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Need changes in JSP factorial program regarding to updation

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Posts: 56

posted 10 years ago

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Hi,
I have made a simple JSP code to find factorial of number which is as below,
Now I want some changes in this.

When I type number is textbox and submit data, I get result but the data from textbox is removed,
what if I want to keep the entered data as previously !!

Also clear button is also not working how to code in jsp to clear the form ??

Please guide me as I am beginner.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">

<html>
    <head>
        <title>Factorial of Number</title>
        
 		<script type="text/javascript">
		function num(e)	{
			var k;
			document.all ? k = e.keyCode : k = e.which;
			return (!((k > 64 && k < 91) || (k > 96 && k < 123) || k == 8));
		}
		</script>
    </head>

<body>
        <form name = "form" action = "factorial.jsp" method = "post">
            <table>
                <p>Enter numbers :- </p> 
        
                <tr><input type="text" name="num1" onkeypress="return num(event)"></tr>
                
                <tr align="center">
                	<td></td>
	                <td><input type = "submit" value = "Factorial" ></td>
	            </tr>
	            
	        </table>
	        <br>
            
		</form>
            
		<%!
            long factorial(long n)	{
            	if (n == 1) {
            		return n;
            	}
            	else {
            		return n * factorial(n - 1);
            	}
            }
		%>

<%
			if (request.getParameter("num1") != null)	{
		%>
		
		<table bgcolor="#F6E3CE" border="1" width="23%">
		
			<tr align="center">
			
			<%	long nm1 = Integer.parseInt(request.getParameter("num1"));	%>
				<td> Factorial of <%= request.getParameter("num1")%> is :-</td>
				<td> <%=factorial(nm1)%></td>
			</tr>
		</table>

<%	}	%>

</body> 
</html>

Ulf Dittmer

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Posts: 43081

posted 10 years ago

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If you want to populate the field with the previous value, your code will have to put it there. That's what the value attribute is for. Only if the value is not null, of course.

Also clear button is also not working how to code in jsp to clear the form ?

What is the use case for having one in your form? Just because HTML forms support that concept, does not mean that it's a useful one.

rajnish patel

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Posts: 56

posted 10 years ago

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First of all thank you for reply sir.
I know that there is no meaning of retrieving those values in text box but as I am in learning phase, I want to know that how to do it.....
It would be better if explain me how to do it.
Thank you once again for your reply.

Ulf Dittmer

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Posts: 43081

posted 10 years ago

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Please drop the habit of quoting entire posts. Quoting is for extracting specific bits of a previous posts that your reply references. Otherwise it makes no sense, and you should use the "Post reply" button instead. Notice how I used quoting in my previous post?

I did not say there was no meaning in putting values in the text box. I said there probably is no point in having a "clear form" button. If the objective is to learn, then there are much more important things for you to learn - for example, to structure your web app in such a way that there are no scriptlets in JSPs.

As to putting previously used input value into the form fields, are you familiar with the value attribute of the <input> tag that I mentioned? If not, that's what you should get started with. Once you know what that is and how it works, it should not be hard to add it to your JSP and populate it with the previous value should there be one. If you get stuck, come back here, tell us what you've learned, and how you tried to apply that, and we'll try to get you going again.

Niju Thomas

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Posts: 13

posted 10 years ago

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Ok first of all you have done some unnecessary things (You are in learning phase it is adjustable no problem :) ). If you need to show your value in text box you can do as below

<% long nm1 = Integer.parseInt(request.getParameter("num1")); %>

place this code first of your .jsp page

Then change your input field as

<input type="text" name="num1" onkeypress="return num(event)" value="<%=nm1 %>">

Please check with this.

rajnish patel

Ranch Hand

Posts: 56

posted 10 years ago