在eclipse中新建一个项目，在src下新建一个log4j.properties文件，文件内容为下：
log4j.rootLogger = debug,stdout,D,E
log4j.appender.E = org.apache.log4j.DailyRollingFileAppender
log4j.appender.E.File =E://logs/error.log
log4j.appender.E.Append = true
log4j.appender.E.Threshold = ERROR
log4j.appender.E.layout = org.apache.log4j.PatternLayout

public class Test(){

    private static Logger logger = Logger.getLogger(Test.class);

    public static void main(String[] args){

        logger.error("this is error");

    }

}