Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.

⏎ org/apache/logging/log4j/core/appender/rolling/PatternProcessor.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.logging.log4j.core.appender.rolling;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.impl.Log4jLogEvent;
import org.apache.logging.log4j.core.lookup.StrSubstitutor;
import org.apache.logging.log4j.core.pattern.ArrayPatternConverter;
import org.apache.logging.log4j.core.pattern.DatePatternConverter;
import org.apache.logging.log4j.core.pattern.FormattingInfo;
import org.apache.logging.log4j.core.pattern.PatternConverter;
import org.apache.logging.log4j.core.pattern.PatternParser;
import org.apache.logging.log4j.status.StatusLogger;

/**
 * Parses the rollover pattern.
 */
public class PatternProcessor {

    protected static final Logger LOGGER = StatusLogger.getLogger();
    private static final String KEY = "FileConverter";

    private static final char YEAR_CHAR = 'y';
    private static final char MONTH_CHAR = 'M';
    private static final char[] WEEK_CHARS = {'w', 'W'};
    private static final char[] DAY_CHARS = {'D', 'd', 'F', 'E'};
    private static final char[] HOUR_CHARS = {'H', 'K', 'h', 'k'};
    private static final char MINUTE_CHAR = 'm';
    private static final char SECOND_CHAR = 's';
    private static final char MILLIS_CHAR = 'S';

    private final ArrayPatternConverter[] patternConverters;
    private final FormattingInfo[] patternFields;
    private final FileExtension fileExtension;

    private long prevFileTime = 0;
    private long nextFileTime = 0;
    private long currentFileTime = 0;

    private boolean isTimeBased = false;

    private RolloverFrequency frequency = null;

    private final String pattern;

    public String getPattern() {
        return pattern;
    }

    @Override
    public String toString() {
        return pattern;
    }

    /**
     * Constructor.
     * @param pattern The file pattern.
     */
    public PatternProcessor(final String pattern) {
        this.pattern = pattern;
        final PatternParser parser = createPatternParser();
        final List<PatternConverter> converters = new ArrayList<>();
        final List<FormattingInfo> fields = new ArrayList<>();
        parser.parse(pattern, converters, fields, false, false, false);
        final FormattingInfo[] infoArray = new FormattingInfo[fields.size()];
        patternFields = fields.toArray(infoArray);
        final ArrayPatternConverter[] converterArray = new ArrayPatternConverter[converters.size()];
        patternConverters = converters.toArray(converterArray);
        this.fileExtension = FileExtension.lookupForFile(pattern);

        for (final ArrayPatternConverter converter : patternConverters) {
            if (converter instanceof DatePatternConverter) {
                final DatePatternConverter dateConverter = (DatePatternConverter) converter;
                frequency = calculateFrequency(dateConverter.getPattern());
            }
        }
    }

    /**
     * Copy constructor with another pattern as source.
     *
     * @param pattern  The file pattern.
     * @param copy Source pattern processor
     */
    public PatternProcessor(final String pattern, final PatternProcessor copy) {
        this(pattern);
        this.prevFileTime = copy.prevFileTime;
        this.nextFileTime = copy.nextFileTime;
        this.currentFileTime = copy.currentFileTime;
    }

    public void setTimeBased(boolean isTimeBased) {
        this.isTimeBased = isTimeBased;
    }

    public long getCurrentFileTime() {
        return currentFileTime;
    }

    public void setCurrentFileTime(final long currentFileTime) {
        this.currentFileTime = currentFileTime;
    }

    public long getPrevFileTime() {
        return prevFileTime;
    }

    public void setPrevFileTime(final long prevFileTime) {
        LOGGER.debug("Setting prev file time to {}", new Date(prevFileTime));
        this.prevFileTime = prevFileTime;
    }

    public FileExtension getFileExtension() {
        return fileExtension;
    }

    /**
     * Returns the next potential rollover time.
     * @param currentMillis The current time.
     * @param increment The increment to the next time.
     * @param modulus If true the time will be rounded to occur on a boundary aligned with the increment.
     * @return the next potential rollover time and the timestamp for the target file.
     */
    public long getNextTime(final long currentMillis, final int increment, final boolean modulus) {
        //
        // https://issues.apache.org/jira/browse/LOG4J2-1232
        // Call setMinimalDaysInFirstWeek(7);
        //
        prevFileTime = nextFileTime;
        long nextTime;

