I noticed as below if it is a string or char type defined in db there is a length attribute generated in hbm file. But I need length attribute for all numeric types as well for validation purpose. How can I achieve it in hbm2hbm in ant env.?

<property name="tankName" type="string">
<column name="tank_name" length="10" not-null="true">
<comment></comment>
</column>
</property>
<property name="capacity" type="java.lang.Short">
<column name="capacity" not-null="true">
<comment></comment>
</column>
</property>

numeric types have scale and precision.

Having length does not make sense.

But how come does timestamp have a length as below? In db for a numeric type you have to specify length or default one when creating it, for example mediumint(7). For timestamp type there isn't a length at all which makes sense to me.

<property name="deliveryTime" type="timestamp">
<column name="deliveryTime" length="19">
<comment></comment>
</column>
</property>

Methinks you are confusing length and precision. Numeric types have scale and precision, character types have length. The length on TIME, TIMESTAMP and DATEs is a holdover from the bad old days when those fields were stored in a table as character fields (DB/2 before v6 for example). The JDBC contract still states that the aforementioned fields should return a length.