引入依赖

<dependency>
      <groupId>log4j</groupId>
       <artifactId>log4j</artifactId>
      <version>1.2.17</version>
 </dependency>
 <!--日志门面,服务所有日志框架-->
 <dependency>
      <groupId>org.slf4j</groupId>
      <artifactId>slf4j-api</artifactId>
      <version>1.7.25</version>
  </dependency>

引入配置文件 log4j.properties

log4j.rootLogger=CONSOLE,stdout,logfile

#stdout控制器
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.Target=System.out
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

#输出格式
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c]:%L - %m%n

#文件路径输出
log4j.appender.logfile=org.apache.log4j.RollingFileAppender
log4j.appender.logfile.File=D:/mylog.log
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n

开发程序

public class Demo1 {
   private static Logger logger = Logger.getLogger(Demo1.class);

    public static void main(String[] args) {
        //下面的消息将被输出到控制台
        logger.info("this is an info");
        logger.warn("this is a warn");
        logger.error("this is an error");
    }
}