具体代码实现如下：
package com.mytools.common.log4jext;
import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.io.Writer;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Layout;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.PatternLayout;
import org.apache.log4j.helpers.CountingQuietWriter;
import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;
/**
* log4j appender扩展<br>
* （1）按天并且只保留最近n天的 <br>
* （2）如果一天的文件过大，可以按配置的大小将一天的文件进行切分
*
* @author shaoqz
* @since 2016-6-13
*/
public class MyDailyRollingFileAppender extends FileAppender
{
// The code assumes that the following constants are in a increasing
// sequence.
static final int TOP_OF_TROUBLE = -1;
static final int TOP_OF_MINUTE = 0;
static final int TOP_OF_HOUR = 1;
static final int HALF_DAY = 2;
static final int TOP_OF_DAY = 3;
static final int TOP_OF_WEEK = 4;
static final int TOP_OF_MONTH = 5;
/**
* The gmtTimeZone is used only in computeCheckPeriod() method.
*/
public static final TimeZone gmtTimeZone = TimeZone.getTimeZone("GMT");
/**
* The default maximum file size is 10MB. , 10K for test
*/
protected long maxFileSize = 10 * 1024;
/**
* The date pattern. By default, the pattern is set to "'.'yyyy-MM-dd" meaning daily
* rollover.
*/
private String datePattern = "'.'yyyy-MM-dd";
/**
* There is one backup file by default.
*/
private int maxBackupIndex = 1;
/**
* The log file will be renamed to the value of the scheduledFilename variable when
* the next interval is entered. For example, if the rollover period is one hour, the
* log file will be renamed to the value of "scheduledFilename" at the beginning of
* the next hour. The precise time when a rollover occurs depends on logging activity.
*/
private String scheduledFilename;
/**
* The next time we estimate a rollover should occur.
*/
private long nextCheck = System.currentTimeMillis() - 1;
private Date now = new Date();
private SimpleDateFormat sdf;
private MyRollingCalendar rollingCalendar = new MyRollingCalendar();
public int checkPeriod = TOP_OF_TROUBLE;
/**
* The default constructor does nothing.
*/
public MyDailyRollingFileAppender()
{
}
/**
* Instantiate a <code>DailyRollingFileAppender</code> and open the file designated by
* <code>filename</code>. The opened filename will become the ouput destination for
* this appender.
*/
public MyDailyRollingFileAppender(Layout layout, String filename, String datePattern) throws IOException
{
super(layout, filename, true);
this.datePattern = datePattern;
activateOptions();
}
/**
* The <b>DatePattern</b> takes a string in the same format as expected by
* {@link SimpleDateFormat}. This options determines the rollover schedule.
*/
public void setDatePattern(String pattern)
{
datePattern = pattern;
}
/** Returns the value of the <b>DatePattern</b> option. */
public String getDatePattern()
{
return datePattern;
}
/**
* 设置日志文件最大备份数
* <p>
* The <b>MaxBackupIndex</b> option determines how many backup files are kept before
* the oldest is erased. This option takes a positive integer value. If set to zero,
* then there will be no backup files and the log file will be renamed to the value of
* the scheduledFilename variable when the next interval is entered.
