Using log4j in Java projects

• log4j download

1. Official website: http://logging.apache.org/log4j/
2. log4j 1.2:http://logging.apache.org/log4j/1.2/download.html

• Use steps

1. Copy the log4j jar package to the project and add the build Path
2. Creating a configuration file Log4j.properties
3. Load the configuration file in the main function of the program: Propertyconfigurator.configure ("log4j.properties");
4. Create log instance: Logger log = Logger.getlogger (Xxx.class);
5. Log records: Log.debug ();

• Configuration file Example

# # # Set Log level # # #
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
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.E = Org.apache.log4j.DailyRollingFileAppender
Log4j.appender.e.file = Logs/error.log
Log4j.appender.e.append = True
Log4j.appender.e.threshold = ERROR
Log4j.appender.e.layout = Org.apache.log4j.PatternLayout
Log4j.appender.e.layout.conversionpattern =%-d{yyyy-mm-dd HH:mm:ss} [%t:%r]-[%p]%m%n

• Conversionpattern detailed

Format name meaning
The full name of the class to which the%c output log information belongs
%d the date or time of the output log time, the default format is ISO8601, or the format can be specified later, for example:%d{yyy-mm-dd HH:mm:ss}, output similar to: 2002-10-18-22:10:28
%f the class name of the class to which the output log information belongs
%l the occurrence of the output log event where the statement that outputs the log information is in the first line of the class it is in
%m the information specified in the output code, such as a message in log (message)
%n output a carriage return newline character, Windows platform is "RN", UNIX platform is "n"
%p output priority, or debug,info,warn,error,fatal. Debug if the debug () output is called, and so on
%r the number of milliseconds that the output from the application starts to output this log information
%t output The name of the thread that generated the log event

Using log4j in Java projects