Log4J's configuration file (Configuration File) is used to set the level, storage and layout of the logger, it can accept key=value format setting or setting information in xml format. Through configuration, you can create a Log4J runtime environment.
1. Configuration
file The basic format of the Log4J configuration file is as follows: #Configure
the root Logger
log4j.rootLogger = [ level ] , appenderName1 , appenderName2 , … #Configure the
log information output destination Appender
log4j.appender.appenderName = fully.qualified.name.of.appender.class log4j.appender.appenderName.option1 = value1 … log4j.appender.appenderName.optionN = valueN
#Configure the format (layout) of the log information
log4j.appender.appenderName.layout = fully.qualified.name.of.layout.class log4j.appender.appenderName.layout.option1 = value1 … log4j.appender.appenderName.layout.optionN = valueN
Where [level] is the log output level, there are 5 levels:
FATAL 0 ERROR 3 WARN 4 INFO 6 DEBUG 7
Appender is the log output destination. The appenders provided by Log4j are as follows:
org.apache.log4j.ConsoleAppender (console),
org.apache.log4j.FileAppender (file),
org.apache.log4j.DailyRollingFileAppender (generates one every day ) log file),
org.apache.log4j.RollingFileAppender (generate a new file when the file size reaches the specified size),
org.apache.log4j.WriterAppender (send log information to any specified place in stream format)
Layout: log Output format, the layouts provided by Log4j are as follows:
org.apache.log4j.HTMLLayout (layout in HTML form),
org.apache.log4j.PatternLayout (layout mode can be flexibly specified),
org.apache.log4j.SimpleLayout (including the level and information string of log information),
org.apache.log4j.TTCCLayout (including log generation time, thread, category, etc.)
print parameters: Log4J uses a print format format similar to the printf function in C language The log information is as follows:
%m The message specified in the output code
%p The output priority, namely DEBUG, INFO, WARN, ERROR, FATAL
%r The number of milliseconds it takes to output the log information from the application startup to the output
%c Output the category to which it belongs, usually the full name of the class in which it belongs
%t Output the thread name that generated the log event
%n Output a carriage return and line feed, "/r/n" for Windows platforms, "/n" for Unix platforms ”
%d The date or time of the log time point, the default format is ISO8601, you can also specify the format after it, for example: %d{yyy MMM dd HH:mm:ss , SSS}, the output is similar to: October 18, 2002 Day 22:10:28, 921
%l Output where the log event occurred, including the category name, the thread in which it occurred, and the number of lines in the code. Example: Testlog4.main(TestLog4.java: 10 )
2. Initialize the Logger in the code:
1) Call the BasicConfigurator.configure() method in the program: add a ConsoleAppender to the root logger, and set the output format to "%- 4r [%t] %-5p %c %x - %m%n", and the default level of the root logger is Level.DEBUG.
2) The configuration is placed in a file, the file name is passed through the command line parameter, and the PropertyConfigurator .configure(args[x]) is parsed and configured;
3) The configuration is placed in a file, the file name and other information are passed through environment variables, and the default initialization process of log4j is used to parse and configure;
4) The configuration is placed in a file and passed through the application server The configuration passes information such as the file name, and uses a special servlet to complete the configuration.
3. Set the log output level for different Appenders:
When debugging the system, we often pay attention to the log output of abnormal level, but usually all levels of output are placed in a file, if the level of log output is BUG! ? Then go find it slowly.