*/
public void setMaxBackupIndex(int maxBackups)
{
this.maxBackupIndex = maxBackups;
}
/**
* 返回日志文件最大备份数
*/
public int getMaxBackupIndex()
{
return maxBackupIndex;
}
public void activateOptions()
{
super.activateOptions();
LogLog.debug("Max backup file kept: " + maxBackupIndex + ".");
if (datePattern != null && fileName != null)
{
now.setTime(System.currentTimeMillis());
sdf = new SimpleDateFormat(datePattern);
int type = computeCheckPeriod();
printPeriodicity(type);
rollingCalendar.setType(type);
File file = new File(fileName);
scheduledFilename = fileName + sdf.format(new Date(file.lastModified()));
}
else
{
LogLog.error("Either File or DatePattern options are not set for appender [" + name + "].");
}
}
void printPeriodicity(int type)
{
switch (type)
{
case TOP_OF_MINUTE:
LogLog.debug("Appender [[+name+]] to be rolled every minute.");
break;
case TOP_OF_HOUR:
LogLog.debug("Appender [" + name + "] to be rolled on top of every hour.");
break;
case HALF_DAY:
LogLog.debug("Appender [" + name + "] to be rolled at midday and midnight.");
break;
case TOP_OF_DAY:
LogLog.debug("Appender [" + name + "] to be rolled at midnight.");
break;
case TOP_OF_WEEK:
LogLog.debug("Appender [" + name + "] to be rolled at start of week.");
break;
case TOP_OF_MONTH:
LogLog.debug("Appender [" + name + "] to be rolled at start of every month.");
break;
default:
LogLog.warn("Unknown periodicity for appender [[+name+]].");
}
}
int computeCheckPeriod()
{
MyRollingCalendar rollingPastCalendar = new MyRollingCalendar(gmtTimeZone, Locale.ENGLISH);
// set sate to 1970-01-01 00:00:00 GMT
Date epoch = new Date(0);
if (datePattern == null)
{
return TOP_OF_TROUBLE;
}
for (int i = TOP_OF_MINUTE; i <= TOP_OF_MONTH; i++)
{
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(datePattern);
simpleDateFormat.setTimeZone(gmtTimeZone); // do all date formatting in
// GMT
String r0 = simpleDateFormat.format(epoch);
rollingPastCalendar.setType(i);
Date next = new Date(rollingPastCalendar.getNextCheckMillis(epoch));
String r1 = simpleDateFormat.format(next);
// System.out.println("Type = "+i+", r0 = "+r0+", r1 = "+r1);
if (r0 != null && r1 != null && !r0.equals(r1))
{
return i;
}
}
return TOP_OF_TROUBLE; // Deliberately head for trouble...
}
/**
* Rollover the current file to a new file.
*/
void rollOver() throws IOException
{
/* Compute filename, but only if datePattern is specified */
if (datePattern == null)
{
errorHandler.error("Missing DatePattern option in rollOver().");
return;
}
String datedFilename = fileName + sdf.format(now);
// It is too early to roll over because we are still within the
// bounds of the current interval. Rollover will occur once the
// next interval is reached.
if (scheduledFilename.equals(datedFilename))
{
return;
}
// close current file, and rename it to datedFilename
this.closeFile();
File target = new File(scheduledFilename);
if (target.exists())
{
target.delete();
}
File file = new File(fileName);
boolean result = file.renameTo(target);
if (result)
{
LogLog.debug(fileName + " -> " + scheduledFilename);
// If maxBackups <= 0, then there is no file renaming to be done.
if (maxBackupIndex > 0)
{
// Delete the oldest file, to keep system happy.
file = new File(fileName + dateBefore());
// 删除很久以前的历史log文件
deleteAncientFilesIfExists(file);
if (file.exists())
{
file.delete();
}
}
}
else
{
LogLog.error("Failed to rename [[+fileName+]] to [[+scheduledFilename+]].");
}
try
{
// This will also close the file. This is OK since multiple close operations
// are safe.
this.setFile(fileName, false, this.bufferedIO, this.bufferSize);
}
catch (IOException e)
{
errorHandler.error("setFile(" + fileName + ", false) call failed.");
}
scheduledFilename = datedFilename;
}
/**
* 删除很久以前没有删除的日志文件（如果存在的话）
*
* @param oldestFile
*/
private void deleteAncientFilesIfExists(final File oldestFile)
{
// 找出久远日志文件列表
File[] ancientfiles = oldestFile.getParentFile().listFiles(new FileFilter()
{
@Override
public boolean accept(File pathname)
{
if (pathname.getPath().replaceAll("\\\\", "/").startsWith(fileName.replaceAll("\\\\", "/"))
&& pathname.getName().compareTo(oldestFile.getName()) < 0)
{
return true;
}
else
{
return false;
}
}
});
// 删除久远日志文件列表
for (File ancientfile : ancientfiles)
{
// 如果文件比配置的最老日期还老的话，删掉
ancientfile.delete();
}
}
private String dateBefore()
{
String dataAnte = "";
if (datePattern != null)
{
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(datePattern);
dataAnte = simpleDateFormat
.format(new Date(rollingCalendar.getPastCheckMillis(new Date(), maxBackupIndex)));
}
return dataAnte;
}
/**
* This method differentiates DailyRollingFileAppender from its super class.
