in both binary packge like log4j-1.2.17.zip and source package like log4j-1.2.17-sources.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j 1.2.17 below.

⏎ org/apache/log4j/Appender.java

/*
 * 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;

import org.apache.log4j.spi.Filter;
import org.apache.log4j.spi.ErrorHandler;
import org.apache.log4j.spi.LoggingEvent;

/**
   Implement this interface for your own strategies for outputting log
   statements.

   @author Ceki Gülcü 
*/
public interface Appender {

  /**
     Add a filter to the end of the filter list.

     @since 0.9.0
   */
  void addFilter(Filter newFilter);

  /**
     Returns the head Filter. The Filters are organized in a linked list
     and so all Filters on this Appender are available through the result.
     
     @return the head Filter or null, if no Filters are present
     @since 1.1
  */
  public
  Filter getFilter();

  /**
     Clear the list of filters by removing all the filters in it.
     
     @since 0.9.0
   */
  public
  void clearFilters();

  /**
     Release any resources allocated within the appender such as file
     handles, network connections, etc.

     <p>It is a programming error to append to a closed appender.

     @since 0.8.4
  */
  public
  void close();
  
  /**
     Log in <code>Appender</code> specific way. When appropriate,
     Loggers will call the <code>doAppend</code> method of appender
     implementations in order to log. */
  public
  void doAppend(LoggingEvent event);


  /**
     Get the name of this appender.
     @return name, may be null.*/
  public
  String getName();


  /**
     Set the {@link ErrorHandler} for this appender.

     @since 0.9.0
   */
  public
  void setErrorHandler(ErrorHandler errorHandler);

  /**
     Returns the {@link ErrorHandler} for this appender.

     @since 1.1
   */
  public
  ErrorHandler getErrorHandler();

  /**
     Set the {@link Layout} for this appender.

     @since 0.8.1
  */
  public
  void setLayout(Layout layout);

  /**
     Returns this appenders layout.
     
     @since 1.1
  */
  public
  Layout getLayout();
  

  /**
     Set the name of this appender. The name is used by other
     components to identify this appender.

     @since 0.8.1
  */
  public
  void setName(String name);

  /**
     Configurators call this method to determine if the appender
    requires a layout. If this method returns <code>true</code>,
    meaning that layout is required, then the configurator will
    configure an layout using the configuration information at its
    disposal.  If this method returns <code>false</code>, meaning that
    a layout is not required, then layout configuration will be
    skipped even if there is available layout configuration
    information at the disposal of the configurator..

     <p>In the rather exceptional case, where the appender
     implementation admits a layout but can also work without it, then
     the appender should return <code>true</code>.
     
     @since 0.8.4 */
  public
  boolean requiresLayout();
}

⏎ org/apache/log4j/Appender.java

Or download all of them as a single archive file:

File name: log4j-1.2.17-sources.jar
File size: 481200 bytes
Release date: 2012-05-06
Download 

⇒ Download and Install apache-log4j-1.2.15.zip

⇐ Download and Install log4j-1.2.17.zip

⇑ Downloading Apache Log4j 1.x JAR Packages

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