Java Servlet makes this job easy by providing you a mechanism where you can make a webpage in such a way that it would refresh automatically after a given interval.
The simplest way of refreshing a web page is using method setIntHeader() of response object. Following is the signature of this method:
public void setIntHeader(String header, int headerValue)This method sends back header "Refresh" to the browser along with an integer value which indicates time interval in seconds.
Auto Page Refresh Example:
This example shows how a servlet performs auto page refresh using setIntHeader() method to set Refresh header.// 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 =
"<!doctype html public \"-//w3c//dtd html 4.0 " +
"transitional//en\">\n";
out.println(docType +
"<html>\n" +
"<head><title>" + title + "</title></head>\n"+
"<body bgcolor=\"#f0f0f0\">\n" +
"<h1 align=\"center\">" + title + "</h1>\n" +
"<p>Current Time is: " + CT + "</p>\n");
}
// Method to handle POST method request.
public void doPost(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
Now let us compile above servlet and create following entries in web.xml....
<servlet>
<servlet-name>Refresh</servlet-name>
<servlet-class>Refresh</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>Refresh</servlet-name>
<url-pattern>/Refresh</url-pattern>
</servlet-mapping>
....
Now call this servlet using URL http://localhost:8080/Refresh which
would display current system time after every 5 seconds as follows. Just
run the servlet and wait to see the result:| Auto Page Refresh using Servlet Current Time is: 9:44:50 PM |
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