* <p>
* Before actually logging, this method will check whether it is time to do a
* rollover. If it is, it will schedule the next rollover time and then rollover.
*/
protected void subAppend(LoggingEvent event)
{
// 根据文件大小roll over
rollOverBySize();
// 根据时间roll over
rollOverByTime();
super.subAppend(event);
}
/**
* 根据文件大小roll over
*/
private void rollOverBySize()
{
long currentTimeMillis = System.currentTimeMillis();
now.setTime(currentTimeMillis);
if (fileName != null && qw != null)
{
long size = ((CountingQuietWriter) qw).getCount();
if (size >= maxFileSize)
{
// close current file, and rename it
this.closeFile();
String rollingFileName = fileName + sdf.format(now) + '.' + currentTimeMillis;
new File(fileName).renameTo(new File(rollingFileName));
try
{
// This will also close the file. This is OK since multiple close
// operations
// are safe.
this.setFile(fileName, false, this.bufferedIO, this.bufferSize);
}
catch (IOException e)
{
errorHandler.error("setFile(" + fileName + ", false) call failed.");
}
}
}
}
/**
* 根据时间roll over
*/
private void rollOverByTime()
{
long currentTime = System.currentTimeMillis();
if (currentTime < nextCheck)
{
return;
}
now.setTime(currentTime);
nextCheck = rollingCalendar.getNextCheckMillis(now);
try
{
rollOver();
}
catch (IOException ioe)
{
LogLog.error("rollOver() failed.", ioe);
}
}
@Override
public synchronized void setFile(String fileName, boolean append, boolean bufferedIO, int bufferSize)
throws IOException
{
super.setFile(fileName, append, this.bufferedIO, this.bufferSize);
if (append)
{
File f = new File(fileName);
((CountingQuietWriter) qw).setCount(f.length());
}
}
@Override
protected void setQWForFiles(Writer writer)
{
this.qw = new CountingQuietWriter(writer, errorHandler);
}
/**
* 测试方法
*/
public static void main(String args[])
{
String className = MyDailyRollingFileAppender.class.getName();
MyDailyRollingFileAppender myAppender = new MyDailyRollingFileAppender();
myAppender.setDatePattern("'.'yyyy-MM-dd-HH");
myAppender.setFile("E:/test/mylogApender/test.log");
myAppender.setMaxBackupIndex(3);
PatternLayout patternLayout = new PatternLayout("%d [%-5p]-[%t]-[%c{1}] (%F:%L) %m%n");
myAppender.setLayout(patternLayout);
System.out.println("getMaxBackupIndex():" + myAppender.getMaxBackupIndex());
myAppender.activateOptions();
for (int i = 0; i < 50000; i++)
{
myAppender.subAppend(new LoggingEvent(className, Logger.getLogger(className), Level.INFO,
"test,hello " + i, null));
try
{
Thread.sleep(100);
}
catch (InterruptedException ex)
{
ex.printStackTrace();
}
System.out.println("Fine attesa");
}
}
}
/**
* MyRollingCalendar is a helper class to DailyMaxRollingFileAppender. Given a periodicity
* type and the current time, it computes the past maxBackupIndex date.
