In one of the requirements we got to use a varchar field in db to store as number in UI. The user may specify + or - in the begining and it can be number up to 2 decimal places.
So, how to achieve this?
We are using jdev 220.127.116.11.2
may be have a transient field with number datatype and use af:convertNumber with minFractionDigits and maxFractionDigits to 2. it would take - not sure about + sign (might remove automatically). convert this as string and try saving it with your actual field.