        if (frequency == null) {
            throw new IllegalStateException("Pattern does not contain a date");
        }
        final Calendar currentCal = Calendar.getInstance();
        currentCal.setTimeInMillis(currentMillis);
        final Calendar cal = Calendar.getInstance();
        currentCal.setMinimalDaysInFirstWeek(7);
        cal.setMinimalDaysInFirstWeek(7);
        cal.set(currentCal.get(Calendar.YEAR), 0, 1, 0, 0, 0);
        cal.set(Calendar.MILLISECOND, 0);
        if (frequency == RolloverFrequency.ANNUALLY) {
            increment(cal, Calendar.YEAR, increment, modulus);
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.YEAR, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        cal.set(Calendar.MONTH, currentCal.get(Calendar.MONTH));
        if (frequency == RolloverFrequency.MONTHLY) {
            increment(cal, Calendar.MONTH, increment, modulus);
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.MONTH, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        if (frequency == RolloverFrequency.WEEKLY) {
            cal.set(Calendar.WEEK_OF_YEAR, currentCal.get(Calendar.WEEK_OF_YEAR));
            increment(cal, Calendar.WEEK_OF_YEAR, increment, modulus);
            cal.set(Calendar.DAY_OF_WEEK, currentCal.getFirstDayOfWeek());
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.WEEK_OF_YEAR, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        cal.set(Calendar.DAY_OF_YEAR, currentCal.get(Calendar.DAY_OF_YEAR));
        if (frequency == RolloverFrequency.DAILY) {
            increment(cal, Calendar.DAY_OF_YEAR, increment, modulus);
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.DAY_OF_YEAR, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        cal.set(Calendar.HOUR_OF_DAY, currentCal.get(Calendar.HOUR_OF_DAY));
        if (frequency == RolloverFrequency.HOURLY) {
            increment(cal, Calendar.HOUR_OF_DAY, increment, modulus);
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.HOUR_OF_DAY, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        cal.set(Calendar.MINUTE, currentCal.get(Calendar.MINUTE));
        if (frequency == RolloverFrequency.EVERY_MINUTE) {
            increment(cal, Calendar.MINUTE, increment, modulus);
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.MINUTE, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        cal.set(Calendar.SECOND, currentCal.get(Calendar.SECOND));
        if (frequency == RolloverFrequency.EVERY_SECOND) {
            increment(cal, Calendar.SECOND, increment, modulus);
            nextTime = cal.getTimeInMillis();
            cal.add(Calendar.SECOND, -1);
            nextFileTime = cal.getTimeInMillis();
            return debugGetNextTime(nextTime);
        }
        cal.set(Calendar.MILLISECOND, currentCal.get(Calendar.MILLISECOND));
        increment(cal, Calendar.MILLISECOND, increment, modulus);
        nextTime = cal.getTimeInMillis();
        cal.add(Calendar.MILLISECOND, -1);
        nextFileTime = cal.getTimeInMillis();
        return debugGetNextTime(nextTime);
    }

    public void updateTime() {
    	if (nextFileTime != 0 || !isTimeBased) {
			prevFileTime = nextFileTime;
            currentFileTime = 0;
		}
    }

    private long debugGetNextTime(final long nextTime) {
        if (LOGGER.isTraceEnabled()) {
            LOGGER.trace("PatternProcessor.getNextTime returning {}, nextFileTime={}, prevFileTime={}, current={}, freq={}", //
                    format(nextTime), format(nextFileTime), format(prevFileTime), format(System.currentTimeMillis()), frequency);
        }
        return nextTime;
    }

    private String format(final long time) {
        return new SimpleDateFormat("yyyy/MM/dd-HH:mm:ss.SSS").format(new Date(time));
    }

    private void increment(final Calendar cal, final int type, final int increment, final boolean modulate) {
        final int interval =  modulate ? increment - (cal.get(type) % increment) : increment;
        cal.add(type, interval);
    }

