[Java学习] 之Log4j学习

1.首先：下载log4j 

2.在WEB-INF中建立log4j.properties

   并可参考这段代码

log4j.rootLogger=DEBUG,A1,A2,A3,A4

###  system.out  ###
log4j.appender.A2 =org.apache.log4j.ConsoleAppender
log4j.appender.A2.Threshold=DEBUG
log4j.appender.A2.Target=System.out
###log4j.appender.A2.encoding=UTF-8
log4j.appender.A2.layout=org.apache.log4j.PatternLayout
log4j.appender.A2.layout.ConversionPattern=[%x] [%-d{yyyy-MM-dd HH:mm:ss}] [%p] %m%n

### file debug ###
log4j.appender.A1 = org.apache.log4j.DailyRollingFileAppender
log4j.appender.A1.File = ../logs/run/DServerDebug.log
log4j.appender.A1.DatePattern='.'yyyy-MM-dd
###log4j.appender.A1.MaxFileSize=100MB
log4j.appender.A1.encoding=UTF-8
log4j.appender.A1.Append = true
log4j.appender.A1.Threshold = DEBUG
log4j.appender.A1.layout = org.apache.log4j.PatternLayout
log4j.appender.A1.layout.ConversionPattern=[%x] [%-d{yyyy-MM-dd HH:mm:ss}] [%p] %m%n
 
### file INFO ###
log4j.appender.A3 = org.apache.log4j.DailyRollingFileAppender
log4j.appender.A3.File = ../logs/run/DServerINFO.log
log4j.appender.A3.DatePattern='.'yyyy-MM-dd
###log4j.appender.A3.MaxFileSize=10MB
log4j.appender.A3.encoding=UTF-8
log4j.appender.A3.Append = true
log4j.appender.A3.Threshold = INFO
log4j.appender.A3.layout = org.apache.log4j.PatternLayout
log4j.appender.A3.layout.ConversionPattern=[%x] [%-d{yyyy-MM-dd HH:mm:ss}] [%p] %m%n

 
### file ERROR ###
log4j.appender.A4 = org.apache.log4j.DailyRollingFileAppender
log4j.appender.A4.File = ../logs/run/DServerERROR.log
log4j.appender.A4.DatePattern='.'yyyy-MM-dd
###log4j.appender.A4.MaxFileSize=100MB
log4j.appender.A4.encoding=UTF-8
log4j.appender.A4.Append = true
log4j.appender.A4.Threshold = ERROR
log4j.appender.A4.layout = org.apache.log4j.PatternLayout
log4j.appender.A4.layout.ConversionPattern=[%x] [%-d{yyyy-MM-dd HH:mm:ss}] [%p] %m%n

可根据不同的项目 修改不同的参数就可以了。 具体参数的作用可参考此文章：http://blog.sina.com.cn/s/blog_7096a4800100pa5c.html

3.在这里 由于我用的是Servlet 所以在 Web.xml中加入了 Servlet的配置

<!-- 开始 Log4j Servlet配置 -->  
    <servlet>  
        <servlet-name>log4j-init</servlet-name>  
        <servlet-class>application.Log4jInit</servlet-class><!--log4j初始化servlet类的包路径-->  
        <init-param>  
        <param-name>log4j</param-name>  
        <param-value>WEB-INF/log4j.properties</param-value><!--log4j配置文件路径-->
      <!--log4j配置文件路径或者写成绝对路径，比如：C:Program Filesapache-tomcat-6.0.35wordlog4j.properties-->
        </init-param>  
        <load-on-startup>1</load-on-startup>  
    </servlet>  
<!--结束 Log4j Servlet配置-->

 4.编写初始化类：log4jInit

package application;
 
import javax.servlet.http.HttpServlet;
import org.apache.log4j.PropertyConfigurator;
 
/*
 *  初始化Log4J
 * 
 */
 
public class Log4jInit extends HttpServlet {
    public void init(ServletConfig config) throws ServletException()
    {
        String prefix = config.getServletContext().getRealPath("/");
        String file = config.getInitParameter("log4j");    
        System.out.println("日志的配置文件路径为："+prefix+file);
        if(file != null)
        {
            PropertyConfigurator.configure(prefix+file);  //载入配置文件
            System.out.println("日志的配置文件读取成功");
             
        }
    }
}

到这里准备工作就结束了 可以使用log4j来进行日志的记录了。

5.使用 

   在要用的地方

static Logger logger = Logger.getLogger(当前类.class);
logger.debug(content);