Following is the generic example which uses getParameterNames() method of HttpServletRequest to read all the available form parameters. This method returns an Enumeration that contains the parameter names in an unspecified order

Once we have an Enumeration, we can loop down the Enumeration in standard way by, using hasMoreElements() method to determine when to stop and using nextElement() method to get each parameter name.

// Import required java libraries

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

import java.util.*;




// Extend HttpServlet class

public class ReadParams extends HttpServlet {




   // Method to handle GET method request.

   public void doGet(HttpServletRequest request, HttpServletResponse response)

      throws ServletException, IOException {

     

      // Set response content type

      response.setContentType("text/html");




      PrintWriter out = response.getWriter();

      String title = "Reading All Form Parameters";

      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" +

         "<table width = \"100%\" border = \"1\" align = \"center\">\n" +

         "<tr bgcolor = \"#949494\">\n" +

            "<th>Param Name</th>"

            "<th>Param Value(s)</th>\n"+

         "</tr>\n"

      );




      Enumeration paramNames = request.getParameterNames();




      while(paramNames.hasMoreElements()) {

         String paramName = (String)paramNames.nextElement();

         out.print("<tr><td>" + paramName + "</td>\n<td>");

         String[] paramValues = request.getParameterValues(paramName);




         // Read single valued data

         if (paramValues.length == 1) {

            String paramValue = paramValues[0];

            if (paramValue.length() == 0)

               out.println("<i>No Value</i>");

               else

               out.println(paramValue);

         } else {

            // Read multiple valued data

            out.println("<ul>");




            for(int i = 0; i < paramValues.length; i++) {

               out.println("<li>" + paramValues[i]);

            }

            out.println("</ul>");

         }

      }

      out.println("</tr>\n</table>\n</body></html>");

   }

  

   // Method to handle POST method request.

   public void doPost(HttpServletRequest request, HttpServletResponse response)

      throws ServletException, IOException {

     

      doGet(request, response);

   }

}

Now, try the above servlet with the following form −

<html>

   <body>

      <form action = "ReadParams" method = "POST" target = "_blank">

         <input type = "checkbox" name = "maths" checked = "checked" /> Maths

         <input type = "checkbox" name = "physics"  /> Physics

         <input type = "checkbox" name = "chemistry" checked = "checked" /> Chem

         <input type = "submit" value = "Select Subject" />

      </form>

   </body>

</html>

Now calling servlet using the above form would generate the following result −

Reading All Form Parameters

Param Name	Param Value(s)
maths	on
chemistry	on

You can try the above servlet to read any other form’s data having other objects like text box, radio button or drop down box etc.

So, this brings us to the end of blog. This Tecklearn ‘Reading checkbox Data’ 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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