Default value instead of NULL

schauder · **Joined:** Thu Jul 05, 2007 9:38 am **Posts:** 287

I am sure I have read somewhere that one can provide default value for Hibernate to provide for an attribute in case a null is found in the database. But I don't know how and I can't find the piece of documentation anymore.

Can anybody help with this?

Jens Schauder

danzone · **Joined:** Fri Aug 03, 2007 9:39 am **Posts:** 2

Usually you do the inverse thing: a null value set in the bean will be set in a default value in database.

You get this using default attribute within column element inside a property element:

Code:

<property name="property">
   <column name="PROPERTY_VALUE" default="..." />
</property>

Instead, if you want to set an attribute with a default value, in case in the database there is a null value in corresponding field, I think the best way is to modify your setter methods like this:

Code:

private final static Object DEFAULT_VALUE = ...;

private Object property;

public void setProperty(Object property) {
   if (property == null) {
        property = DEFAULT_VALUE;
   }
}

Pay attention that in this way, you cannot ever have a null value for your property: do you want this?

Daniele

Code:

schauder · **Joined:** Thu Jul 05, 2007 9:38 am **Posts:** 287

Hi daniele,
thanx for the effort, but this is not what I am looking for.

The setter thing is close, and it is what we are actually using right now. But the problem with this is, that Hibernate consideres this a change so the session becomes dirty and an update is caused.

The feature I am looking for was intended for legacy databases which might have a null value which really should some special instance. I am actually wondering if this could be used to avoid the problem of embeddable objects being null when all attributes are null.

(http://opensource.atlassian.com/project ... owse/HB-31)

prasadkarri · **Joined:** Wed Nov 19, 2008 2:04 pm **Posts:** 4

Hi,

I tried to configure default value sysdate for a date column.

<column name="xxx" default="sysdate"/>

when i ran the application it was not storing the sysdate in the column ?

Thanks in advance

schauder · **Joined:** Thu Jul 05, 2007 9:38 am **Posts:** 287

I don't see how this is an answer to my question ... don't know looks more like another question to me.

Anyway: AFAIK the default attribute sets a default value for the column in the database. At least with oracle this attribute is only used, when a insert statement doesn't specify any value for that column. But hibernate normally specifies a a value (NULL in case of doubt) to all columns, thus the default value never get used.

You can configure hibernate somehow to just update the columns that actually changed (I think), but I don't remember how, and I don't know if it applies to inserts.

Just set the attribute to the desired default value in your java code (e.g. in the constructor), or if you need the value from the database, set insertable and updatable to false. At least I think this should work.