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The method of regularly creating and deleting logs based on Log4j 1. Background

Recently, to achieve the need to delete logs N days ago on a regular basis:

As a commonly used log generation tool, Log4j has a very limited strategy to clear logs. Automatic cleanup can only be achieved in RollingFileAppender by setting the MaxFileSize and maxBackupIndex properties to specify the size and number of log files to be retained.

But in actual production, our real demand is to generate a log file regularly every day, and then keep the log in recent days or months, and the historical log needs to be cleaned up in time. However, the DailyRollingFileAppender class in Log4j does not have attributes such as maxBackupIndex,maxFileSize, so it cannot be implemented through direct configuration.

In this case, you can write a script that deletes the log regularly, or you can reimplement the DailyRollingFileAppender class.

Here we re-implement the DailyRollingFileAppender class by inheriting FileAppender, with the ability to delete log files N days ago in chronological order.

two。 Specific implementation 2.1 code implementation

Package com.demo.filter

Import java.io.File

Import java.io.FilenameFilter

Import java.io.IOException

Importjava.io.InterruptedIOException

Import java.io.Serializable

Import java.net.URI

Importjava.text.SimpleDateFormat

Import java.util.ArrayList

Import java.util.Calendar

Import java.util.Collections

Import java.util.Date

Importjava.util.GregorianCalendar

Import java.util.List

Import java.util.Locale

Import java.util.TimeZone

Importorg.apache.log4j.FileAppender

Import org.apache.log4j.Layout

Importorg.apache.log4j.helpers.LogLog

Importorg.apache.log4j.spi.LoggingEvent

/ * *

*

* @ Project name: wupao-job

* @ Class name: CustomDailyRollingFileAppender

* @ Class description: DailyRollingFileAppender extendsFileAppender

* override the RollingFileAppender class

* implement the maxBackupIndex function to limit the number of log files (regularly delete log files more than N days ago)

* @ creator: wyait

* @ creation time: 2:40:38 on August 8, 2017

* @ version:1.0.0

, /

Public classCustomDailyRollingFileAppender extends FileAppender {

/ / initialization parameters

Staticfinal int TOP_OF_TROUBLE =-1

Staticfinal int TOP_OF_MINUTE = 0

Staticfinal int TOP_OF_HOUR = 1

Staticfinal int HALF_DAY = 2

Staticfinal int TOP_OF_DAY = 3

Staticfinal int TOP_OF_WEEK = 4

Staticfinal int TOP_OF_MONTH = 5

/ * *

* production log file suffix ("'. 'yyyy-MM-dd")

, /

PrivateString datePattern = "'. 'yyyy-MM-dd"

/ * *

* default: 1 log file

, /

Protectedint maxBackupIndex = 1

/ * *

* Save the log file name of the previous day = filename+ ("'. 'yyyy-MM-dd")

, /

PrivateString scheduledFilename

/ / The next time we estimate a rollover should occur.

Privatelong nextCheck = System.currentTimeMillis ()-1

Datenow = new Date ()

SimpleDateFormatsdf

RollingCalendarrc = new RollingCalendar ()

IntcheckPeriod = TOP_OF_TROUBLE

/ / The gmtTimeZone is used only in computeCheckPeriod () method.

Staticfinal TimeZone gmtTimeZone = TimeZone.getTimeZone ("GMT")

/ / No parameter construction

PublicCustomDailyRollingFileAppender () {

}

/ * * parametric construction

Instantiate aDailyRollingFileAppender and open the

File designated byfilename. The opened filename will

Become the ouput destination for thisappender.

, /

PublicCustomDailyRollingFileAppender (Layout layout, String filename

StringdatePattern) throws IOException {

Super (layout,filename, true)

This.datePattern= datePattern

ActivateOptions ()

}

Publicvoid setDatePattern (String pattern) {

DatePattern= pattern

}

Publicvoid setMaxBackupIndex (int maxBackups) {

This.maxBackupIndex= maxBackups

}

Publicint getMaxBackupIndex () {

ReturnmaxBackupIndex

}

PublicString getDatePattern () {

ReturndatePattern

}

@ Override

Publicvoid activateOptions () {

Super.activateOptions ()

If (datePattern! = null & & fileName! = null) {

Now.setTime (System.currentTimeMillis ())

Sdf= new SimpleDateFormat (datePattern)

Inttype = computeCheckPeriod ()

PrintPeriodicity (type)

Rc.setType (type)

Filefile = new File (fileName)

ScheduledFilename= fileName

+ sdf.format (new Date (file.lastModified ()

} else {

LogLog.error ("EitherFile or DatePattern options are not set for appender ["

+ name + "].")

