Does hibernate convert column != null in HQL to a column is null in SQL?
If you do want to use null values with '=' or '<>' operators you may find the
answer from @egallardo hier
very useful.
Short example for '=': The expression
WHERE t.field = :param
you refactor like this
WHERE ((:param is null and t.field is null) or t.field = :param)
Now you can set the parameter param either to some non-null value or to null:
query.setParameter("param", "Hello World"); // Works
query.setParameter("param", null); // Works also