At this time, we may wonder how good it would be to output the exception information to a file alone. Of course, Log4j already provides such a function, we only need to modify the Appender's Threshold in the configuration to achieve it, such as the following example:
[Configuration file]
### set log levels ###
log4j.rootLogger = debug , stdout , D , E
### Output to console ###
log4j.appender.stdout = org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target = System.out
log4j.appender.stdout.layout = org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern = %d{ABSOLUTE} %5p %c{ 1 }:%L - %m%n
### Output to log file ###
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
log4j.appender.D.File = logs/log.log
log4j.appender.D.Append = true
log4j.appender.D.Threshold = DEBUG ## Output logs above DEBUG level
log4j.appender.D.layout = org.apache.log4j.PatternLayout
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] - [ %p ] %m%n
### Save exception information to a separate file ###
log4j.appender.D = org.apache.log4j.DailyRollingFileAppender
log4j.appender.D.File = logs/error.log ## Exception log file name
log4j.appender.D.Append = true
log4j.appender.D.Threshold = ERROR ## Only output logs above ERROR level!!!
log4j.appender.D.layout = org.apache.log4j.PatternLayout
log4j.appender.D.layout.ConversionPattern = %-d{yyyy-MM-dd HH:mm:ss} [ %t:%r ] - [ %p ] %m%n
[used in code]
public class TestLog4j {
public static void main(String[] args) {
PropertyConfigurator.configure( " D:/Code/conf/log4j.properties " );
Logger logger = Logger.getLogger (TestLog4j. Class);
logger.debug( " debug " );
logger.error( " error " );
}
}
Run it to see if the exception information is saved in a separate file error.log
log4j.properties Use
1. Parameter meaning description
Type of output level
ERROR, WARN, INFO, DEBUG
ERROR is a serious error, mainly a program error
WARN It is a general warning, such as session loss.
INFO is the information to be displayed in general, such as login and logout
DEBUG is the debugging information of the program.
Configure log information output destination
log4j.appender.appenderName = fully.qualified.name.of.appender.class
1. org.apache.log4j.ConsoleAppender (console)
2.org.apache.log4j.FileAppender (file) 3.org.apache.log4j.DailyRollingFileAppender (
generates a log file daily)
4.org.apache.log4j.RollingFileAppender (file When the size reaches the specified size, a new file is generated)
5.org.apache.log4j.WriterAppender (send log information to any specified place in stream format)
configure the format of log information
log4j.appender.appenderName.layout = fully. qualified.name.of.layout.class
1.org.apache.log4j.HTMLLayout (layout in HTML form),
2.org.apache.log4j.PatternLayout (layout patterns can be flexibly specified ), 3.org.apache.log4j.SimpleLayout (
level of log information included ) and information string),
4.org.apache.log4j.TTCCLayout (contains log generation time, thread, category, etc.)
console option
Threshold=DEBUG: Specifies the lowest level of log message output.
ImmediateFlush=true: The default value is true, which means that all messages will be output immediately.
Target=System.err: By default: System.out, specifies the output console
FileAppender option
Threshold=DEBUF: specifies the lowest level of output for log messages.
ImmediateFlush=true: The default value is true, which means that all messages will be output immediately.
File=mylog.txt: Specifies that messages are output to the mylog.txt file.
Append=false: The default value is true, which means adding the message to the specified file, and false means overwriting the content of the specified file with the message.
RollingFileAppender option
Threshold=DEBUG: Specifies the minimum level of output of log messages.
ImmediateFlush=true: The default value is true, which means that all messages will be output immediately.
File=mylog.txt: Specifies that messages are output to the mylog.txt file.
Append=false: The default value is true, which means adding the message to the specified file, and false means overwriting the content of the specified file with the message.
MaxFileSize=100KB: The suffix can be KB, MB or GB. When the log file reaches this size, it will be automatically rolled, that is, the original content will be moved to the mylog.log.1 file.
MaxBackupIndex=2: Specifies the maximum number of rolling files that can be generated.
log4j.appender.A1.layout.ConversionPattern=%-4r %-5p %d{yyyy-MM-dd HH:mm:ssS} %c %m%n
The meaning of several symbols in the log information format:
-X Number: X information is left-aligned when outputting;
%p: The priority of output log information, that is, DEBUG, INFO, WARN, ERROR, FATAL,
%d: The date or time of the output log time point, the default format is ISO8601, or it can be used in its After specifying the format, for example: %d{yyy MMM dd HH:mm:ss,SSS}, the output is similar to: October 18, 2002 22:10:28, 921
%r: The output from the application startup to the output of the log information costs The number of milliseconds
%c: The category to which the log information belongs, usually the full name of the class in which it belongs
%t: The thread name that generates the log event is
output %l: The location where the log event occurs, equivalent to %C.%M( %F:%L), including the category name, the thread in which it occurred, and the number of lines in the code. Example: Testlog4.main (TestLog4.java:10)
%x: Output the NDC (Nested Diagnostic Context) associated with the current thread, especially used in multi-client multi-threaded applications like java servlets.
