Page redirection is a technique where the client is sent to a new location other than requested. Page redirection is generally used when a document moves to a new location or may be because of load balancing.

The simplest way of redirecting a request to another page is using method sendRedirect() of response object. Following is the signature of this method −

public void HttpServletResponse.sendRedirect(String location)

throws IOException

This method sends back the response to the browser along with the status code and new page location. You can also use setStatus() and setHeader() methods together to achieve the same −

....

String site = "http://www.newpage.com" ;

response.setStatus(response.SC_MOVED_TEMPORARILY);

response.setHeader("Location", site); 

....

Example

This example shows how a servlet performs page redirection to another location −

import java.io.*;

import java.sql.Date;

import java.util.*;

import javax.servlet.*;

import javax.servlet.http.*;




public class PageRedirect extends HttpServlet {

   

   public void doGet(HttpServletRequest request, HttpServletResponse response)

      throws ServletException, IOException {




      // Set response content type

      response.setContentType("text/html");




      // New location to be redirected

      String site = new String("http://www.photofuntoos.com");




      response.setStatus(response.SC_MOVED_TEMPORARILY);

      response.setHeader("Location", site);   

   }

}

Now let us compile above servlet and create following entries in web.xml

....

<servlet>

   <servlet-name>PageRedirect</servlet-name>

   <servlet-class>PageRedirect</servlet-class>

</servlet>




<servlet-mapping>

   <servlet-name>PageRedirect</servlet-name>

   <url-pattern>/PageRedirect</url-pattern>

</servlet-mapping>

....

Now call this servlet using URL http://localhost:8080/PageRedirect. This would redirect you to URL http://www.photofuntoos.com.

Servlets – Auto Page Refresh

Consider a webpage which is displaying live game score or stock market status or currency exchange ration. For all such type of pages, you would need to refresh your web page regularly using refresh or reload button with your browser.

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 the above servlet and create the 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

So, this brings us to the end of blog. This Tecklearn ‘Servlets – Page Redirection and Auto Refresh’ blog helps you with commonly asked questions if you are looking out for a job in Java Programming. If you wish to learn Servlets and build a career Java Programming domain, then check out our interactive, Java and JEE Training, that comes with 24*7 support to guide you throughout your learning period. Please find the link for course details:

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