During the processing of a request initiated by changing the filter (selecting another option in a dropdown) of a column, the transmitted value is set to lower case in

FilterState:53 ([...] saveState(filteredColumn, params.get(filteredId).toLowerCase()) [...])

This affects showing the selected option after rendering the updated table, as due to comparison mismatch always the first option available is shown but not the selected one.

While rendering the response DataTableHeadRenderer:375 does the comparison based on the select items (having their values in original case, while the transmitted value has been set to lower case).

I am not sure what class is in charge to set the value to lower case, but from my point of view it could be left to the implementations of FilterConstraint as it enables for having additional filters such as

* startsWithIgnoreCase
* endsWithIgnoreCase
* exactIgnoreCase

or to avoid breaking existing behaviour something like startsWithConsiderCase.