log4j(二)

package com.ad.web.servlet;

import java.io.FileInputStream;
import java.io.IOException;
import java.util.Properties;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;

import org.apache.log4j.Logger;
import org.apache.log4j.PropertyConfigurator;


@SuppressWarnings("serial")
public class Log4jInit extends HttpServlet{
    
    static Logger log = Logger.getLogger(Log4jInit.class);

    public Log4jInit() {
    }

    public void init(ServletConfig config) throws ServletException {
        String prefix = config.getServletContext().getRealPath("/");
        String file = config.getInitParameter("log4j");
        String filePath = prefix + file;
        Properties props = new Properties();
        FileInputStream istream=null;
        try {
            istream = new FileInputStream(filePath);
            props.load(istream);
            istream.close();
           // String logFile = prefix + props.getProperty("log4j.appender.logfile.File");//设置路径
            String logFile =props.getProperty("log4j.appender.logfile.File");//设置路径
            
            props.setProperty("log4j.appender.logfile.File",logFile);
            PropertyConfigurator.configure(props);//装入log4j配置信息
            log.error("************************load log4j");
        }
        catch (IOException e)
        {
           log.error("Log4jInit init is error",e);
            return;
        }
        finally
        {
            if(istream!=null)
            {
                try
                {
                    istream.close();
                }
                catch (IOException e)
                {
                    log.error("Log4jInit init is error",e);
                }
            }
        }
    }

}

    <!-- 初如化日志 -->
    <servlet>
        <servlet-name>log4j-init</servlet-name>
        <servlet-class>com.ad.web.servlet.Log4jInit</servlet-class>
        <init-param>
            <param-name>log4j</param-name>
            <param-value>WEB-INF/classes/log4j.properties</param-value>
        </init-param>
        <load-on-startup>0</load-on-startup>
    </servlet>