    /**
     * Format file name.
     * @param buf string buffer to which formatted file name is appended, may not be null.
     * @param obj object to be evaluated in formatting, may not be null.
     */
    public final void formatFileName(final StringBuilder buf, final boolean useCurrentTime, final Object obj) {
        long time = useCurrentTime ? currentFileTime : prevFileTime;
        if (time == 0) {
            time = System.currentTimeMillis();
        }
        formatFileName(buf, new Date(time), obj);
    }

    /**
     * Formats file name.
     * @param subst The StrSubstitutor.
     * @param buf string buffer to which formatted file name is appended, may not be null.
     * @param obj object to be evaluated in formatting, may not be null.
     */
    public final void formatFileName(final StrSubstitutor subst, final StringBuilder buf, final Object obj) {
        formatFileName(subst, buf, false, obj);
    }

    /**
     * Formats file name.
     * @param subst The StrSubstitutor.
     * @param buf string buffer to which formatted file name is appended, may not be null.
     * @param obj object to be evaluated in formatting, may not be null.
     */
    public final void formatFileName(final StrSubstitutor subst, final StringBuilder buf, final boolean useCurrentTime,
                                     final Object obj) {
        // LOG4J2-628: we deliberately use System time, not the log4j.Clock time
        // for creating the file name of rolled-over files.
        LOGGER.debug("Formatting file name. useCurrentTime={}. currentFileTime={}, prevFileTime={}",
            useCurrentTime, currentFileTime, prevFileTime);
        final long time = useCurrentTime ? currentFileTime != 0 ? currentFileTime : System.currentTimeMillis() :
                prevFileTime != 0 ? prevFileTime : System.currentTimeMillis();
        formatFileName(buf, new Date(time), obj);
        final LogEvent event = new Log4jLogEvent.Builder().setTimeMillis(time).build();
        final String fileName = subst.replace(event, buf);
        buf.setLength(0);
        buf.append(fileName);
    }

    /**
     * Formats file name.
     * @param buf string buffer to which formatted file name is appended, may not be null.
     * @param objects objects to be evaluated in formatting, may not be null.
     */
    protected final void formatFileName(final StringBuilder buf, final Object... objects) {
        for (int i = 0; i < patternConverters.length; i++) {
            final int fieldStart = buf.length();
            patternConverters[i].format(buf, objects);

            if (patternFields[i] != null) {
                patternFields[i].format(fieldStart, buf);
            }
        }
    }

    private RolloverFrequency calculateFrequency(final String pattern) {
        if (patternContains(pattern, MILLIS_CHAR)) {
            return RolloverFrequency.EVERY_MILLISECOND;
        }
        if (patternContains(pattern, SECOND_CHAR)) {
            return RolloverFrequency.EVERY_SECOND;
        }
        if (patternContains(pattern, MINUTE_CHAR)) {
            return RolloverFrequency.EVERY_MINUTE;
        }
        if (patternContains(pattern, HOUR_CHARS)) {
            return RolloverFrequency.HOURLY;
        }
        if (patternContains(pattern, DAY_CHARS)) {
            return RolloverFrequency.DAILY;
        }
        if (patternContains(pattern, WEEK_CHARS)) {
            return RolloverFrequency.WEEKLY;
        }
        if (patternContains(pattern, MONTH_CHAR)) {
            return RolloverFrequency.MONTHLY;
        }
        if (patternContains(pattern, YEAR_CHAR)) {
            return RolloverFrequency.ANNUALLY;
        }
        return null;
    }

    private PatternParser createPatternParser() {

        return new PatternParser(null, KEY, null);
    }

    private boolean patternContains(final String pattern, final char... chars) {
        for (final char character : chars) {
            if (patternContains(pattern, character)) {
                return true;
            }
        }
        return false;
    }

    private boolean patternContains(final String pattern, final char character) {
        return pattern.indexOf(character) >= 0;
    }

    public RolloverFrequency getFrequency() {
        return frequency;
    }

    public long getNextFileTime() {
        return nextFileTime;
    }

}

⏎ org/apache/logging/log4j/core/appender/rolling/PatternProcessor.java

Or download all of them as a single archive file:

File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06
Download 

⇒ Source Code for Apache Log4j JDK Logging Adapter

⇐ Source Code for Apache Log4j API

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j