log4j-Configuration file

The log4j configuration file is used to set the level, the repository, and the layout of the logger, which can be set in key=value format or in XML format.

By configuration, you can create a running environment for log4j.

1. The basic format of the configuration file log4j configuration file is as follows:

The code is as follows:

1 #配置根Logger2 3 Log4j.rootlogger = [level], appenderName1, appenderName2, ...4 
5 #配置日志信息输出目的地Appender6
7 log4j.appender.appenderName = Fully.qualified.name.of.appender.class8  
9 log4j.appender.appenderName.option1 = value1 ...10
  One Log4j.appender.appenderName.optionN = Valuen12
  - #配置日志信息的格式 (Layout)14
  the  log4j.appender.appenderName.layout = Fully.qualified.name.of.layout.class16
  -log4j.appender.appenderName.layout.option1 = value1 ...18
 +Log4j.appender.appenderName.layout.optionN = Valuen

Where [level] is the log output levels, there are 5 levels: The code is as follows:

1   FATAL 0  ERROR 3  WARN 4  INFO 6  DEBUG 7  

Appender for the log output destination, LOG4J provides the following types of Appender: The code is as follows:

1   Org.apache.log4j.ConsoleAppender (console), 2 3    org.apache.log4j.FileAppender (file),45    Org.apache.log4j.DailyRollingFileAppender (Generate a log file per day),67    Org.apache.log4j.RollingFileAppender (creates a new file when the file size reaches the specified size),89   Org.apache.log4j.WriterAppender (send log information in stream format to any specified location)

Layout: Log output format, LOG4J provides the following types of layout:

1   org.apache.log4j.HTMLLayout (Layout in HTML table Form), 2 3   Org.apache.log4j.PatternLayout (flexibility to specify layout mode), 4 5   Org.apache.log4j.SimpleLayout (contains the level of log information and the information string), 6 7   Org.apache.log4j.TTCCLayout (contains information about the time, thread, category, etc.) of the log

Printing parameters: log4j Format the log information in a print format similar to the printf function in C, as follows:

1  %m The message specified in the output code2 3 %p output priority, i.e. Debug,info,warn,error,fatal4 5 %r Output The number of milliseconds that the log information is consumed from the application boot to output6 7 %c output belongs to the class, which is usually the full name of the class8 9 %t Output The name of the thread that generated the log eventTen  One %n output A carriage return newline character, Windows platform is "\ r \ n", Unix platform is "\ n" A  - %d the date or time of the output log time, the default format is ISO8601, can also be specified after the format, such as:%d{yyy MMM dd HH:mm:ss, SSS}, output similar: October 18, 2002 22:10:28, 921 -  the%l where the output log event occurs, including the class name, the thread that occurred, and the number of rows in the code. Example: Testlog4.main (testlog4.java:10)

2. Initialize the logger in your code:

1) Call the Basicconfigurator.configure () method in the program: Add a consoleappender to the root logger, and the output format is set to "%-4r [%t]%-5p%c-%m%n" via Patternlayout, The default level of the root logger is level.debug.

2) configuration placed in the file, through the command line parameters to pass the file name, through Propertyconfigurator.configure (Args[x]) parsing and configuration;

3) The configuration is placed in the file, through the environment variables to pass the file name and other information, using the LOG4J default initialization process parsing and configuration;

4) configuration is placed in the file, through the application server configuration to pass the file name and other information, using a special servlet to complete the configuration.

3. Set the log output level for different Appender: When debugging a system, we tend to note only the exception level of log output, but usually all levels of output are placed in a file, if the level of log output is bug!?  Then go for it slowly. At this point we may think it would be nice to have the exception message output to a single file. Of course, LOG4J has provided such a function, we only need to modify the configuration of the Appender threshold can be implemented, such as the following example:

The configuration file code is as follows:

1 # # # set log Levels # # #2 3 Log4j.rootlogger = Debug, stdout, D, E4 5 # # # output to console # # #6 7 log4j.appender.stdout = Org.apache.log4j.ConsoleAppender8 9 log4j.appender.stdout.Target = System.outTen  One log4j.appender.stdout.layout = Org.apache.log4j.PatternLayout A  - Log4j.appender.stdout.layout.ConversionPattern =%d{absolute}%5p%c{1}:%l-%m%n -  the # # # Output to log file # # # -  - LOG4J.APPENDER.D = Org.apache.log4j.DailyRollingFileAppender -  + log4j.appender.d.file = Logs/log.log -  + Log4j.appender.d.append = True A  at log4j.appender.d.threshold = DEBUG -  - # # Output debug levels above the log -  - log4j.appender.d.layout = Org.apache.log4j.PatternLayout -  in Log4j.appender.d.layout.conversionpattern =%-d{yyyy-mm-dd HH:mm:ss} [%t:%r]-[%p]%m%n -  to # # # Save exception information to a separate file # # # +  - LOG4J.APPENDER.D = Org.apache.log4j.DailyRollingFileAppender the  * log4j.appender.d.file = Logs/error.log $ Panax Notoginseng # # Exception Log file name -  the Log4j.appender.d.append = True +  A log4j.appender.d.threshold = ERROR the  + # # Only output logs above the 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

1  Public classtestlog4j {2 3       Public Static voidMain (string[] args) {4 5Propertyconfigurator.configure ("D:/code/conf/log4j.properties" );6 7Logger Logger = Logger.getlogger (testlog4j.class );8  9Logger.debug ("Debug" );Ten    OneLogger.error ("Error" ); A  -      } -  the}

Run and see if the exception is stored in a separate file Error.log

log4j-Configuration file