Hibernate: How to set NULL query-parameter value with HQL?

Question

How can I set a Hibernate Parameter to \"null\"? Example:

Query query = getSession().createQuery(\"from CountryDTO c where c.status = :status  and c.type =:t         


        

Answer 1

I did not try this, but what happens when you use :status twice to check for NULL?

Query query = getSession().createQuery(
     "from CountryDTO c where ( c.status = :status OR ( c.status IS NULL AND :status IS NULL ) ) and c.type =:type"
)
.setParameter("status", status, Hibernate.STRING)
.setParameter("type", type, Hibernate.STRING);

Answer 2

It seems you have to use is null in the HQL, (which can lead to complex permutations if there are more than one parameters with null potential.) but here is a possible solution:

String statusTerm = status==null ? "is null" : "= :status";
String typeTerm = type==null ? "is null" : "= :type";

Query query = getSession().createQuery("from CountryDTO c where c.status " + statusTerm + "  and c.type " + typeTerm);

if(status!=null){
    query.setParameter("status", status, Hibernate.STRING)
}


if(type!=null){
    query.setParameter("type", type, Hibernate.STRING)
}

Answer 3

HQL supports coalesce, allowing for ugly workarounds like:

where coalesce(c.status, 'no-status') = coalesce(:status, 'no-status')

Answer 4

The javadoc for setParameter(String, Object) is explicit, saying that the Object value must be non-null. It's a shame that it doesn't throw an exception if a null is passed in, though.

An alternative is setParameter(String, Object, Type), which does allow null values, although I'm not sure what Type parameter would be most appropriate here.