}

}

VoidprintPeriodicity (int type) {

Switch (type) {

CaseTOP_OF_MINUTE:

LogLog.debug ("Appender [" + name + "] to be rolled every minute.")

Break

CaseTOP_OF_HOUR:

LogLog.debug ("Appender [" + name)

+ "] to be rolled on top of every hour.")

Break

CaseHALF_DAY:

LogLog.debug ("Appender [" + name)

+ "] to be rolled at midday and midnight.")

Break

CaseTOP_OF_DAY:

LogLog.debug ("Appender [" + name + "] to be rolled at midnight.")

Break

CaseTOP_OF_WEEK:

LogLog.debug ("Appender [" + name)

+ "] to be rolled at start of week.")

Break

CaseTOP_OF_MONTH:

LogLog.debug ("Appender [" + name)

+ "] to be rolled at start of every month.")

Break

Default:

LogLog.warn ("Unknownperiodicity 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).

IntcomputeCheckPeriod () {

RollingCalendarrollingCalendar = new RollingCalendar (gmtTimeZone

Locale.getDefault ()

/ / set sate to 1970-01-01 00:00:00 GMT

Dateepoch = new Date (0)

If (datePattern! = null) {

For (int I = TOP_OF_MINUTE; I = maxBackupIndex) {

Intindex = 0

Intdiff = files.size ()-(maxBackupIndex-1)

For (ModifiedTimeSortableFile file: files) {

If (index > = diff)

Break

File.delete ()

Index++

}

}

/ * Compute filename, but only if datePattern is specified * /

If (datePattern = = null) {

ErrorHandler.error ("MissingDatePattern option in rollOver ().")

Return

}

LogLog.debug ("maxBackupIndex=" + maxBackupIndex)

StringdatedFilename = 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 ()

Filetarget = new File (scheduledFilename)

If (target.exists ()) {

Target.delete ()

}

Filefile = new File (fileName)

Booleanresult = file.renameTo (target)

If (result) {

LogLog.debug (fileName+ "- >" + scheduledFilename)

} else {

LogLog.error ("Failedto rename [" + fileName + "] to ["

+ scheduledFilename + "].")

}

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

}

/ * *

* This method differentiatesDailyRollingFileAppender from its

* super class.

*

*

Before actually logging, thismethod will check whether it is

* time to do a rollover. If it is, it willschedule the next

* rollover time and then rollover.

* * /

@ Override

Protectedvoid subAppend (LoggingEvent event) {

Longn = 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)

}

/ * *

* get all files in the same project log directory

* This method searches list of log files

* based on the pattern given in the log4jconfiguration file

* and returns a collection

* @ returnList

, /

PrivateList getAllFiles () {

Listfiles = new ArrayList ()

FilenameFilterfilter = new FilenameFilter () {

/ / override the accept method to confirm whether it is the same project log file name prefix.

@ Override

Publicboolean accept (File dir, String name) {

StringdirectoryName = dir.getPath ()

LogLog.debug ("directoryname:" + directoryName)

Filefile = new File (fileName)

StringperentDirectory = file.getParent ()

If (perentDirectory! = null) {

/ / name=demo.log

/ / directoryName= / logs

/ / Direct fileName.substring (directoryName.length ()); localFile=/demo.log after cutting. , which causes name.startsWith (localFile) to always be false

/ / so solution: length + 1

StringlocalFile = fileName.substring (directoryName

.length () + 1)

Returnname.startsWith (localFile)

}

Returnname.startsWith (fileName)

}

}

Filefile = new File (fileName)

StringperentDirectory = file.getParent ()

If (file.exists ()) {

If (file.getParent ()) = = null) {

StringabsolutePath = file.getAbsolutePath ()

PerentDirectory= absolutePath.substring (0

AbsolutePath.lastIndexOf (fileName))

}

}

Filedir = new File (perentDirectory)

String [] names = dir.list (filter)

