log4j使用--http://www.cnblogs.com/eflylab/archive/2007/01/11/618001.html

package log4jTest.com;

import java.io.FileReader;

import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;

public interface log4jDemo {
	public static void main(String[] args) {
		Logger logger = Logger.getLogger(log4jDemo.class);
        
        //使用默认的配置信息，不需要写log4j.properties
        BasicConfigurator.configure();
        //设置日志输出级别为info，这将覆盖配置文件中设置的级别
        logger.setLevel(Level.INFO);
        //下面的消息将被输出
        logger.info("this is an info");
        logger.warn("this is a warn");
        logger.error("this is an error");
        logger.fatal("this is a fatal");
	}
}

package log4jTest.com;

import java.io.FileReader;

import org.apache.log4j.BasicConfigurator;
import org.apache.log4j.FileAppender;
import org.apache.log4j.Level;
import org.apache.log4j.Logger;
import org.apache.log4j.SimpleLayout;

public interface log4jDemo {
	public static void main(String[] args) {
		Logger logger = Logger.getLogger(log4jDemo.class);
        
		SimpleLayout layout=new SimpleLayout();
		FileAppender appender=null;
		
		try
        {
            //把输出端配置到F:/logs/log.log
            appender = new FileAppender(layout,"F:/logs/log.log",false);
        }catch(Exception e){   
        	e.printStackTrace();
        }
		logger.addAppender(appender);//添加输出端
        logger.setLevel((Level)Level.DEBUG);//覆盖配置文件中的级别

        logger.info("this is an info");
        logger.warn("this is a warn");
        logger.error("this is an error");
        logger.fatal("this is a fatal");
	}
}

　　

　　

一直都报这个这就有点痛苦了,下面的配置文件加上红色的就ok了，具体原因不解