Venkat,
the getParameterValues method in fact does not throw a NullPointerException, when
parameter does not exist (no options selected), it just return null. So you could use
some code like this....
String[] prog=request.getParameterValues("prog_name");
if (prog == null) {
// Error handling stuff
}
Regards,
Enrique
-----Original Message-----
From: Venkat [mailto:[EMAIL PROTECTED]
Sent: Viernes, 14 de Marzo de 2003 05:43 a.m.
To: [EMAIL PROTECTED]
Subject: Re: Null pointer Exception while sending multiple list options
Hi,
Thanks for the info. I know that it return you a string array if they
selected and if not selected it return you a null.
But actually what i want to do is
User MUST select at least one values.This is a mandatory field.
I want to catch exception if user does'nt select any thing in server side.
Ok i can do it using client side but i am not relie completely on client
code.So i have to check in serverside as well.
Ok back to my problem if user doesn't selects any thing i am getting null
pointer exception and i want to catch this and do some prosses.
I got a work around.
Enumeration enum=reques.getParameterNames();
This will retrun you all the parameters
then by checking wether there is a parameter with the name prog_name i am
proceding further.
But i didn't understand why can't i catch the nullpointer when i used the
try catch block?
Thanks for any help
venkat
-----Original Message-----
From: A mailing list about Java Server Pages specification and reference
[mailto:[EMAIL PROTECTED] Behalf Of Francisco Manuel Mart�nez
Su�rez
Sent: Friday, March 14, 2003 3:57 PM
To: [EMAIL PROTECTED]
Subject: Re: Null pointer Exception while sending multiple list options
Loading values into a select field doesn�t set the value of it. So if the
user doesn�t choose anything, the onChange event is not sent to the select
field and when submit, the field prog_name has no value. I can�t remember if
not having value makes the field not to be included in the url as parameter.
But if no value is selected you can�t ask for them. Ask first for the
existence of the parameter, then for its values. Here is a reference for
that method in javax.servlet.ServletRequest interface.
REFERENCE________________________
getParameterValues
public java.lang.String[] getParameterValues(java.lang.String name)
Returns an array of String objects containing all of the values the
given request parameter has, or null if the parameter does not exist. For
example, in an HTTP servlet, this method returns an array of String objects
containing the values of a query string or posted form.
If the parameter has a single value, the array has a length of 1.
Parameters:
name - a String containing the name of the parameter whose value is
requested
Returns:
an array of String objects containing the parameter's values
See Also:
getParameter(java.lang.String)
<../../javax/servlet/ServletRequest.html>
> -----Mensaje original-----
> De: Venkat [SMTP:[EMAIL PROTECTED]
> Enviado el: viernes 14 de marzo de 2003 10:18
> Para: [EMAIL PROTECTED]
> Asunto: Null pointer Exception while sending multiple list options
>
> Hi all,
> I am sending multiple list options from one jsp to another.
>
> in my first jsp i am retrieving values from db and and displaying to user
> to
> select them.
> <SELECT NAME="prog_name" SIZE=3 MULTIPLE>
>
> while(rs.next()){
> String str=rs.getString("prog_name");
> out.println("<OPTION VALUE="+str+">"+str+"</OPTION>");
> }
> </select>
>
> I am retrieveing the selected (more than one or at least one)which user
> selects to my second jsp page
>
>
> try{
> String[] prog=null;
> prog=request.getParameterValues("prog_name");
> }catch(Exception e){}
>
>
> this works fine when user select at least one value.But if he doesn't
> selects anything
> i am getting null pointer exception.
>
> Can any one help me where i went wrong.
>
> Thanks in advance
> venkat
>
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