Configuration and use of log4j

Benefits of using logs:

Log information can be saved for a long time.

Logs can be saved to: network, file, database

Sets the level of the log.

OFF

Fatal–system.exit (0); -JVM,

error– error, module error.

warn– Warning

Info-Programmer Debug Information-equivalent to System.err. And that's how we often output it.

Debug-system.out. – In general, the frame is used out.

On

Set Print level Up compatibility

LOG4J requires two files:

1, Guide Package Log4j.jar

2, log4j configuration file, this profile, must be located in Classpath, must be called: Log4j.properties

　　　　Log4j.properties Log Four components:

logger– Log class, set the log class. Design the root log.

appener– Append object. Log output target.

layout– the format of the log

Level levels

1 log4j.properties2 3 4 #设置logger的根日志, level, A1 refers to the target of the output5 Log4j.rootlogger=on,console,file6 #设置日志的appender-The target of the output7 #其他的还是RollingFileAppender8 Log4j.appender.console=org.apache.log4j.consoleappender9 #日志的格式, the format of the description log is specified by the program itselfTen Log4j.appender.console.layout=org.apache.log4j.patternlayout One #%d=date,%p=preority level, ALog4j.appender.console.layout.conversionpattern=%d{yyyy-mm-dd HH:mm:ss:SSS}%-5p%-10t%c<%l>%m%n -  -  the Log4j.appender.file=org.apache.log4j.rollingfileappender - #设置文件名 - Log4j.appender.file.file=d:/a/a.log - #设置文件最大大小 + log4j.appender.file.maxfilesize=10kb - #设置文件最多备份几个 + log4j.appender.file.maxbackupindex=3 A #日志的格式, the format of the description log is specified by the program itself at Log4j.appender.file.layout=org.apache.log4j.patternlayout -Log4j.appender.file.layout.conversionpattern=%d{yyyy-mm-dd HH:mm:ss:SSS}%-5p%-10t%c<%l>%m%n

Using Log4jdemo

1  PackageCn.test.demo;2 3 ImportOrg.apache.log4j.Logger;4 5  Public classLogdemo {6     StaticLogger Logg=logger.getlogger (Logdemo.class);7      Public Static voidMain (string[] args) {8Logg.fatal ("Fatal ...");9Logg.error ("Error ...");TenLogg.warn ("Warn ..."); OneLogg.info ("Info"); ALogg.debug ("Debug"); -System.err.println ("Over"); -     } the}

Configuration and use of log4j