Hibernate version:3.0
Name and version of the database: HSQLDB, Firebird

Here is a part of the mapping:
<joined-subclass name="filters.AgeFilter">
<key column="ID"/>
<component name="interval" access="field">
<property name="minValue" access="field"/>
<property name="maxValue" access="field"/>
</component>
</joined-subclass>


If both minValue and maxValue are NULL then hibernate sets interval to NULL.
How this can be avoided . I have real case where all properties may be null but the component class must be instantiated. Even if I cteate it on the empty constructor Hibernate later sets it to null.

Yes, this is explciitly covered in the docs.

For the behavior you suggest, use a custom type.

Well my class is

Interval<T extends Comparable>
T minValue;
T maxValue;
....

making a custom type for every kind of instances (Integer, Long, Date, etc) is not very nice solution. I have a temporary hack do deal with the problem - it is not a stopper for me. Can you tell me why Hibernate does not to make instance of the component object when all properties are null, or direct me to some docs where I can read about it. And why there is no setting to change this behaviour.

thank you