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/chainsaw/XMLFileHandler.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.chainsaw;

import java.util.StringTokenizer;
import org.apache.log4j.Level;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * A content handler for document containing Log4J events logged using the
 * XMLLayout class. It will create events and add them to a supplied model.
 *
 * @author <a href="mailto:oliver@puppycrawl.com">Oliver Burn</a>
 * @version 1.0
 */
class XMLFileHandler
    extends DefaultHandler
{
    /** represents the event tag **/
    private static final String TAG_EVENT = "log4j:event";
    /** represents the message tag **/
    private static final String TAG_MESSAGE = "log4j:message";
    /** represents the ndc tag **/
    private static final String TAG_NDC = "log4j:NDC";
    /** represents the throwable tag **/
    private static final String TAG_THROWABLE = "log4j:throwable";
    /** represents the location info tag **/
    private static final String TAG_LOCATION_INFO = "log4j:locationInfo";

    /** where to put the events **/
    private final MyTableModel mModel;
    /** the number of events in the document **/
    private int mNumEvents;

    /** the time of the event **/
    private long mTimeStamp;
    /** the priority (level) of the event **/
    private Level mLevel;
    /** the category of the event **/
    private String mCategoryName;
    /** the NDC for the event **/
    private String mNDC;
    /** the thread for the event **/
    private String mThreadName;
    /** the msg for the event **/
    private String mMessage;
    /** the throwable details the event **/
    private String[] mThrowableStrRep;
    /** the location details for the event **/
    private String mLocationDetails;
    /** buffer for collecting text **/
    private final StringBuffer mBuf = new StringBuffer();

    /**
     * Creates a new <code>XMLFileHandler</code> instance.
     *
     * @param aModel where to add the events
     */
    XMLFileHandler(MyTableModel aModel) {
        mModel = aModel;
    }

    /** @see DefaultHandler **/
    public void startDocument()
        throws SAXException
    {
        mNumEvents = 0;
    }

    /** @see DefaultHandler **/
    public void characters(char[] aChars, int aStart, int aLength) {
        mBuf.append(String.valueOf(aChars, aStart, aLength));
    }

    /** @see DefaultHandler **/
    public void endElement(String aNamespaceURI,
                           String aLocalName,
                           String aQName)
    {
        if (TAG_EVENT.equals(aQName)) {
            addEvent();
            resetData();
        } else if (TAG_NDC.equals(aQName)) {
            mNDC = mBuf.toString();
        } else if (TAG_MESSAGE.equals(aQName)) {
            mMessage = mBuf.toString();
        } else if (TAG_THROWABLE.equals(aQName)) {
            final StringTokenizer st =
                new StringTokenizer(mBuf.toString(), "\n\t");
            mThrowableStrRep = new String[st.countTokens()];
            if (mThrowableStrRep.length > 0) {
                mThrowableStrRep[0] = st.nextToken();
                for (int i = 1; i < mThrowableStrRep.length; i++) {
                    mThrowableStrRep[i] = "\t" + st.nextToken();
                }
            }
        }
    }

    /** @see DefaultHandler **/
    public void startElement(String aNamespaceURI,
                             String aLocalName,
                             String aQName,
                             Attributes aAtts)
    {
        mBuf.setLength(0);

        if (TAG_EVENT.equals(aQName)) {
            mThreadName = aAtts.getValue("thread");
            mTimeStamp = Long.parseLong(aAtts.getValue("timestamp"));
            mCategoryName = aAtts.getValue("logger");
            mLevel = Level.toLevel(aAtts.getValue("level"));
        } else if (TAG_LOCATION_INFO.equals(aQName)) {
            mLocationDetails = aAtts.getValue("class") + "."
                + aAtts.getValue("method")
                + "(" + aAtts.getValue("file") + ":" + aAtts.getValue("line")
                + ")";
        }
    }

    /** @return the number of events in the document **/
    int getNumEvents() {
        return mNumEvents;
    }

    ////////////////////////////////////////////////////////////////////////////
    // Private methods
    ////////////////////////////////////////////////////////////////////////////

    /** Add an event to the model **/
    private void addEvent() {
        mModel.addEvent(new EventDetails(mTimeStamp,
                                         mLevel,
                                         mCategoryName,
                                         mNDC,
                                         mThreadName,
                                         mMessage,
                                         mThrowableStrRep,
                                         mLocationDetails));
        mNumEvents++;
    }

    /** Reset the data for an event **/
    private void resetData() {
        mTimeStamp = 0;
        mLevel = null;
        mCategoryName = null;
        mNDC = null;
        mThreadName = null;
        mMessage = null;
        mThrowableStrRep = null;
        mLocationDetails = null;
    }
}

⏎ org/apache/log4j/chainsaw/XMLFileHandler.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

⇑⇑ FAQ for Apache Log4j