For (int I = 0; I

< names.length; i++) { files.add(newModifiedTimeSortableFile(dir +System.getProperty("file.separator") + names[i])); } returnfiles; } } /** 自定义file类，重写compareTo方法，比较文件的修改时间 * The ClassModifiedTimeSortableFile extends java.io.File class and * implements Comparable to sortfiles list based upon their modified date */ class ModifiedTimeSortableFileextends File implements Serializable, Comparable{ privatestatic final long serialVersionUID = 1373373728209668895L; publicModifiedTimeSortableFile(String parent, String child) { super(parent,child); //TODO Auto-generated constructor stub } publicModifiedTimeSortableFile(URI uri) { super(uri); //TODO Auto-generated constructor stub } publicModifiedTimeSortableFile(File parent, String child) { super(parent,child); } publicModifiedTimeSortableFile(String string) { super(string); } @Override publicint compareTo(File anotherPathName) { longthisVal = this.lastModified(); longanotherVal = anotherPathName.lastModified(); return(thisVal < anotherVal ? -1 : (thisVal == anotherVal ? 0 : 1)); } } /** * RollingCalendar is a helper class toDailyRollingFileAppender. * Given a periodicity type and the currenttime, it computes the * start of the next interval. * */ class RollingCalendar extendsGregorianCalendar { privatestatic final long serialVersionUID = -8295691444111406775L; inttype = CustomDailyRollingFileAppender.TOP_OF_TROUBLE; RollingCalendar(){ super(); } RollingCalendar(TimeZonetz, Locale locale) { super(tz,locale); } voidsetType(int type) { this.type= type; } publiclong getNextCheckMillis(Date now) { returngetNextCheckDate(now).getTime(); } publicDate getNextCheckDate(Date now) { this.setTime(now); switch(type) { caseCustomDailyRollingFileAppender.TOP_OF_MINUTE: this.set(Calendar.SECOND,0); this.set(Calendar.MILLISECOND,0); this.add(Calendar.MINUTE,1); break; caseCustomDailyRollingFileAppender.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; caseCustomDailyRollingFileAppender.HALF_DAY: this.set(Calendar.MINUTE,0); this.set(Calendar.SECOND,0); this.set(Calendar.MILLISECOND,0); inthour = 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; caseCustomDailyRollingFileAppender.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; caseCustomDailyRollingFileAppender.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; caseCustomDailyRollingFileAppender.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: thrownew IllegalStateException("Unknown periodicity type."); } returngetTime(); } } 2.2配置实现 在resources目录下，自定义log4j.xml日志配置文件： 2.3 测试类 main方法： public static voidmain1(String[] args) { finalFile file = new File("log4j.xml"); if(file.exists()) { finalURL url = Main.class.getClassLoader() .getResource("log4j.xml"); StringconfigFile = url.getPath(); PropertyConfigurator.configure("log4j.xml"); } log.trace("Trace"); log.debug("Debug"); log.info("Info"); log.warn("Warn"); log.error("Error"); log.fatal("Fatal"); } 第一次启动：

Manually create history files for several other dates:

The second startup:

2.4 actual combat configuration of project log4j

Log4j.rootLogger=INFO,demo

Log4j.logger.org.mybatis = INFO

Log4j.appender.demo=org.apache.log4j.ConsoleAppender

Log4j.appender.demo.layout=org.apache.log4j.PatternLayout

Log4j.appender.demo.layout.ConversionPattern=%m%n

Log4j.appender.demo=com.demo.filter.CustomDailyRollingFileAppender

# log4j.appender.demo=org.apache.log4j.RollingFileAppender

Log4j.appender.demo.File=D:/logs/demo.log

# log4j.appender.demo.Threshold=INFO

# log4j.appender.demo.ImmediateFlush=true

# log4j.appender.demo.Append=true

Log4j.appender.demo.maxBackupIndex=3

Log4j.appender.demo.layout.ConversionPattern= [% d {yyyy:MM:dd HH:mm:ss}]:% m\ r\ n

Log4j.appender.demoConsole.encoding=utf-8

Log4j.appender.demoConsole=org.apache.log4j.ConsoleAppender

Log4j.appender.demoConsole.Target= System.out

Log4j.appender.demoConsole.layout=org.apache.log4j.PatternLayout

Log4j.appender.demoConsole.layout.ConversionPattern= [% d {yyyy:MM:dd HH:mm:ss}]:% m\ r\ n

The meaning of 3.Log4j-related configuration

Log4j consists of three important components: the priority of log information, the output destination of log information, and the output format of log information. The priority of log information from high to low is ERROR, WARN, INFO and DEBUG, which are used to specify the importance of this log information; the output destination of the log information specifies whether the log will be printed to the console or to a file; and the output format controls the display of the log information. Log4j supports two configuration file formats, one in XML format and the other in Java property file (key = value). Here, we focus on XML-based configuration.

3.1 configure the root logger

The basic syntax is:

Where level is the priority of logging, divided into OFF, FATAL, ERROR, WARN, INFO, DEBUG, ALL, or your defined level. Log4j recommends using only four levels, and the priorities from highest to lowest are ERROR, WARN, INFO, and DEBUG.

Here, each appenderName is the name of the log information that needs to be configured below.

