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Getting a value from a checkbox

M Burke
Ranch Hand

Joined: Jun 25, 2004
Posts: 388
I can't seem to retrieve a value from a checkbox. It is either checked or unchecked, a boolean. So how do I extract its value when it reaches the servlet?

<INPUT type="checkbox" value="guessorall" checked>

then once the form is submitted and sent to the servlet I do this...

String guessall = req.getParameter("guessorall");

It always returns null.
Bear Bibeault
Author and ninkuma
Marshal

Joined: Jan 10, 2002
Posts: 60822
    
  65

You need to set the name attribute of the checkbox. The name will become the request parameter, and if checked, its value will be the value of the value attribute. if unchecked, no request parameter will be created for it.


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Bear Bibeault
Author and ninkuma
Marshal

Joined: Jan 10, 2002
Posts: 60822
    
  65

For example



This will result, if checked, in a request parameter named 'xyz' whose value is the string 'true' (easily converted to a boolean). If unchecked, no 'xyz' parameter will be present.
Kiran Sonaje
Greenhorn

Joined: Aug 23, 2004
Posts: 23
Hi,
This code may help u
All the best


import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
public class HttpRequestDemoServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<HTML>");
out.println("<HEAD>");
out.println("<TITLE>Obtaining Multi-Value Parameters</TITLE>");
out.println("</HEAD>");
out.println("<BODY>");
out.println("<BR>");
out.println("<BR>Select your favorite music:");
out.println("<BR><FORM METHOD=POST>");
out.println("<BR><INPUT TYPE=CHECKBOX " +
"NAME=favoriteMusic VALUE=Rock>Rock");
out.println("<BR><INPUT TYPE=CHECKBOX " +
"NAME=favoriteMusic VALUE=Jazz>Jazz");
out.println("<BR><INPUT TYPE=CHECKBOX " +
"NAME=favoriteMusic VALUE=Classical>Classical");
out.println("<BR><INPUT TYPE=CHECKBOX " +
"NAME=favoriteMusic VALUE=Country>Country");
out.println("<BR><INPUT TYPE=SUBMIT VALUE=Submit>");
out.println("</FORM>");
out.println("</BODY>");
out.println("</HTML>");
}
public void doPost(HttpServletRequest request, HttpServletResponse
response) throws ServletException, IOException {
String[] values = request.getParameterValues("favoriteMusic");
response.setContentType("text/html");
PrintWriter out = response.getWriter();
if (values != null ) {
int length = values.length;
out.println("You have selected: ");
for (int i=0; i<length; i++) {
out.println("<BR>" + values[i]);
}
}
}
}
M Burke
Ranch Hand

Joined: Jun 25, 2004
Posts: 388
yes, that helps. Thanks
 
It is sorta covered in the JavaRanch Style Guide.
 
subject: Getting a value from a checkbox
 
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