Java定时器在Web中的应用
＝＝＝＝＝＝＝＝＝＝Java定时器在Web中的应用＝＝＝＝＝＝＝＝＝＝
在web中,定时器的启动一般随web server的启动而启动,一般有两种方法.
方法一：在web.xml里配置一个Servlet，并设置其随web server的启动而启动。然后在该Servlet的init()方法里启动定时器，在destory()方法里销毁定时器。
方法二：在web.xml里配置一个Listener,然后在该Listener的初始化方法里启动定时器，在其销毁的方法朝左销毁定时器。
在servlet中启动定时器
java 代码
import java.io.IOException;??
import java.util.Timer;??
import javax.servlet.RequestDispatcher;??
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.commons.lang.StringUtils;??
public class ConvergeDataServlet extends HttpServlet {??
??? private static final long serialVersionUID = 1L;??
??? private Timer timer1 = null;??
??????
??? private Task task1;??
??????
??? /**
???? * Constructor of the object.
???? */
??? public ConvergeDataServlet() {??
??????? super();??
??? }??
??? /**
???? * Destruction of the servlet.
???? */
??? public void destroy() {??
??????? super.destroy();???
??????? if(timer1!=null){??
??????????? timer1.cancel();??
??????? }??
??? }??
??????
??? public void doGet(HttpServletRequest request, HttpServletResponse response)??
??????????? throws ServletException, IOException {??
??????????
??? }??
??????
??? public void doPost(HttpServletRequest request, HttpServletResponse response)??
??????????? throws ServletException, IOException {??
??????? doGet(request, response);?????????
??? }??
??? // init方法启动定时器??
??? public void init() throws ServletException {??
??????????
??????? ServletContext context = getServletContext();??
??????????
??????? // (true为用定时间刷新缓存)??
??????? String startTask = getInitParameter("startTask");??
??????????????????
??????? // 定时刷新时间(分钟)??
??????? Long delay = Long.parseLong(getInitParameter("delay"));??
??????????
??????? // 启动定时器??
??????? if(startTask.equals("true")){??
??????????? timer1 = new Timer(true);??
??????????? task1 = new Task(context);??
??????????? timer1.schedule(task1, delay * 60 * 1000, delay * 60 * 1000);??
??????? }??
??? }??
}??
定时执行操作
java 代码
/**
*??
* @author callan
*/
import java.util.TimerTask;??
import javax.servlet.ServletContext;??
public class Task extends TimerTask{??
??? private ServletContext context;??
??????
??? private static boolean isRunning = true;??
??????
??? public Task(ServletContext context){??
??????? this.context = context;??
??? }??
??????
??????????
??? @Override
??? public void run() {??
??????? if(isRunning){??
????????????
??????? }??
??? }??
}??
在web.xml配置这个servlet为服务启动时就调用servlet
<servlet></servlet>
< servlet >
???? < servlet-name >taskservlet< / servlet-name >
??? < servlet-class >com.task< /servlet-class >
??? < init-param >
???? < param-name >startTask< /param-name >
???? < param-value >true< /param-value >
??? < /init-param >
??? < init-param >
???? < param-name >intervalTime< /param-name >
???? < param-value >1< /param-value >
??? < /init-param >
??? < load-on-startup >300< /load-on-startup >
< /servlet >
<servlet></servlet>
?
