I have beans being populated using constructor based queries as follows.

session.createQuery("select new someBean(someProp1 as abc, someProp2 as bcd, null as cde, someProp3 as cde)
from someEntity ").list();

Why should this throws a null pointer exception?

The DB2 database does not seem to support the following:
"select (cast(integerProp as string)) from someEntity"

This casting should be database specific, but where do we add this? unlike a dialect class where you can add new functions. I exepected the above hql: cast(integerProp as string) to work as:

sql: rtrim(cast(cast(integerProp as character(200)) as varchar(200))
which works correctly as a DB2 sql query.

rather than cast(integerProp as varchar) which throws a DB2 exception

WHERE DO WE OVERRIDE THIS CONVERSION FOR DB2?

Regards
Rama

Is there no way to do a select null as ?, this is very useful in populating constructor based entities using the hql:
"select new somePojo(entityAlias.prop1, null, entityAlias.prop3) from someEntity entityAlias"

How do I write my custom cast(integer as string) logic for DB2 dialect?

This was probably because the constructor data type (like BigDecimal) was expecting a non-null argument.

Solution: if someone were to use a constructor query and one of the columns has to be casted to big decimal, or if you want to override of the constructor arguments to a default big decimal value,

org.hibernate.type.BigDecimalType suggests that the getName() is big_decimal so the usage is

new entity(.., cast(0.0 as big_decimal))

else, expect "Unable to locate appropriate constructor"