java中timer在web.xml中的一个例子

分三步

一、定时执行的任务类Daemon

二、扩展HttpServlet的servlet

三、配置web.xml文件

细节如下：

一、定时执行的任务类Daemon


package com.resoft.recis.common.timer;




import java.sql.Connection;


import java.sql.DriverManager;


import java.sql.ResultSet;


import java.sql.SQLException;


import java.sql.Statement;


import java.text.SimpleDateFormat;


import java.util.Calendar;


import java.util.Date;


import java.util.Timer;


import java.util.TimerTask;




import javax.servlet.ServletException;






/** *//**


* Function:


* User : zxs_9999


* Date :


*/




public class Daemon ...{


private static final Timer timer = new Timer();






// private static String sDBDriver = "com.ibm.db2.jcc.DB2Driver";


// private static String url="jdbc:db2://127.0.0.1:50000/test";


// private static String user="db2";


// private static String password="db2";


private static String sDBDriver = "com.microsoft.jdbc.sqlserver.SQLServerDriver";


private static String url="jdbc:microsoft:sqlserver://127.0.0.1:1433;DatabaseName=test";


private static String user="sql";


private static String password="sql";






private static Connection conn = null;


private static ResultSet rs = null;








static...{




try ...{


Class.forName(sDBDriver);






}catch(java.lang.ClassNotFoundException e)...{


System.out.println("in Jdbc() , ClassNotFoundException");


e.printStackTrace();




}catch(Exception e)...{


System.out.println("in Jdbc() , after ClassNotFoundException's Exception");


e.printStackTrace();


}


}




public static void start()...{






timer.scheduleAtFixedRate(new TimerTask()...{






public void run()...{


Calendar calendar = Calendar.getInstance();


int hour = calendar.get(Calendar.HOUR_OF_DAY);


System.out.println("run hour: "+hour);


//20点以后再执行




if(hour>=20 && hour<=22)...{




ResultSet RS = executeQuery("SELECT * FROM OrgMng");


Date workdate=null;




try ...{


rs.next();


workdate=rs.getDate("workdate");


RS.close();


executeUpdate("update OrgMng set workdate ='"+changeDate(workdate)+"'");




} catch (Exception e) ...{


// TODO: handle exception


System.out.println("in start() , Exception");


e.printStackTrace();


}


}


}




}


,0,1000*60*60*2);//两个小时1000*60*60*2 自动执行一次


System.out.println("timer 自动更新日期程序启动...");


}






public static ResultSet executeQuery(String sql) ...{


rs = null;




try ...{


conn= DriverManager.getConnection(url,user,password);


Statement stmt = conn.createStatement();


rs = stmt.executeQuery(sql);




}catch(SQLException ex) ...{


System.out.println("in executeQuery , SQLException");


ex.printStackTrace();




}catch(Exception e)...{


System.out.println("in executeQuery , after SQLException's Exception");


e.printStackTrace();


}


return rs;


}






public static void executeUpdate(String sql) ...{




try ...{


//conn = DriverManager.getConnection(url);


conn= DriverManager.getConnection(url,user,password);


Statement stmt = conn.createStatement();


stmt.executeUpdate(sql);




}catch(SQLException ex) ...{


System.out.println("in executeUpdate , SQLException");


ex.printStackTrace();




}catch(Exception e)...{


System.out.println("in executeUpdate , after SQLException's Exception");


e.printStackTrace();


}


}






public static String changeDate(Date workdate)...{


String temp=null;




try...{


SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");


Calendar calendar=Calendar.getInstance();


calendar.setTime(workdate);


calendar.add(Calendar.DATE, 1);


temp=sdf.format(calendar.getTime());


System.out.println("workdate is "+temp);




}catch(Exception e)...{


System.out.println("in changeDate ,Exception");


e.printStackTrace();


}


return temp;


}






public static void main(String[] args) throws ServletException ...{


Daemon.start();




}


}





二、扩展HttpServlet的servlet


package com.resoft.recis.common.timer;




import javax.servlet.http.HttpServlet;


import javax.servlet.ServletException;






/** *//**


* User: zxs_9999


* Date:


* Time:


*/




public class HttpImportDaemon extends HttpServlet...{




public void init() throws ServletException ...{


Daemon.start();


}




}





三、配置web.xml文件


<servlet>


<servlet-name>workdate</servlet-name>


<display-name>chage workdate</display-name>


<servlet-class>


com.resoft.recis.common.timer.HttpImportDaemon


</servlet-class>


<load-on-startup />


</servlet>




<servlet-mapping>


<servlet-name>workdate</servlet-name>


<url-pattern>/*</url-pattern>


</servlet-mapping>