Re: Validating form inputs?

From:

Daniel Pitts <newsgroup.nospam@virtualinfinity.net>

Newsgroups:

comp.lang.java.help

Date:

Wed, 21 Mar 2012 12:59:29 -0700

Message-ID:

<Bqqar.4635$Ce4.4160@newsfe21.iad>

On 3/21/12 12:02 PM, Davej wrote:

On Mar 20, 2:50 pm, Lew<lewbl...@gmail.com> wrote:

Daniel Pitts wrote:

Davej wrote:

I have been thinking about the way I have been validating form
inputs in the servelet [sic] and wonder if I would be much
better off using class methods to verify these inputs?

What exactly do you mean by "class methods"? Do you mean 'static'
member methods?

Consider that I am almost always gathering the inputs to
instantiate one or more objects, but I gather and validate
-- and then instantiate. Maybe I should instantiate an empty
object and then use class methods to validate the inputs?

Maybe. It depends on what you mean by "class methods".

Why? I think it could be done either way. If it was a static method is
would be made generic. If it was non-static it could be an alternate
set method...

public String ValidateAndSetQuiz1(String q1) //returns error message
{
   double score;

   try{
      score = Double.parseDouble(q1);
      if ( score< 0 || score> 100.0)
         return "Value out of allowed range";

   }catch (Exception e)
   {
      return "Value is non-numeric";
   }

   m_quiz1 = score; //accept and set instance variable m_quiz1
   return null; //signifies that submitted value was accepted
}

Augh, no.

The setter should throw an exception if the value isn't valid. Also, a
setter should take in a correctly typed parameter, not a string to be
parsed.