%%: output a "%" character
%F: output the name of the file where the log message is generated
%L: output the line number in the code
%m: output the message specified in the code, the specific log information generated
%n: output a Carriage return line feed, "/r/n" for Windows platform, "/n" for Unix platform Output log information line feed
You can add modifiers between % and pattern characters to control the minimum width, maximum width, and text size Alignment. Such as:
1)%20c: Specify the name of the output category. The minimum width is 20. If the name of the category is less than 20, it will be right-aligned by default.
2)%-20c: Specify the name of the output category. The minimum width is 20. If the name of the category is less than 20, the "-" sign specifies left alignment.
3)%.30c: Specify the name of the output category. The maximum width is 30. If the name of the category is greater than 30, the extra characters on the left will be truncated, but if it is less than 30, there will be no spaces.
4)%20.30c: If the name of the category is less than 20, it will be filled with spaces and right-aligned. If the name of the category is longer than 30 characters, it will be truncated from the output characters farther from the left.
2. File configuration Sample1
log4j.rootLogger=DEBUG,A1,R
# log4j.rootLogger = INFO, A1, R
# ConsoleAppender output
log4j.appender.A1=org.apache.log4j.ConsoleAppender
log4j.appender.A1.layout=org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%c]-[%p] %m%n
# File outputs one file a day, the output path can be customized, usually under the root path
log4j.appender.R = org.apache.log4j.DailyRollingFileAppender
log4j.appender.R.File=blog_log.txt
log4j.appender.R.MaxFileSize=500KB
log4j.appender.R.MaxBackupIndex=10
log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c] [%p] - %m%n
File Configuration
The Log4J configuration file given below in Sample2 implements a full set of functions such as outputting to the console, files, rolling back files, sending log emails, outputting to database log tables, and custom labels.
log4j.rootLogger=DEBUG,CONSOLE,A1,im
#DEBUG,CONSOLE,FILE,ROLLING_FILE,MAIL,DATABASE
log4j.addivity.org.apache = true
###################
# Console Appender
###################
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.Threshold=DEBUG
log4j.appender.CONSOLE.Target=System.out
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=[framework] %d - %c -%-4r [%t] %-5p %c %x - %m%n
#log4j.appender.CONSOLE.layout.ConversionPattern=[start]%d{DATE}[DATE]%n%p[PRIORITY]%n%x[NDC]%n%t[THREAD] n%c[CATEGORY]%n%m[MESSAGE]%n%n
#####################
# File Appender
#####################
log4j.appender.FILE=org.apache.log4j.FileAppender
log4j.appender.FILE.File=file.log
log4j.appender.FILE.Append=false
log4j.appender.FILE.layout=org.apache.log4j.PatternLayout
log4j.appender.FILE.layout.ConversionPattern=[framework] %d - %c -%-4r [%t] %-5p %c %x - %m%n
# Use this layout for LogFactor 5 analysis
########################
# Rolling File
########################
log4j.appender.ROLLING_FILE=org.apache.log4j.RollingFileAppender
log4j.appender.ROLLING_FILE.Threshold=ERROR
log4j.appender.ROLLING_FILE.File=rolling.log
log4j.appender.ROLLING_FILE.Append=true
log4j.appender.ROLLING_FILE.MaxFileSize=10KB
log4j.appender.ROLLING_FILE.MaxBackupIndex=1
log4j.appender.ROLLING_FILE.layout=org.apache.log4j.PatternLayout
log4j.appender.ROLLING_FILE.layout.ConversionPattern=[framework] %d - %c -%-4r [%t] %-5p %c %x - %m%n
####################
