Re: [Wicket-user] is this approach correct?

Eelco Hillenius Wed, 02 Feb 2005 02:40:13 -0800

No, what I meant is that the converters were initially copied (and slightly altered) from the BeanUtils package. As they lacked the possibility of formatting (BeanUtils uses one-way converters only), I added support for formatting whilst not breaking the compatibility with BeanUtils by adding an optional interface for formatting. Now, this was for Baritus/ Maverick. For a large part I copied that into Wicket, as it was one of the things in Baritus that allways functioned well. However, for Wicket it would be best to have a clearer interface, thus having - just like JSF - converters for both ways.

This is the JSF interface:

public interface Converter
{
   Object getAsObject(FacesContext context,
                      UIComponent component,
                      String value) throws ConverterException;

   String getAsString(FacesContext context,
                      UIComponent component,
                      Object value) throws ConverterException;
}

Which is tightly coupled to JSF. Furthermore, I think (by doing a quick code scan of MyFaces) that locales are not supported in JSF as well as we support it.

Currently in Wicket, these are the interfaces:

public interface IConverter
{
   public Object convert(Object value);
}

and

public interface IFormatter
{
   public String format(Object value, String pattern);
}

Now, that I have a closer look to it, I think the pattern should be omitted, and the interface should look like:

public interface IConverter
{
   Object getAsObject(String value) throws ConversionException;

   String getAsString(Object value) throws ConversionException;
}

However, I know from experience that use of a pattern can be very convenient, I am have never been very happy with the way localization is implemented (which is again a legacy issue as I copied that from BeanUtils.

There are several ways to tackle this. I think the most elegant - and future safe - option is to introduce a context object, like:

public interface IConverter { Object getAsObject(ConversionContext ctx, String value) throws ConversionException;

String getAsString(ConversionContext ctx, Object value) throws ConversionException; }

Where ConversionContext would at least have a reference to the optional locale object to use (note that besides the user's locale, this can be explicitly set in the PropertyModel) and the optional conversion pattern. I think if the API looked like this, the writing of custom converters would be much simpler/ clearer and the lookup process would be drastically simplified and thus more transparent to our framework users.

What do you think?

Eelco

Juergen Donnerstag wrote:

So, as that's a legacy thing now, we could just as well loose the difference.
Sorry, it is probably only my english. Our current implementation
isn't better nore worse than what JSF (and may be others) offer. And
because there are "standard" packages out there to that job, the idea
is to move towards this package. Correct?
Juergen
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