Practical examples:

Log4j.rootLogger=INFO,stdout, ROLLING_ERROR_FILE, ROLLING_INFO_FILE

3.2 configure log information output destination Appeder

The main types of Appender available in Log4j are as follows:

Org.apache.log4j.ConsoleAppender (console)

Org.apache.log4j.FileAppender (file)

Org.apache.log4j.DailyRollingFileAppender (generates a log file every day)

Org.apache.log4j.RollingFileAppender (generates a new file when the file size reaches the specified size)

Org.apache.log4j.WriterAppender (sends log information to any specified place in stream format)

The basic syntax is:

Practical examples:

Log4j.appender.ROLLING_ERROR_FILE=org.apache.log4j.DailyRollingFileAppender

There are also some differences in their attributes for different Appender. These attributes are mainly related to the naming rules, save paths and deletion strategies of log files.

3.2.1 attributes of ConsoleAppender

Threshold=WARN: specifies the lowest output level of log information, which defaults to DEBUG.

ImmediateFlush=true: indicates that all messages will be output immediately. If set to false, they will not be output. The default value is true.

Target=System.err: the default is System.out.

3.2.2 Properties of FileAppender

Threshold=WARN: specifies the lowest output level of log information, which defaults to DEBUG.

ImmediateFlush=true: indicates that all messages will be output immediately. If set to false, they will not be output. The default value is true.

Append=false:true means that the message is added to the specified file, and false overwrites the specified file content. The default value is true.

File=D:/logs/logging.log4j: specifies that the message is output to the logging.log4j file.

3.2.3 attributes of DailyRollingFileAppender

Threshold=WARN: specifies the lowest output level of log information, which defaults to DEBUG.

ImmediateFlush=true: indicates that all messages will be output immediately. If set to false, they will not be output. The default value is true.

Append=false:true means that the message is added to the specified file, and false overwrites the specified file content. The default value is true.

File=D:/logs/logging.log4j: specifies that the current message is output to the logging.log4j file.

DatePattern='.'yyyy-MM: scroll the log file once a month, that is, generate a new log file every month. The log file for the current month is called logging.log4j, and the log file for the previous month is called logging.log4j.yyyy-MM.

In addition, you can also specify to scroll log files by week, day, hour, score, and so on. The corresponding format is as follows:

1)'. Yyyy-MM: every month

2)'. Yyyy-ww: every week

3)'. Yyyy-MM-dd: every day

4) yyyy-MM-dd-a: twice a day

5)'. Yyyy-MM-dd-HH: per hour

6)'. Yyyy-MM-dd-HH-mm: per minute

3.2.4 Properties of RollingFileAppender

Threshold=WARN: specifies the lowest output level of log information, which defaults to DEBUG.

ImmediateFlush=true: indicates that all messages will be output immediately. If set to false, they will not be output. The default value is true.

Append=false:true means that the message is added to the specified file, and false overwrites the specified file content. The default value is true.

File=D:/logs/logging.log4j: specifies that the message is output to the logging.log4j file.

MaxFileSize=100KB: the suffix can be KB, MB, or GB. When the log file reaches that size, it scrolls automatically, moving the original content to the logging.log4j.1 file.

MaxBackupIndex=2: specify the maximum number of scrolling files that can be generated. For example, if set to 2, two scrolling files and one logging.log4j file for logging.log4j.1,logging.log4j.2 can be generated.

3.3 configure the format (layout) of log information layout

There are several types of layout provided by Log4j:

Org.apache.log4j.HTMLLayout (layout in HTML form)

Org.apache.log4j.PatternLayout (layout mode can be flexibly specified)

Org.apache.log4j.SimpleLayout (level containing log information and information string)

Org.apache.log4j.TTCCLayout (contains information about the time, thread, category, etc., when the log was generated)

Log4j formats the log information in a print format similar to the printf function in C language. The print parameters are as follows:

% m outputs the message specified in the code

% p output priority, i.e. DEBUG,INFO,WARN,ERROR,FATAL

% r output the number of milliseconds it took since the application was started to output the log information

% c outputs the category to which it belongs, which is usually the full name of the class

T outputs the name of the thread that generated the log event

% n outputs a carriage return newline character with "rn" for Windows platform and "n" for Unix platform

% d output the date or time of the log point in time. The default format is ISO8601, or you can specify the format after that, for example:% d {yyy MMM dd HH:mm:ss,SSS}. The output is similar: October 18, 2002, 22, 14, 10, 14, 28, 921.

% l outputs where the log event occurs, including the class name, the thread that occurred, and the number of lines in the code. For example: Testlog4.main (TestLog4.java:10)

The basic syntax is:

Practical examples:

Log4j.appender.ROLLING_ERROR_FILE.layout=org.apache.log4j.PatternLayout

Log4j.appender.ROLLING_ERROR_FILE.layout.ConversionPattern= [log]% d -%-4r [% t]% c% x% n%-5p -% m [% l]% n

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