validation on JSP page does not work
Question
I have the following jsp page with one input textbox, upon entering the number, the page is redirected to a servlet where I retrieve that number and let's say display it on a page. I'm trying to do the validation in JavaScript but in spite of it, it's still executing the servlet even though validation returns false and I get java.lang.NumberFormatException: For input string: "" in the doGet method on the servlet on the following line: int max = Integer.parseInt(request.getParameter("lengthTxt")); . Why does it seem to bypass validation and still execute the servlet ? How to fix it ? thanks for help !
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<script>
function validateForm()
{
if(document.frm.lengthTxt.value=="")
{
alert("Number should not be left blank");
document.frm.lengthTxt.focus();
return false;
}
}
</script>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Length calc</title>
</head>
<body>
<h3>enter length</h3>
<form name=frm action="MyServlet" onSubmit="return validateForm();">
<input name="lengthTxt" />
<br>
<br>
<input type = "submit" value = "Submit"/>
</form>
</body>
</html>
2 answers
solution1
0 2014-12-11 14:05:32
This seems insane.After checking this code on some browsers.It will execute form submit event even the the onsubmit returned with a false value like this.
onsubmit="return validateForm()";
So that you can prevent further form exection with event.preventDefault() function.
So that using Conditional Statement in onsubmit will save the day.Below goes the full statement to be used.
<form onsubmit="event.preventDefault(); return validateMyForm();">
Anything more,jz comment.
solution2
0 ACCPTED 2014-12-16 11:31:13
if you given wrong name in field to focus then it happens otherwise it should be work fine. please check again in java Script function.
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