log4j使用方法

1、工程中引入log4j-1.2.14.jar

2、工程中增加一個servlet，來源程式如下：

package com.xgsj.servlets;
import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.PropertyConfigurator;

/**
類介紹：初始化log4j
開發人員：xjxhd
建立日期：

修改日期：
*/
public class InitLog4j extends HttpServlet {
    private static final String CONTENT_TYPE = "text/html; charset=GBK";
    public  static String CONTEXT_PATH="";
 /**
  * Constructor of the object.
  */
 public InitLog4j() {
  super();
 }

 /**
  * Destruction of the servlet. <br>
  */
 public void destroy() {
  super.destroy(); // Just puts "destroy" string in log
  // Put your code here
 }

 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

 }

 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

 }

 public void init() throws ServletException {
  // Put your code here
        ServletContext sct=getServletContext();
        String prefix = sct.getRealPath("/");
        CONTEXT_PATH=prefix;
        //log4j 設定檔存放目錄
        System.out.println("[....Log4j]: The Root Path: " + prefix);
        System.out.println("[....Log4j]: InitServlet init start...");
        String file = getInitParameter("log4j");
        //log4j 設定檔
        if (file != null) {
            PropertyConfigurator.configure(prefix + "/"+file);
            System.out.println("[....Log4j]:Property File's full name is :"+prefix + file);
            //根據配置初始化log4j
        }
        System.out.println("[....Log4j]: InitServlet Init Sucess...");
  
 }

}
注意紅色字型部分

3、在web.xml檔案中增加對上述servlet的引用

  <servlet>
    <servlet-name>InitLog4j</servlet-name>
    <servlet-class>com.xgsj.servlets.InitLog4j</servlet-class>
    <init-param>
      <param-name>log4j</param-name>
      <param-value>/WEB-INF/log4j.properties</param-value>
    </init-param>   
    <load-on-startup>1</load-on-startup>
  </servlet>

  <servlet-mapping>
    <servlet-name>InitLog4j</servlet-name>
    <url-pattern>/servlet/InitLog4j</url-pattern>
  </servlet-mapping>
4、在項目中增加log4j.properties檔案，例如上面紅色字型所示，該檔案放在WEB-INF下，檔案內容如下：

log4j.rootLogger=debug, stdout, R
#log4j.rootLogger=error, stdout, R

log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout

# Pattern to output the caller's file name and line number.
#log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n
log4j.appender.stdout.layout.ConversionPattern=%5p [%d{yyyy-MM-dd HH:mm:ss}] (%F:%L) - %m%n

#R
log4j.appender.R=org.apache.log4j.RollingFileAppender
#log4j.appender.R.File=/usr/IBM/WebSphere/AppServer/profiles/AppSrv01/installedApps/loopbackNode01Cell/PoliceWeb_war.ear/PoliceWeb.war/WEB-INF/logs/police.log
#log4j.appender.R.File==${webapp}//logs//police.log
#log4j.appender.R.File==../logs/police.log
log4j.appender.R.File=D://work//myeclipse//GsjOa//WebRoot//WEB-INF//logs//oa.log

log4j.appender.R.MaxFileSize=1024KB
# Keep one backup file
log4j.appender.R.MaxBackupIndex=10

log4j.appender.R.layout=org.apache.log4j.PatternLayout
log4j.appender.R.layout.ConversionPattern=%5p [%d{yyyy-MM-dd HH:mm:ss}] (%F:%L) - %m%n
注意上述路徑用兩個斜杠代表地址分割符

5、測試類別如下：

import com.xgsj.util.ConnDataBase;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.HashMap;
import org.apache.log4j.Logger;
import java.sql.Connection;
import java.util.*;

public class FunctionManager {
 
 public ArrayList queryAllModules()//查詢所有模組
 {
    Connection conn = null;
    Statement stmt = null;
    ResultSet rst=null;
    ArrayList ret=new ArrayList();

    String sql="select  * from modules order by mkbh";
    Logger logger=Logger.getRootLogger();
     logger.debug(sql);
     ConnDataBase db=new ConnDataBase();
     conn=db.getConnection();
     try
     {
            stmt = conn.createStatement();
            rst = stmt.executeQuery(sql);

           while (rst.next()) {
              HashMap hm=new HashMap();
              hm.put("mkbh",rst.getString("mkbh"));
              hm.put("mkmc",rst.getString("mkmc"));
              hm.put("mkxh", rst.getString("mkxh"));
              ret.add(hm);
           }
     }
     catch(Exception e)
     {
           e.printStackTrace();
     }
     finally{
           try
           {
             if (rst != null)
                   rst.close();
             if (stmt!=null)
                   stmt.close();
             if (conn!=null)
                   conn.close();
           }
           catch(Exception e)
           {
             e.printStackTrace();
           }
     }
     return ret; 
 }
｝

注意該類中的紅色字型，就是應用log4j的方法，好了，就那麼簡單，在log4j.properties中還可以指定輸出日誌的格式和輸出檔案的位置，自己試試。