Question:
view collection sorting in model layer ... good or bad?
I've been spending way too much time trying to sort a collection of
results from a datastore query. Today, I realized this might be the
responsibility of the view layer. Currently I have implemented the
sort in the compareTo method of my business object, as it implements
the Comparable interface. I have seen javascript libraries that
provide slick interfaces for sorting and filtering of collections. I
suspect this might also be managed by jstl or java scriptlets in my
JSP, though I don't know. I try to avoid java scriptlets in the JSP
to keep it clean. The sorting logic is a bit complicated. My users
want a weighted resultset. They have identified six cases, each with
a unique weight. I want to keep the business logic in the model layer
but the sorting is purely presentational.
My rookie question is this ... what is the optimal solution and why?
Answer:
Here are my thoughts on the matter:
I'm more in the domain driven philosophy boat. If your domain says that the
collection needs to be sorted, then in the model class what I do is model it
so that when the collection is retrieved within the model it is going to be
returned with the proper sort order, call this "default sort order". When
the need arises for a different sort order, the decision is made to either
make this the new sort order, or to extract out the sorting to make it more
flexible via a strategy or similar design pattern.
If sorting has nothing to do with the model, then I simply return it as is.
This then pushes the responsibility of sort order to the view layer. That
way, if you do ever have different views hitting the same model, you won't
be forcing the requirement of sorting upon each of them (though if each of
them do have the requirement maybe this is a hint that it should be part of
the model?)
Another valid option for setting a "default" sort order is to let the
database do the sorting when you first get the data. This isn't always
available though if you aren't populating from a database.
As you can see, there are lots of different ways to go about this. I
wouldn't say that any specific way is the "right" way.
