Update 2: Code for Custom Converter that helps work around the problem
I reported this to IBM today (my first Service Request). I thought I should share the bugs, so others are aware of it.
Bug with multi-value fields and converters in XPages
By multi-value field, I mean a field that have the multi-value
When saving a multi-value field of type String, the value alternates
between being split into multi-value, and being a flat string.
First save -> multi-value
Second save -> flat string
Third save -> multi-value
When saving a multi-value field of type date or number, the field only saves
the first value.
I also tried using a custom converter to modify the field
(getAsObject -> split, getAsString -> join). This doesn't work at all.
It seems custom converters only can be result in string values.
How hard can it be to implement multi-value. It seems like someone slapped together a couple of lines of code, and forgot to test it. I'm surprised that there isn't any other bloggers haven't written about this. Maybe multi-value fields aren't that popular?