How to validate the input field values before leaving the JSP page?

I set up a jsp page (say: first.jsp) with a couple of input-/entryfields in 
a form.
After the user entered some values he clicks on the submit button.
Normally (if all values are acceptable) the user should be forwarded to the 
next page (next.jsp).
If (and only then) the values are wrong the user should stay on the current 
page and some
error messages should appear at the top of current jsp.

Thus what I need is a code execution BEFORE leaving the current page and not
 (only) when the
page is created.

How do I implement this with JavaServerPages (under JBoss) ?
Unfortuantely there is no command like

<form action="if (validate(this.formdata)==true) next.jsp else first.jsp">

Arnold

apet10@hotmail.com (Arnold Peters) wrote in message news:<ckk5e8$dvp$03$1@news.t-online.com
>...
> I set up a jsp page (say: first.jsp) with a couple of input-/entryfields i
n a form.
> After the user entered some values he clicks on the submit button.
> Normally (if all values are acceptable) the user should be forwarded to th
e next page (next.jsp).
> If (and only then) the values are wrong the user should stay on the curren
t page and some
> error messages should appear at the top of current jsp.
>
> Thus what I need is a code execution BEFORE leaving the current page and n
ot (only) when the
> page is created.
>
> How do I implement this with JavaServerPages (under JBoss) ?
> Unfortuantely there is no command like
>
>  <form action="if (validate(this.formdata)==true) next.jsp else first.jsp"
>
>
> Arnold

perhaps something like this

<form onSubmit="return somevalidation(this)">