在程序中加入Log4j调试代码的方法！

用法：

启动Servlet:

/*
* Created on 2005-3-2
*
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
*/
package com.beltino.util;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import org.apache.log4j.PropertyConfigurator;
/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
public class Log4jInit extends HttpServlet {

/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occure
*/
public void init() throws ServletException {
    String prefix = getServletContext().getRealPath("/");
    String file = getInitParameter("log4j");
    if (file != null) {
      PropertyConfigurator.configure(prefix + file);
    }
}

}

2、web.xml中:
  <servlet>
    <servlet-name>Log4jInit</servlet-name>
    <display-name>This is the display name of my J2EE component</display-name>
    <description>This is the description of my J2EE component</description>
    <servlet-class>com.beltino.util.Log4jInit</servlet-class>
<init-param>
      <param-name>log4j</param-name>
      <param-value>/WEB-INF/classes/log4j.properties</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>

程序中加入
static Logger helloAppLogger=Logger.getLogger(类名.class);

需要的地方:
   helloAppLogger.error("error")
   helloAppLogger.info("info");
   ...

配置文件:log4j.properties放到web-info\classes下

#定义log
log4j.rootLogger=info,console,file,DATABASE
#log4j.rootLogger=info,file,DATABASE
#log4j.rootLogger=error,file,DATABASE
#定义控制台
log4j.appender.console=org.apache.log4j.ConsoleAppender
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern=%r [%t] %-5p %c (%F:%L) %x - %m%n
#定义数据库
log4j.appender.DATABASE=org.apache.log4j.jdbc.JDBCAppender
log4j.appender.DATABASE.URL=jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=communitymedical
log4j.appender.DATABASE.driver=com.microsoft.jdbc.sqlserver.SQLServerDriver
log4j.appender.DATABASE.user=sa
log4j.appender.DATABASE.password=btn
log4j.appender.DATABASE.sql=INSERT INTO TLOG4J VALUES ('%-5p','%d{yyyy-mm-dd hh:mm:ss}  %-5p (%F:%L) - %m%n','%d{yyyy-mm-dd hh:mm:ss}')
log4j.appender.DATABASE.layout=org.apache.log4j.PatternLayout
log4j.appender.DATABASE.layout.ConversionPattern=%d  %-5p (%F:%L) - %m%n
#定义文件
log4j.appender.file=org.apache.log4j.DailyRollingFileAppender
log4j.appender.file.File=G:/Tomcat5/webapps/communitymedical/log/test
#log4j.appender.file.MaxFileSize=10KB
#log4j.appender.file.MaxBackupIndex=1
log4j.appender.file.DatePattern='.'yyyy-MM-dd'.log'
log4j.appender.file.layout=org.apache.log4j.PatternLayout
log4j.appender.file.layout.ConversionPattern=%d  %-5p (%F:%L) - %m%n