📅 最后修改于: 2020-11-12 05:44:40 🧑 作者: Mango
考虑一个显示实时游戏得分或股票市场状态或货币汇率的网页。对于所有此类页面，您将需要使用浏览器的“刷新”或“重新加载”按钮定期刷新网页。
Java Servlet通过为您提供一种机制来简化此工作，使您可以以某种方式制作网页，使其在给定间隔后自动刷新。
刷新网页的最简单方法是使用响应对象的setIntHeader()方法。以下是此方法的签名-
public void setIntHeader(String header, int headerValue)
此方法将标头“ Refresh”连同指示时间间隔(以秒为单位)的整数一起发送回浏览器。
此示例显示servlet如何使用setIntHeader()方法设置Refresh标头来执行自动页面刷新。
// Import required java libraries
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.util.*;
// Extend HttpServlet class
public class Refresh extends HttpServlet {
// Method to handle GET method request.
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// Set refresh, autoload time as 5 seconds
response.setIntHeader("Refresh", 5);
// Set response content type
response.setContentType("text/html");
// Get current time
Calendar calendar = new GregorianCalendar();
String am_pm;
int hour = calendar.get(Calendar.HOUR);
int minute = calendar.get(Calendar.MINUTE);
int second = calendar.get(Calendar.SECOND);
if(calendar.get(Calendar.AM_PM) == 0)
am_pm = "AM";
else
am_pm = "PM";
String CT = hour+":"+ minute +":"+ second +" "+ am_pm;
PrintWriter out = response.getWriter();
String title = "Auto Page Refresh using Servlet";
String docType =
""-//w3c//dtd html 4.0 " + "transitional//en\">\n";
out.println(docType +
"\n" +
"" + title + " \n"+
"\n" +
"" + title + "
\n" +
"Current Time is: " + CT + "
\n"
);
}
// Method to handle POST method request.
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
现在让我们编译上面的servlet并在web.xml中创建以下条目
....
Refresh
Refresh
Refresh
/Refresh
....
现在，使用URL http：// localhost：8080 / Refresh调用此servlet，它每5秒显示一次当前系统时间，如下所示。只需运行servlet并等待查看结果-
Auto Page Refresh using Servlet
Current Time is: 9:44:50 PM