*/
class MyRollingCalendar extends GregorianCalendar
{
private static final long serialVersionUID = 1L;
public static final int TOP_OF_TROUBLE = -1;
public static final int TOP_OF_MINUTE = 0;
public static final int TOP_OF_HOUR = 1;
public static final int HALF_DAY = 2;
public static final int TOP_OF_DAY = 3;
public static final int TOP_OF_WEEK = 4;
public static final int TOP_OF_MONTH = 5;
int type = TOP_OF_TROUBLE;
MyRollingCalendar()
{
super();
}
MyRollingCalendar(TimeZone tz, Locale locale)
{
super(tz, locale);
}
public long getPastCheckMillis(Date now, int maxBackupIndex)
{
return getPastDate(now, maxBackupIndex).getTime();
}
public Date getPastDate(Date now, int maxBackupIndex)
{
this.setTime(now);
switch (type)
{
case TOP_OF_MINUTE:
this.set(Calendar.MINUTE, this.get(Calendar.MINUTE) - maxBackupIndex);
break;
case TOP_OF_HOUR:
this.set(Calendar.HOUR_OF_DAY, this.get(Calendar.HOUR_OF_DAY) - maxBackupIndex);
break;
case HALF_DAY:
int hour = get(Calendar.HOUR_OF_DAY);
if (hour < 12)
{
this.set(Calendar.HOUR_OF_DAY, 12);
}
else
{
this.set(Calendar.HOUR_OF_DAY, 0);
}
this.set(Calendar.DAY_OF_MONTH, this.get(Calendar.DAY_OF_MONTH) - maxBackupIndex);
break;
case TOP_OF_DAY:
this.set(Calendar.DATE, this.get(Calendar.DATE) - maxBackupIndex);
break;
case TOP_OF_WEEK:
this.set(Calendar.DAY_OF_WEEK, getFirstDayOfWeek());
this.set(Calendar.WEEK_OF_YEAR, this.get(Calendar.WEEK_OF_YEAR) - maxBackupIndex);
break;
case TOP_OF_MONTH:
this.set(Calendar.MONTH, this.get(Calendar.MONTH) - maxBackupIndex);
break;
default:
throw new IllegalStateException("Unknown periodicity type.");
}
return this.getTime();
}
public long getNextCheckMillis(Date now)
{
return getNextCheckDate(now).getTime();
}
public Date getNextCheckDate(Date now)
{
this.setTime(now);
switch (type)
{
case TOP_OF_MINUTE:
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
this.add(Calendar.MINUTE, 1);
break;
case TOP_OF_HOUR:
this.set(Calendar.MINUTE, 0);
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
this.add(Calendar.HOUR_OF_DAY, 1);
break;
case HALF_DAY:
this.set(Calendar.MINUTE, 0);
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
int hour = get(Calendar.HOUR_OF_DAY);
if (hour < 12)
{
this.set(Calendar.HOUR_OF_DAY, 12);
}
else
{
this.set(Calendar.HOUR_OF_DAY, 0);
this.add(Calendar.DAY_OF_MONTH, 1);
}
break;
case TOP_OF_DAY:
this.set(Calendar.HOUR_OF_DAY, 0);
this.set(Calendar.MINUTE, 0);
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
this.add(Calendar.DATE, 1);
break;
case TOP_OF_WEEK:
this.set(Calendar.DAY_OF_WEEK, getFirstDayOfWeek());
this.set(Calendar.HOUR_OF_DAY, 0);
this.set(Calendar.MINUTE, 0);
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
this.add(Calendar.WEEK_OF_YEAR, 1);
break;
case TOP_OF_MONTH:
this.set(Calendar.DATE, 1);
this.set(Calendar.HOUR_OF_DAY, 0);
this.set(Calendar.MINUTE, 0);
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
this.add(Calendar.MONTH, 1);
break;
default:
throw new IllegalStateException("Unknown periodicity type.");
}
return getTime();
}
void setType(int type)
{
this.type = type;
}
}
使用时在appender配置的地方增加MaxBackupIndex配置即可。