problems with sorting API (i.e. ExtendedDataModel + Modifiable) that goes with
the rich:*dataTable components
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Key: RF-8269
URL: https://jira.jboss.org/jira/browse/RF-8269
Project: RichFaces
Issue Type: Bug
Security Level: Public (Everyone can see)
Components: component-tables
Affects Versions: 3.3.2.SR1
Reporter: Ian Springer
I recently tried to implement server-side sorting by implementing
ExtendedDataModel + Modifiable. I had several issues:
1) the name and usage of the Modifiable interface seem to assume that the
sorting will be done on the items from the currently loaded page of data (i.e.
"modifying" that in-memory list), but I think the more intuitive thing to do,
particularly for large data sets, is to sort the entire data set (e.g. using
ORDER BY if the data set is stored in a relational DB), and then return the
appropriate page from the sorted data set.
2) when I click on a sortable column header, modify() is called several times.
The first few times, the original/previous values of the SortField2s are passed
in, which serves no purpose. modify() should be called exactly once per
request, and the new sort fields and filter fields should be passed in.
Ideally, the same method would also support passing new page range settings.
3) The order of the items in the List<SortField2> is not at all intuitive - it
appears to be as follows:
- The items in the list are ordered in reverse precedence (i.e. they are
ordered from the lowest priority fields to the highest priority fields, with
the following exception:
If the last column clicked was already one of the sort fields (i.e. the
user has requested flipping that field from ASC->DESC or DESC-<ASC), the
corresponding SortField2 keeps its current position in the List, rather than
being moved to the end of the List, to signify it is now has the highest
precedence (as it should, for consistency sake)
It would be much more intuitive if the List was ordered by precedence, with the
highest priority fields first in the list, which is the same way sort fields
are ordered in an ORDER BY clause. Also, as described above, when toggling a
column between ASC and DESC, that column's should also be bumped up to the
highest precedence. Filter fields should also be ordered with the higher
precedence filters first in the list, rather than last.
If I were to revamp the paging/sorting/filtering API, I'd make it look
something like the following and stick it right in the ExtendedDataModel
interface:
void reloadData(List<FilterField> filterFields, List<SortField2> sortFields,
Range range)
This would allow the user of the API to load a new page of data with updated
filtering, sorting, and/or range in one swoop. The RF component impl would only
call this method if at least one of filterFields, sortFields, or range had been
changed by the GUI user since the last time reloadData() was called. It would
also call the method exactly once per request. This would save the implementer
of the interface from having to cache the previous values to track if any of
them had actually changed or if reloadData() had already been called for the
current request.
I'm attaching the implementation of ExtendedDataModel + Modifiable that I did
to prototype using them for the Red Hat RHQ project. It shows the various ugly
hacks I had to do to make the API work. Based on the prototype, we have decided
to stick with custom components and facets we have been using, rather than
using the sorting support currently provided by rich:dataTable and
rich:extendedDataTable. I hope the issues I've described in this JIRA can be
addressed, so we can switch over to using pure RichFaces.
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