Re: Formatting a date

On Mon 27 March 2006 17:36, Keats Kirsch wrote:
> >I'll also look at making $Text.formatDate cache the SimpleTextFormat
> > objects that it creates and run some profiling to see whether or not this
> > is really an advantage...
>
> Yes the formatDate() method was kind of a quick hack.  At one point I
> had written a DateTool, but I never got it clean enough to commit to CVS
> (and now I've lost it).  Perhaps I'll give it another whack.  It's
> actually fairly complicated, given all the different date formats and
> localization etc.  It would be nice if the tool could pick up the locale
> from the request, but then it would be Servlet specific.  But something
> simple would probably be useful for parsing and formatting dates.

In the meantime, adding something like this to TextTool will help:-

private final static Map __simpleDateFormats = new HashMap();
public static String formatDate (Date date, String format)
{
  SimpleDateFormat formatter = null;
  synchronized (__simpleDateFormats) {
    formatter = (SimpleDateFormat) __simpleDateFormats.get(format);
    if (formatter == null) {
      formatter = new SimpleDateFormat(format);
      __formatters.put(format, formatter);
    }
  }
  return formatter.format(date);
}

I'll run some tests and see if it is worth the added complexity from a 
performance viewpoint.

> I'm thinking a factory that would produce date wrappers.  E.g.,
>
> #set $dt = $DateFactory.parse("27-Mar-2006", "dd-MMM-yyyy")
> #set $dt.Format.Short = "MM/dd/yyyy"
> #set $dt.Format.Default = "dd-MMM-yyyy"
>
> Default format: $dt                      ==> 27-Mar-2006
> Short format: $dt.Format.Short   ==> 02/27/2006
>
> #set $dt = $dt.addMonths(1)
> New date: $dt    ==> 27-Apr-2006

Why not make it so that the wrapper class extends Date so that you can then 
also used the wrapped class as a drop-in replacement for Date in other 
methods.

Also, why not make the wrapper include a hashtable accessor that enables you 
to extend the number of registered formats on it?

e.g.

$DateFactory.registerFormat("Short", "MM-dd-yyyy")
#set $dateWrapper = $DateFactory.parse("27-Mar-2006", "Short")
$dateWrapper.Time --> java.util.Date.getTime()
$dateWrapper.Short --> DateWrapper.get("Short") --> String (by querying 
DateFactory for the SimpleDateFormatter registered as "Short" and then 
formatting itself using this format)

If I was really looking for flexibility you could also make cascading parsers 
which would let you do things like this:-

$DateFactory.registerFormat("Long", "hh:MM:ss MM-dd-yyyy")
$DateFactory.registerFormat("Medium", "hh:MM MM-dd-yyyy")
$DateFactory.registerFormat("Short", "MM-dd-yyyy")
#set $dateWrapper = $DateFactory.parse("22-05-1971")

and it would iterate through the registered formatters in order finding one 
that can parse the supplied text...

<snip>

Alex


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