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

user_248774 0
Viewed 138741

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

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

In my case, the status String can be null. I have debugged this and hibernate then generates an SQL string/query like this ....status = null... This however does not Work in MYSQL, as the correct SQL statement must be "status is null" (Mysql does not understand status=null and evaluates this to false so that no records will ever be returned for the query, according to the mysql docs i have read...)

My Questions:

  1. Why doesnt Hibernate translate a null string correctly to "is null" (and rather and wrongly creates "=null")?

  2. What is the best way to rewrite this query so that it is null-safe? With nullsafe I mean that in the case that the "status" String is null than it should create an "is null"?

null hibernate java
10 Answers

  1. I believe hibernate first translates your HQL query to SQL and only after that it tries to bind your parameters. Which means that it won't be able to rewrite query from param = ? to param is null.

  2. Try using Criteria api:

    Criteria c = session.createCriteria(CountryDTO.class);
c.add(Restrictions.eq("type", type));
c.add(status == null ? Restrictions.isNull("status") : Restrictions.eq("status", status));
List result = c.list();
user_2573810
user_212340

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)
}
user_2391680

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);
user_173430

Here is the solution I found on Hibernate 4.1.9. I had to pass a parameter to my query that can have value NULL sometimes. So I passed the using:

setParameter("orderItemId", orderItemId, new LongType())

After that, I use the following where clause in my query:

where ((:orderItemId is null) OR (orderItem.id != :orderItemId))

As you can see, I am using the Query.setParameter(String, Object, Type) method, where I couldn't use the Hibernate.LONG that I found in the documentation (probably that was on older versions). For a full set of options of type parameter, check the list of implementation class of org.hibernate.type.Type interface.

Hope this helps!

user_7856220
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