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Imagine, if you want to live broadcast the score of a match, or the real-time status of the stock market, or the current foreign exchange allocation, how can you achieve this? Clearly, to implement this real-time function, you have to refresh the page regularly.
JSP provides a mechanism to make this task easier, allowing the page to refresh automatically at regular intervals.
The simplest way to refresh a page is to use the setIntHeader() method of the response object. The signature of this method is as follows:
public void setIntHeader(String header, int headerValue)
This method notifies the browser to refresh after a given time, with the time in seconds.
This example uses the setIntHeader() method to set the refresh header and simulate a digital clock:
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@ page import="java.io.*,java.util.*" %>
<html>
<head>
<title>Auto Refresh Example</title>
</head>
<body>
<h2>Auto Refresh</h2>
<%
// Set every5seconds refresh
response.setIntHeader("Refresh", 5);
// Get the 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;
out.println("Current time is: " + CT + "\n");
%>
</body>
</html>
Save the above code in the main.jsp file and access it. It will refresh every5seconds refresh the page and get the current system time. The running result is as follows:
Auto Refresh Current time is: 6:5:36 PM
You can also write a more complex program yourself.