Log4j中DailyRollingFileAppender日志文件清理策略

创作背景

log4j作为使用最广的日志框架，他的简单易用高效一直深受同行们的喜爱！但他的清理策略却十分缺乏，只有在RollingFileAppender中可以通过设置maxBackupIndex属性指定要保留的日志文件数的最大值来达到清理效果！

日志清理策略：[百度知道]

因开发需要，日志打印方式常常会采用DailyRollingFileAppender来实现按天打印或者按月打印等方式，而这种方式却是没有对应的清理策略的，这就需要重新实现DailyRollingFileAppender！

创作过程

创作之前必定会有一番疯狂的百度，毕竟只有站在前人的肩膀才能看得更远。然而在前人的创作成果并不能完全的满足需求的前提下 ，只能自己构思一个方案！

流程图如下：



依照流程图，主要修改了rollover()方法：

void rollOver() throws IOException {

if (datePattern == null) {
errorHandler.error("Missing DatePattern option in rollOver().");
return;
}

String datedFilename = fileName+sdf.format(now);

//如果最后一次的修改时间为当前时间 ，则不做任何任何操作
if (scheduledFilename.equals(datedFilename)) {
return;
}

// 关闭当前文件，重命名为日期文件
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);
} else {
LogLog.error("Failed to rename ["+fileName+"] to ["+scheduledFilename+"].");
}

//获取日志文件列表，控制数量，实现清理策略
if (file.getParentFile().exists()){
File[] files = file.getParentFile().listFiles(new LogFileFilter(file.getName()));
Long[] dateArray = new Long[files.length];
for (int i = 0; i < files.length; i++) {
File fileItem = files[i];
String fileDateStr = fileItem.getName().replace(file.getName(), "");
Date filedate = null;
try {
filedate = sdf.parse(fileDateStr);
long fileDateLong = filedate.getTime();
dateArray[i] = fileDateLong;
} catch (ParseException e) {
LogLog.error("Parse File Date Throw Exception : " + e.getMessage());
}
}
Arrays.sort(dateArray);
if (dateArray.length > maxBackupIndex) {
for (int i = 0; i < dateArray.length - maxBackupIndex; i++) {
String dateFileName = file.getPath() + sdf.format(dateArray[i]);
File dateFile = new File(dateFileName);
if (dateFile.exists()) {
dateFile.delete();
}
}
}
}

try {
// This will also close the file. This is OK since multiple close operations are safe.
this.setFile(fileName, true, this.bufferedIO, this.bufferSize);
}
catch(IOException e) {
errorHandler.error("setFile("+fileName+", true) call failed.");
}
scheduledFilename = datedFilename;
}

创作要点

新增参数maxBackupIndex，表示保留的文件数，默认值为1

直接使用DatePattern作为SimpleDateFormat的参数，这样可以完美支持DailyRollingFileAppender所支持的所有打印周期

实现FileFilter用于提高日志文件列表读取的效率

将日志文件（如“web.log.2016-01-12”）后缀的日期格式（如“2016-01-12”）转换成long类型进行排序，实现排序的准确性

转换成long类型时进行一场捕获：

try {
filedate = sdf.parse(fileDateStr);
long fileDateLong = filedate.getTime();
dateArray[i] = fileDateLong;
} catch (ParseException e) {
LogLog.error("Parse File Date Throw Exception : " + e.getMessage());
}

当日志列表中出现如“web.log.2016-01-12.bak”的情况时，可以忽略该文件！

6. 只在新建日志文件时运行清理策略，提高程序运行效率

附上代码

首先是重新实现的DailyRollingFileAppender源码：

package org.apache.log4j;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.io.InterruptedIOException;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.Locale;
import java.util.TimeZone;

import org.apache.log4j.helpers.LogLog;
import org.apache.log4j.spi.LoggingEvent;

/**
* 重写FileAppender类
* 让log4j在按日期分文件记录的基础上实现日志清理策略
*
* @author Mike.Peng
* @time Jan 12, 2016  5:29:01 PM
*/
public class MyDailyRollingFileAppender extends FileAppender {

