无非就是两种方法
1：Servlet
2: Listener
 
Servlet:
package  

 import  org.apache.log4j.Logger;
 import  javax.servlet.http.HttpServlet;
 import  java.util.Calendar;
 import  java.util.Date;
 import  java.util.Timer;
 import  java.util.TimerTask;

 /**
 *  @author  martin
  */
public   class  LuceneTimerServlet  extends  HttpServlet {
     private   static  Logger logger  =  Logger.getLogger(LuceneTimerServlet. class );
     private   static  Timer timer;

     static  {
        timer  =   new  Timer( true );
        timer.schedule( new  TimerTask() {
             public   void  run() {
                System.out.println( " 开始创建索引@ "   +  getTime(Calendar.getInstance()));
                TaxDocIndexer indexer  =   new  TaxDocIndexer();
                indexer.setFirstRun(Boolean.TRUE);
                indexer.fetch();
                System.out.println( " 索引创建成功@ "   +  getTime(Calendar.getInstance()));
            }
        },
                getFirstTime(),
                getPeriod()
        );
    }


     public   void  destroy() {
        logger.debug( " LuceneTimerServlet.destroy() begin " );
        timer.cancel();
    }

     /**
     * 从服务启动起算，第二天零时开始执行
     *
     *  @return  Timer第一次执行时间
      */
     private   static  Date getFirstTime() {
        Calendar calendar  =  Calendar.getInstance();
        calendar.add(Calendar.DAY_OF_YEAR,  1 );
        calendar.set(Calendar.HOUR_OF_DAY,  0 );
        calendar.set(Calendar.MINUTE,  0 );
        calendar.set(Calendar.SECOND,  0 );
        logger.debug( " 开始执行时间： "   +  getTime(calendar));
         return  calendar.getTime();
    }

     /**
     *  @param  calendar
     *  @return  formated time string
      */
     private   static  String getTime(Calendar calendar) {
         return   new  StringBuffer()
                .append(calendar.get(Calendar.YEAR)).append( " 年 " )
                .append(calendar.get(Calendar.MONTH)  +   1 ).append( " 月 " )
                .append(calendar.get(Calendar.DAY_OF_MONTH)).append( " 日   " )
                .append(calendar.get(Calendar.HOUR_OF_DAY)).append( " 时 " )
                .append(calendar.get(Calendar.MINUTE)).append( " 分 " )
                .append(calendar.get(Calendar.SECOND)).append( " 秒 " )
                .toString();
    }

     /**
     * 计算一天的时间间隔
     * 一天24小时×每小时60分×每分60秒×1000
     *
     *  @return  一天时间
      */
     private   static   long  getPeriod() {
         return   86400000 ;
    }
}
配置web.xml
     < servlet >
         < servlet-name > luceneTimerServlet servlet-name >
         < servlet-class > sompackage.servlet.LuceneTimerServlet servlet-class >
         < load-on-startup > 1 load-on-startup >
     servlet >


如果采用Listener,则是：
     < listener >     
        < listener-class > sompackage.servlet.LuceneTimerServlet listener-class >
     listener >