Log4jInit 类源代码
 1public class Log4jInit extends HttpServlet {
 2
 3         static Logger logger = Logger.getLogger(Log4jInit.class);
 4
 5         public Log4jInit() { 
 6         } 
 7
 8         public void init(ServletConfig config) throws ServletException { 
 9             String prefix = config.getServletContext().getRealPath("/"); 
10             String file = config.getInitParameter("log4j"); 
11             String filePath = prefix + file;
12             Properties props = new Properties();
13             try { 
14                 FileInputStream istream = new FileInputStream(filePath);
15                 props.load(istream); 
16                 istream.close(); 
17                 //toPrint(props.getProperty("log4j.appender.file.File"));
18                 String logFile = prefix + props.getProperty("log4j.appender.file.File");//设置路径
19                    props.setProperty("log4j.appender.file.File",logFile);
20                 PropertyConfigurator.configure(props);//装入log4j配置信息 
21             } catch (IOException e) { 
22                 toPrint("Could not read configuration file [" + filePath + "]."); 
23                 toPrint("Ignoring configuration file [" + filePath + "]."); 
24                 return; 
25             } 
26         } 
27
28         public static void toPrint(String content) { 
29             System.out.println(content); 
30         } 
31}

web.xml 中相关配置
1       <servlet> 
2         <servlet-name>log4j-init</servlet-name> 
3         <servlet-class>Log4jInit</servlet-class>
4         <init-param> 
5           <param-name>log4j</param-name> 
6           <param-value>WEB-INF/classes/log4j.properties</param-value> 
7         </init-param> 
8         <load-on-startup>1</load-on-startup> 
9       </servlet>

Code
package wbb.bysxxglxt.util;

import org.apache.struts.action.*; 
import org.apache.commons.logging.LogFactory; 
import org.apache.commons.logging.Log; 
import javax.servlet.ServletException; 
import java.util.Properties; 
import java.io.InputStream; 
import org.apache.log4j.PropertyConfigurator; 
import java.io.FileInputStream; 
import java.io.IOException;

public class ExtendedActionServlet extends ActionServlet {

private Log log = LogFactory.getLog(this.getClass().getName());

public ExtendedActionServlet() {}

public void init() throws ServletException {
             log.info("Initializing, My MyActionServlet init this System’s Const Variable"); 
             String prefix = this.getServletConfig().getServletContext().getRealPath("/");
             String file = this.getServletConfig().getInitParameter("log4j"); 
             String filePath = prefix + file; 
             Properties props = new Properties(); 
             System.out.println(prefix); 
             System.out.println(file); 
             System.out.println(filePath);

try { 
                 FileInputStream log4jStream = new FileInputStream(filePath); 
                 props.load(log4jStream);
                 log4jStream.close(); 
                 String logFile = prefix + 
                                 props.getProperty("log4j.appender.A1.File"); //设置路径]
                 System.out.println(logFile); 
                 props.setProperty("log4j.appender.A1.File", logFile);
                 PropertyConfigurator.configure(props); //装入log4j配置信息 
             } catch (IOException e) { 
                 e.printStackTrace(); 
            } 
             log.info("Initializing, end My Init");
             super.init(); //应用了struts,此方法不能省，ActionServlet覆盖了的此方法中有很多重要操作 
         } 
}

web.xml 中相关配置
 1       <servlet> 
 2         <servlet-name>action</servlet-name> 
 3         <servlet-class>wbb.bysxxglxt.util.ExtendedActionServlet</servlet-class> 
 4         <init-param> 
 5           <param-name>config</param-name> 
 6           <param-value>/WEB-INF/struts-config.xml</param-value> 
 7         </init-param> 
 8         <init-param> 
 9             <param-name>log4j</param-name> 
10             <param-value>properties\\log4j.properties</param-value>                     
11           </init-param> 
12         <init-param> 
13           <param-name>debug</param-name> 
14           <param-value>0</param-value> 
15         </init-param> [Page]
16         <init-param> 
17           <param-name>application</param-name> 
18           <param-value>ApplicationResources</param-value> 
19         </init-param> 
20         <load-on-startup>0</load-on-startup> 
21       </servlet> 
22       <servlet-mapping> 
23         <servlet-name>action</servlet-name> 
24         <url-pattern>*.do</url-pattern> 
25       </servlet-mapping>

Code
### 设置logger级别 ###
log4j.rootLogger=DEBUG,stdout,A1

### appender.stdout输出到控制台 ###
log4j.appender.stdout=org.apache.log4j.ConsoleAppender 
log4j.appender.stdout.Target=System.out 
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout 
log4j.appender.stdout.layout.ConversionPattern= [%5p] [BYSXXGLXT] %d{yyyy-MM-dd HH:mm:ss}: %-4r [%-5p] [%t] ( %F,%L ) - %m%n

### appender.A1输出到日志文件 ### 
log4j.appender.A1=org.apache.log4j.DailyRollingFileAppender [Page]
log4j.appender.A1.File=WEB-INF\\\\logs\\\\bysxxglxt.log 
##注意上面日志文件相对应用根目录路径的写法 
log4j.appender.A1.DatePattern=’.’yyyy-MM-dd’.log’ 
log4j.appender.A1.Append=true 
## 输出DEBUG级别以上的日志 
log4j.appender.A1.Threshold=DEBUG 
log4j.appender.A1.layout=org.apache.log4j.PatternLayout 
log4j.appender.A1.layout.ConversionPattern= [%5p] [BYSXXGLXT] %d{yyyy-MM-dd HH:mm:ss}: %-4r     [%t] ( %F,%L ) - %m%n