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;

/**
* 默认设置："'.'yyyy-MM-dd"
* 设置说明：按天循环打印日志
*/
private String datePattern = "'.'yyyy-MM-dd";

private int  maxBackupIndex  = 1;

private String scheduledFilename;

/**
The next time we estimate a rollover should occur. */
private long nextCheck = System.currentTimeMillis () - 1;

Date now = new Date();

SimpleDateFormat sdf;

RollingCalendar rc = new RollingCalendar();

int checkPeriod = TOP_OF_TROUBLE;

/**
* 获取当前环境所处的时区
* 仅供computeCheckPeriod方法使用
*/
static final TimeZone gmtTimeZone = TimeZone.getTimeZone("GMT");

public MyDailyRollingFileAppender() {}

public MyDailyRollingFileAppender (Layout layout, String filename, String datePattern) throws IOException {
super(layout, filename, true);

this.datePattern = datePattern;
activateOptions();
}

public void setDatePattern(String pattern) {
this.datePattern = pattern;
}

public String getDatePattern() {
return datePattern;
}

public int getMaxBackupIndex() {
return maxBackupIndex;
}

public void setMaxBackupIndex(int maxBackupIndex) {
this.maxBackupIndex = maxBackupIndex;
}

/**
* activateOptions译名为激活操作
* 意思是按照配置的参数进行初始化
* scheduledFilename为log的最后一次修改时间
*/
@Override
public void activateOptions() {
super.activateOptions();

if(datePattern != null && fileName != null) {
now.setTime(System.currentTimeMillis());
sdf = new SimpleDateFormat(datePattern);
int type = computeCheckPeriod();
printPeriodicity(type);
rc.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+"].");
}
}

/**
* 根据type打印做出日志打印
* @param type
*/
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+"].");
}
}

//   This method computes the roll over period by looping over the
//   periods, starting with the shortest, and stopping when the r0 is
//   different from from r1, where r0 is the epoch formatted according
//   the datePattern (supplied by the user) and r1 is the
//   epoch+nextMillis(i) formatted according to datePattern. All date
//   formatting is done in GMT and not local format because the test
//   logic is based on comparisons relative to 1970-01-01 00:00:00
//   GMT (the epoch).

int computeCheckPeriod() {
RollingCalendar rollingCalendar = new RollingCalendar(gmtTimeZone, Locale.getDefault());
//设置初始时间为格林尼治时间：1970-01-01 00:00:00 GMT
Date epoch = new Date(0);
if(datePattern != null) {
for(int i = TOP_OF_MINUTE; i <= TOP_OF_MONTH; i++) {
//将所示的时间格式化为当前时区
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(datePattern);
simpleDateFormat.setTimeZone(gmtTimeZone);

String r0 = simpleDateFormat.format(epoch);
rollingCalendar.setType(i);
Date next = new Date(rollingCalendar.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...
}

/**
* 按照周期将当前日志文件转存为日期文件
*
* @throws IOException
*/
void rollOver() throws IOException {

if (datePattern == null) {
errorHandler.error("Missing DatePattern option in rollOver().");
return;
}

String datedFilename = fileName+sdf.format(now);

//如果最后一次的修改时间为当前时间 ，则不做任何任何操作
if (scheduledFilename.equals(datedFilename)) {
return;
}

// 关闭当前文件，重命名为日期文件
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);
} else {
LogLog.error("Failed to rename ["+fileName+"] to ["+scheduledFilename+"].");
}

//获取日志文件列表，控制数量，实现清理策略
if (file.getParentFile().exists()){
File[] files = file.getParentFile().listFiles(new LogFileFilter(file.getName()));
Long[] dateArray = new Long[files.length];
for (int i = 0; i < files.length; i++) {
File fileItem = files[i];
String fileDateStr = fileItem.getName().replace(file.getName(), "");
Date filedate = null;
try {
filedate = sdf.parse(fileDateStr);
long fileDateLong = filedate.getTime();
dateArray[i] = fileDateLong;
} catch (ParseException e) {
LogLog.error("Parse File Date Throw Exception : " + e.getMessage());
}
}
Arrays.sort(dateArray);
if (dateArray.length > maxBackupIndex) {
for (int i = 0; i < dateArray.length - maxBackupIndex; i++) {
String dateFileName = file.getPath() + sdf.format(dateArray[i]);
File dateFile = new File(dateFileName);
if (dateFile.exists()) {
dateFile.delete();
}
}
}
}

