static Logger log= Logger.getLogger("qqtt");    public void log(){       log.debug("Debug info.");       log.info("Info info");       log.warn("Warn info");       log.error("Error info");       log.fatal("Fatal info");    }    public static void main(String[] args) {        // TODO Auto-generated method stub        Log4jTest l=new Log4jTest();        l.log();    }

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE log4j:configuration SYSTEM "log4j.dtd"><log4j:configuration xmlns:log4j=‘http://jakarta.apache.org/log4j/‘>  <appender name="_rolling" class="org.apache.log4j.RollingFileAppender">    <param name="Threshold" value="ERROR" />    <param name="File" value="log4j_test.log" />    <param name="Append" value="true" />    <param name="MaxFileSize" value="3MB" />    <!--default is 10KB, format=xxKB,xxMB,xxGB-->    <param name="MaxBackupIndex" value="3" />    <layout class="org.apache.log4j.PatternLayout">      <param name="ConversionPattern" value="[%d{yyyy-MM-dd HH:mm}] %-5p [%c]%n  %m%n" />    </layout>  </appender>  <appender name="console" class="org.apache.log4j.ConsoleAppender">    <layout class="org.apache.log4j.PatternLayout">      <param name="ConversionPattern" value="%d %-5p [%t] %C (%F:%L) - %m%n" />    </layout>  </appender>  <root>    <priority value="info" />      <appender-ref ref="_rolling" />    <appender-ref ref="console" />  </root></log4j:configuration>