# Socket Appender
####################
log4j.appender.SOCKET=org.apache.log4j.RollingFileAppender
log4j.appender.SOCKET.RemoteHost=localhost
log4j.appender.SOCKET.Port=5001
log4j.appender.SOCKET.LocationInfo=true
# Set up for Log Facter 5
log4j.appender.SOCKET.layout=org.apache.log4j.PatternLayout
log4j.appender.SOCET.layout.ConversionPattern=[start]%d{DATE}[DATE]%n%p[PRIORITY]%n%x[NDC]%n%t[THREAD]%n%c[CATEGORY]%n%m[MESSAGE]%n%n
########################
# Log Factor 5 Appender
########################
log4j.appender.LF5_APPENDER=org.apache.log4j.lf5.LF5Appender
log4j.appender.LF5_APPENDER.MaxNumberOfRecords=2000
########################
# SMTP Appender
#######################
log4j.appender.MAIL=org.apache.log4j.net.SMTPAppender
log4j.appender.MAIL.Threshold=FATAL
log4j.appender.MAIL.BufferSize=10
[email protected]
log4j.appender.MAIL.SMTPHost=mail.hollycrm.com
log4j.appender.MAIL.Subject=Log4J Message
[email protected]
log4j.appender.MAIL.layout=org.apache.log4j.PatternLayout
log4j.appender.MAIL.layout.ConversionPattern=[framework] %d - %c -%-4r [%t] %-5p %c %x - %m%n
########################
# JDBC Appender
#######################
log4j.appender.DATABASE=org.apache.log4j.jdbc.JDBCAppender
log4j.appender.DATABASE.URL=jdbc:mysql://localhost:3306/test
log4j.appender.DATABASE.driver=com.mysql.jdbc.Driver
log4j.appender.DATABASE.user=root
log4j.appender.DATABASE.password=
log4j.appender.DATABASE.sql=INSERT INTO LOG4J (Message) VALUES ('[framework] %d - %c -%-4r [%t] %-5p %c %x - %m%n')
log4j.appender.DATABASE.layout=org.apache.log4j.PatternLayout
log4j.appender.DATABASE.layout.ConversionPattern=[framework] %d - %c -%-4r [%t] %-5p %c %x - %m%n
log4j.appender.A1 = org.apache.log4j.DailyRollingFileAppender
log4j.appender.A1.File=SampleMessages.log4j
log4j.appender.A1.DatePattern=yyyyMMdd-HH'.log4j'
log4j.appender.A1.layout=org.apache.log4j.xml.XMLLayout
###################
#customAppender
###################
log4j.appender.im = net.cybercorlin.util.logger.appender.IMAppender
log4j.appender.im.host = mail.cybercorlin.net
log4j.appender.im.username = username
log4j.appender.im.password = password
log4j.appender.im.recipient = [email protected]
log4j.appender.im.layout=org.apache.log4j.PatternLayout
log4j.appender.im.layout.ConversionPattern =[framework] %d - %c -%-4r [%t] %-5p %c
%x - %m%n
3. Advanced use
Experimental purpose:
1. Write FATAL level errors into the 2000NT log
2. WARN, ERROR, FATAL level errors send email to notify
the administrator 3. Other level errors are directly output in the background
Experimental steps :
Output to the 2000NT log
1. Copy NTEventLogAppender.dll in the Log4j archive to the WINNT/SYSTEM32 directory
2. Write the configuration file log4j.properties
# Output in the 2000 system log
log4j.logger.NTlog=FATAL, A8 # APPENDER A8 log4j.appender.A8=org.apache.log4j.nt.NTEventLogAppender log4j.appender.A8.Source = JavaTest log4j.appender.A8.layout=org.apache.log4j.PatternLayout log4j.appender.A8.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
3. Calling code:
Logger logger2 = Logger.getLogger("NTlog"); //It should be the same as the name set in the configuration file
logger2.debug("debug!!!");
logger2.info("info!!!");
logger2.warn("warn!!!");
logger2.error("error!!!");
//Only this error will be written to the 2000 log
logger2.fatal("fatal!!!");
Send email to notify administrator:
1. First download JavaMail and JAF,
http://java.sun.com/j2ee/ja/javamail/index.html http://java.sun.com/beans/glasgow/jaf.html
Reference mail.jar and activation.jar in the project.
