This is an interesting question. I'll give you my take on it -- others
will have different opinions.
On Wed, 13 Jun 2001, Jonathan Asbell wrote:
> Hello all. I wanted to know where you are doing type conversion. The
> reason I ask is because to some extent one may choose to do slightly
> deeper validations in the ActionForm for reasons of expectation. The
> question remains as to the exact level of "light" validation we should
> do in the ActionForm. From reading the list it seems the general
> consensus is to only do validation of a value's existance. However,
> where do you do type conversion then? In the ActionForm? In the
> Action? In the BusinessObject layer? The issues are:
>
> 1) If I do it in the ActionForm and there is a problem in the Action,
> then I have to reconvert back to a String on the way back.;
>
That's why I advocate that properties in an ActionForm should be Strings
instead of dates/ints/whatever.
However, this is an issue that the validate() method can check, to catch
things as early as possible. Whether you actually save the converted
value here or not is a compute-time-versus-memory-space tradeoff, and
either solution is possible.
> 2) If I do it in the Action, same problem, but also the argument has
> been brought to my attention that the ActionForm bean (although
> temporary) does not truly represent the data it contains (like when a
> value represents a double, money, or a Date)
>
If you're using an ActionForm bean that uses validation (the default
case), and if your validate method checks for any type conversion
problems, then the Action can assume that the conversion will not
fail. Of course, you need an "it can't happen, but it did" sort of error
catch for conversion errors when you copy the String versions of the
properties to your actual business objects, but 99% of the time they won't
actually get triggered.
> 3) If I do it in the Business Layer than the message has gone deeper
> into the application than necessary which sacrifices performance and
> needless use of resources.
>
Type conversion errors should have been caught by now. Business objects
should deal with the native property types -- part of the role of the
Action is to be an adapter between the String representation (used by the
form beans) and the native representation (used by the business logic).
Craig McClanahan
