How to configure a log4j file appender which rolls the log file every 15 minutes

Question

I understand that i can use a DailyRollingFileAppender to roll the log file every month, day, half-day, hour or minute. But how can i configure log4j to roll the log file ev

Answer 1

Here is code I use for Hourly. You can alter it for every 15 minutes - see method nextCalendar(). This code is based on DatedFileAppender.

package com.stackoverflow.log4j;

import java.io.File;
import java.util.Calendar;
import java.util.Date;

import org.apache.log4j.FileAppender;
import org.apache.log4j.spi.LoggingEvent;

/**
 * Based on biz.minaret.log4j.DatedFileAppender, 
 * decompiled with JAD,
 * revised to use optional hours.
 */
public class DistinctDailyFileAppender extends FileAppender {

public static final String DEFAULT_DIRECTORY = "logs";
public static final String DEFAULT_SUFFIX = ".txt";
public static final String DEFAULT_PREFIX = "";

private String directory = DEFAULT_DIRECTORY;
private String prefix = DEFAULT_PREFIX;
private String suffix = DEFAULT_SUFFIX;
private File currentPath = null;
private Calendar currentCalendar = null;
private long nextTime = 0l;
private boolean hourly = false;

/**
 * Constructor.
 */
public DistinctDailyFileAppender() {}

/**
 * This method is automatically called once by the system, 
 * immediately after all properties are set, prior to release.
 */
public void activateOptions() {

    currentPath = new File(directory);
    if (!currentPath.isAbsolute()) {        
        errorHandler.error("Directory failure for appender [" + name + "] : " + directory);
        return;
    }

    currentPath.mkdirs();

    // We can write; initialize calendar
    if (currentPath.canWrite()) {
        currentCalendar = Calendar.getInstance();
    } else {
        errorHandler.error("Cannot write for appender [" + name + "] : " + directory);
        return;
    }       
}

/**
 * This is called, synchronized by parent.
 */
public void append(LoggingEvent event) {

    if (layout == null) {
        errorHandler.error("No layout set for appender [" + name + "].");
        return;
    }

    if (currentCalendar == null) {
        errorHandler.error("Improper initialization for appender [" + name + "].");
        return;
    }

    long nowTime = System.currentTimeMillis();
    if (nowTime >= nextTime) {
        currentCalendar.setTime(new Date(nowTime));
        String timestamp = generateTimestamp(currentCalendar);
        nextCalendar(currentCalendar);
        nextTime = currentCalendar.getTime().getTime();
        File file = new File(currentPath, prefix + timestamp + suffix);
        fileName = file.getAbsolutePath();
        super.activateOptions();
    }

    if (super.qw == null) {

        errorHandler.error("No output stream or file set for the appender named [" + name + "].");
        return;

    } else {

        subAppend(event);
        return;

    }
}

protected String generateTimestamp(Calendar calendar) {

    int year = calendar.get(Calendar.YEAR);
    int month = calendar.get(Calendar.MONTH) + 1;
    int day = calendar.get(Calendar.DAY_OF_MONTH);
    int hour = calendar.get(Calendar.HOUR_OF_DAY);
    int minutes = calendar.get(Calendar.MINUTE);
    int seconds = calendar.get(Calendar.SECOND);

    StringBuffer buffer = new StringBuffer();

    if (year < 1000) {
        buffer.append('0');
        if (year < 100) {
            buffer.append('0');
            if (year < 10) {
                buffer.append('0');
            }
        }
    }
    buffer.append(Integer.toString(year));
    buffer.append('-');

    if (month < 10) {
        buffer.append('0');
    }
    buffer.append(Integer.toString(month));
    buffer.append('-');

    if (day < 10) {
        buffer.append('0');
    }
    buffer.append(Integer.toString(day));
    buffer.append('_');

    if (hour < 10) {
        buffer.append('0');
    }
    buffer.append(Integer.toString(hour));

    if (minutes < 10) {
        buffer.append('0');
    }
    buffer.append(Integer.toString(minutes));

    if (seconds < 10) {
        buffer.append('0');
    }
    buffer.append(Integer.toString(seconds));

    return buffer.toString();
}

protected void nextCalendar(Calendar calendar) {
    int i = calendar.get(Calendar.YEAR);
    int j = calendar.get(Calendar.MONTH);

    if (hourly) { 
        int k = calendar.get(Calendar.DAY_OF_MONTH);
        int l = calendar.get(Calendar.HOUR_OF_DAY) + 1;
        calendar.clear();
        calendar.set(i, j, k, l, 0);
    } else {
        int k = calendar.get(Calendar.DAY_OF_MONTH) + 1;
        calendar.clear();
        calendar.set(i, j, k);
    }
}

public String getDirectory() {
    return directory;
}

public void setDirectory(String directory) {
    if (directory == null || directory.length() == 0) {
        this.directory = "."; // Set to here
    } else {
        this.directory = directory;
    }
}

public String getPrefix() {
    return prefix;
}

public void setPrefix(String prefix) {
    if (prefix == null) {
        this.prefix = DEFAULT_PREFIX; // Set to default
    } else {
        this.prefix = prefix;
    }
}

public String getSuffix() {
    return suffix;
}

public void setSuffix(String suffix) {
    if (suffix == null) {
        this.suffix = ""; // Set to empty, not default
    } else {
        this.suffix = suffix;
    }
}

public void setHourly(boolean hourly) {
    this.hourly = hourly;
}

public boolean isHourly() {
    return this.hourly;
}
}

Here is my appender XML snippet: