log4j Log configuration file log4j.properties

# Specify level of log output, Destination: console, file
#  log output priority by root element: Debug < Info < Warn < error
Log4j.rootlogger=info,console, File
 
############# log output to console #############
# Log output to the console using the API class
log4j.appender.console= Org.apache.log4j.ConsoleAppender

# Specifies the format of the log output: Flexible format
log4j.appender.console.layout=org.apache.log4j.patternlayout
# Concrete format content%d: Date   %p: Time   %c: Priority   %M: Method  %m%n: Printed information  
log4j.appender.console.layout.conversionpattern=%d%p%c.%m ()-%m%n
 
 
############# log output to file #############
log4j.appender.file=org.apache.log4j.rollingfileappender
# File parameters: Specify the log file path
log4j.appender.file.file=. /logs/mylog.log
# File parameter: Specify maximum log file size
log4j.appender.file.maxfilesize=5kb
# file parameter: Specifies the maximum number
of log files generated log4j.appender.file.maxbackupindex=100
# log format
log4j.appender.file.layout= Org.apache.log4j.PatternLayout
log4j.appender.file.layout.conversionpattern=%d%c.%m ()-%m%n

code example

public class MyLog {
	 Logger log = Logger.getlogger (Test.class);
	@Test Public
	Void Demo () {
		try {
			log.info ("Logic code Start");
			int i = 1/0;
			Log.info ("Logical Code End");
		} catch (Exception e) {
			e.printstacktrace ();
			Log.error ("error message", E);}}}

Output display