im starting with JPA2 and feel quite comfortbale so far. But I have a problem when persisting Entities with null property values for NON NULL database fields with default value.
I would like to be able to leave the entity property null and let the database insert the default value.
My current setup is openJPA with PostgreSQL.
I have this VERSION database table (Vorgabewert = Default value):
Spalte | Typ | Attribute
----------------+-----------------------------+----------------------------
status_ | smallint | not null Vorgabewert 0
time_ | timestamp without time zone | not null
system_time | timestamp without time zone | not null Vorgabewert now()
version | character varying(20) | not null
activationtime | timestamp without time zone |
importtime | timestamp without time zone |
I have an entity (Java DTO) which maps the database fields (except 'status') by xml configuration.
I hoped I could insert an entity without the system_time
set and expected that the database will fill the current time as default value.
JPA constructs the following SQL-Query:
INSERT INTO public.version (version, activationtime, importtime, system_time, time_) VALUES (?, ?, ?, ?, ?) [params=?, ?, ?, ?, ?]
and Postgres reacts with:
FEHLER: NULL-Wert in Spalte »system_time« verletzt Not-Null-Constraint
(sorry for German language but this message means the Not-Null-Constraint violation on 'system_time').
So what can I do? Is this a JPA or Database Problem. Can I configure JPA to exclude null properties from the INSERT SQL Statement.
I want to have the ability to set the 'system_time' in my entity or to let it be 'null' and let the database put the default value.
Any help is welcome!
Regads Klaus
I would not rely on default values in the database in conjunction with JPA. You would have to read the entity back after the insert otherwise you have a mismatch between the entity state and the db state.
Choose the pragmatic approach here and initialise all values in java. Never heard of a way to tell JPA/Hibernate to leave out null values in an insert/update.