try {
// This will also close the file. This is OK since multiple close operations are safe.
this.setFile(fileName, true, this.bufferedIO, this.bufferSize);
}
catch(IOException e) {
errorHandler.error("setFile("+fileName+", true) call failed.");
}
scheduledFilename = datedFilename;
}

/**
* 写入日志之前判断是否需要新起一个日志来记录
*/
@Override
protected void subAppend(LoggingEvent event) {
long n = System.currentTimeMillis();
if (n >= nextCheck) {
now.setTime(n);
nextCheck = rc.getNextCheckMillis(now);
try {
rollOver();
} catch(IOException ioe) {
if (ioe instanceof InterruptedIOException) {
Thread.currentThread().interrupt();
}
LogLog.error("rollOver() failed.", ioe);
}
}
super.subAppend(event);
}
}

/**
* 文件过滤器
*
* @author Mike.Peng
* @time Jan 12, 2016  5:28:31 PM
*/
class LogFileFilter implements FileFilter {
private String logName;

public LogFileFilter(String logName) {
this.logName = logName;
}

@Override
public boolean accept(File file) {
if (logName == null || file.isDirectory()) {
return false;
} else {
LogLog.debug(file.getName());
return file.getName().startsWith(logName);
}
}
}

/**
* MyDailyRollingFileAppender的内部类
* 提供周期类型和当前时间 ，计算并返回下一个周期的开始时间
*
* @author Mike.Peng
* @time Jan 12, 2016  5:28:48 PM
*/
class RollingCalendar extends GregorianCalendar {
private static final long serialVersionUID = -3560331770601814177L;

int type = MyDailyRollingFileAppender.TOP_OF_TROUBLE;

/**
* RollingCalendar默认构造器
*/
RollingCalendar() {
super();
}

/**
* RollingCalendar构造器
* 根据地点时区 ，获取对应的日历Calendar
* @param tz
* @param locale
*/
RollingCalendar(TimeZone tz, Locale locale) {
super(tz, locale);
}

void setType(int type) {
this.type = type;
}

public long getNextCheckMillis(Date now) {
return getNextCheckDate(now).getTime();
}

/**
* 根据所传入的时间以及时间类型获取下一个时间
* @param now
* @return
*/
public Date getNextCheckDate(Date now) {
this.setTime(now);

switch(type) {
case MyDailyRollingFileAppender.TOP_OF_MINUTE:
this.set(Calendar.SECOND, 0);
this.set(Calendar.MILLISECOND, 0);
this.add(Calendar.MINUTE, 1);
break;
case MyDailyRollingFileAppender.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 MyDailyRollingFileAppender.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 MyDailyRollingFileAppender.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 MyDailyRollingFileAppender.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 MyDailyRollingFileAppender.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();
}
}

然后是log4j.properties文件的配置：

log4j.logger.TEST=debug,test

log4j.appender.test=org.apache.log4j.MyDailyRollingFileAppender
log4j.appender.test.File=${mike.web}/WEB-INF/logs/web.log
log4j.appender.test.DatePattern='.'yyyy-MM-dd
log4j.appender.test.layout=org.apache.log4j.PatternLayout
log4j.appender.test.layout.ConversionPattern=log4j.appender.test.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss.SSS} %C.%M(%F:%L) %n%p: %m%n
log4j.appender.test.maxBackupIndex=5
log4j.appender.test.encoding=UTF-8

最后是java代码中的使用方式：

private static Logger log = Logger.getLogger("TEST");
log.info("Log4j test !!!");

以上是针对DailyRollingFileAppender实现的文件清理策略，如有不足，请不吝赐教，在此谢过！

以上内容为作者原创，转载请注明出处，谢谢！