In this blog, we will discuss page redirecting with JSP. Page redirection is generally used when a document moves to a new location and we need to send the client to this new location. This can be because of load balancing, or for simple randomization.

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

public void response.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 the setStatus() and the setHeader() methods together to achieve the same redirection example −

....

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

response.setStatus(response.SC_MOVED_TEMPORARILY);

response.setHeader("Location", site);

....

Example

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

<%@ page import = "java.io.*,java.util.*" %>




<html>

   <head>

      <title>Page Redirection</title>

   </head>

  

   <body>

      <center>

         <h1>Page Redirection</h1>

      </center>

      <%

         // New location to be redirected

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

         response.setStatus(response.SC_MOVED_TEMPORARILY);

         response.setHeader("Location", site);

      %>

   </body>

</html>

Let us now put the above code in PageRedirect.jsp and call this JSP using the URL http://localhost:8080/PageRedirect.jsp. This would take you to the given URL http://www.photofuntoos.com.

JSP – Hits Counter

A hit counter tells you about the number of visits on a particular page of your web site. Usually you attach a hit counter with your index.jsp page assuming people first land on your home page.

To implement a hit counter you can make use of the Application Implicit object and associated methods getAttribute() and setAttribute().

This object is a representation of the JSP page through its entire lifecycle. This object is created when the JSP page is initialized and will be removed when the JSP page is removed by the jspDestroy() method.

Following is the syntax to set a variable at application level −

application.setAttribute(String Key, Object Value);

You can use the above method to set a hit counter variable and to reset the same variable. Following is the method to read the variable set by the previous method −

application.getAttribute(String Key);

Every time a user accesses your page, you can read the current value of the hit counter and increase it by one and again set it for future use.

Example

This example shows how you can use JSP to count the total number of hits on a particular page. If you want to count the total number of hits of your website then you will have to include the same code in all the JSP pages.

<%@ page import = "java.io.*,java.util.*" %>




<html>

   <head>

      <title>Application object in JSP</title>

   </head>

  

   <body>

      <%

         Integer hitsCount = (Integer)application.getAttribute("hitCounter");

         if( hitsCount ==null || hitsCount == 0 ) {

            /* First visit */

            out.println("Welcome to my website!");

            hitsCount = 1;

         } else {

            /* return visit */

            out.println("Welcome back to my website!");

            hitsCount += 1;

         }

         application.setAttribute("hitCounter", hitsCount);

      %>

      <center>

         <p>Total number of visits: <%= hitsCount%></p>

      </center>

  

   </body>

</html>

Let us now put the above code in main.jsp and call this JSP using the URL http://localhost:8080/main.jsp. This will display the hit counter value which increases as and when you refresh the page. You can try accessing the page using different browsers and you will find that the hit counter will keep increasing with every hit and you will receive the result as follows −

Welcome back to my website!

Total number of visits: 12

Hit Counter Resets

What when you restart your application, i.e., web server, this will reset your application variable and your counter will reset to zero. To avoid this loss, consider the following points −

Define a database table with a single count, let us say hitcount. Assign a zero value to it.
With every hit, read the table to get the value of hitcount.
Increase the value of hitcount by one and update the table with new value.
Display new value of hitcount as total page hit counts.
If you want to count hits for all the pages, implement above logic for all the pages.

JSP – Auto 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 Webpage regularly using refresh or reload button with your browser.

JSP 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 Webpage is by using the setIntHeader() method of the response object. Following is the signature of this method −

public void setIntHeader(String header, int headerValue)

This method sends back the header “Refresh” to the browser along with an integer value which indicates time interval in seconds.

Auto Page Refresh Example

In the following example, we will use the setIntHeader() method to set Refresh header. This will help simulate a digital clock −

<%@ page import = "java.io.*,java.util.*" %>




<html>

   <head>

      <title>Auto Refresh Header Example</title>

   </head>

  

   <body>

      <center>

         <h2>Auto Refresh Header Example</h2>

         <%

            // Set refresh, autoload time as 5 seconds

            response.setIntHeader("Refresh", 5);

           

            // 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;

            out.println("Crrent Time: " + CT + "\n");

         %>

      </center>

  

   </body>

</html>

Now put the above code in main.jsp and try to access it. This will display the current system time after every 5 seconds as follows. Just run the JSP and wait to see the result −

Auto Refresh Header Example

Current Time is: 9:44:50 PM

So, this brings us to the end of blog. This Tecklearn ‘Page Redirecting and Hits Counter 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 JSP 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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