2. Write configuration file
# Send logs to email
log4j.logger.MailLog=WARN,A5 # APPENDER A5 log4j.appender.A5=org.apache.log4j.net.SMTPAppender log4j.appender.A5.BufferSize=5 [email protected] [email protected] log4j.appender.A5.Subject=ErrorLog log4j.appender.A5.SMTPHost=smtp.263.net log4j.appender.A5.layout=org.apache.log4j.PatternLayout log4j.appender.A5.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
3. Calling code:
//Send the log to mail
Logger logger3 = Logger.getLogger("MailLog");
logger3.warn("warn!!!");
logger3.error("error!!!");
logger3.fatal("fatal!!!");
Output all categories of errors in the background:
1. Write the configuration file
# output in the background
log4j.logger.console=DEBUG, A1 # APPENDER A1 log4j.appender.A1=org.apache.log4j.ConsoleAppender log4j.appender.A1.layout=org.apache.log4j.PatternLayout log4j.appender.A1.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
2. calling code
Logger logger1 = Logger.getLogger("console");
logger1.debug("debug!!!");
logger1.info("info!!!");
logger1.warn("warn!!!");
logger1.error("error!!!");
logger1.fatal("fatal!!!");
-------------------------------------------------- ------------------
All configuration files: log4j.properties
# output in the background
log4j.logger.console=DEBUG, A1 # APPENDER A1 log4j.appender.A1=org.apache.log4j.ConsoleAppender log4j.appender.A1.layout=org.apache.log4j.PatternLayout log4j.appender.A1.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
# syslog output at 2000
log4j.logger.NTlog=FATAL, A8 # APPENDER A8 log4j.appender.A8=org.apache.log4j.nt.NTEventLogAppender log4j.appender.A8.Source = JavaTest log4j.appender.A8.layout=org.apache.log4j.PatternLayout log4j.appender.A8.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
# Send logs to email
log4j.logger.MailLog=WARN,A5 # APPENDER A5 log4j.appender.A5=org.apache.log4j.net.SMTPAppender log4j.appender.A5.BufferSize=5 [email protected] [email protected] log4j.appender.A5.Subject=ErrorLog log4j.appender.A5.SMTPHost=smtp.263.net log4j.appender.A5.layout=org.apache.log4j.PatternLayout log4j.appender.A5.layout.ConversionPattern=%-4r %-5p [%t] %37c %3x - %m%n
Full code: Log4jTest.java
/*
* Creation date 2003-11-13
*/
package edu.bcu.Bean;
import org.apache.log4j.*;
//import org.apache.log4j.nt.*;
//import org.apache.log4j.net.*;
/**
* @author yanxu
*/
public class Log4jTest
{
public static void main(String args[])
{
PropertyConfigurator.configure("log4j.properties");
// output in the background
Logger logger1 = Logger.getLogger("console");
logger1.debug("debug!!!");
logger1.info("info!!!");
logger1.warn("warn!!!");
logger1.error("error!!!");
logger1.fatal("fatal!!!");
// output in NT syslog
Logger logger2 = Logger.getLogger("NTlog");
//NTEventLogAppender nla = new NTEventLogAppender();
logger2.debug("debug!!!");
logger2.info("info!!!");
logger2.warn("warn!!!");
logger2.error("error!!!");
//Only this error will be written to the 2000 log
logger2.fatal("fatal!!!");
//Send the log to mail
Logger logger3 = Logger.getLogger("MailLog");
//SMTPAppender sa = new SMTPAppender();
logger3.warn("warn!!!");
logger3.error("error!!!");
logger3.fatal("fatal!!!");
}
}