Issue
let me get straight to the point. I am using Spring Data JPA with QueryDSL in a project and I cannot figure out this myself.
I have the QueryDSL predicates in static methods that can take arguments and if the argument is not correct it should return "empty predicate" :
public static BooleanExpression byWhateverId(Long whateverId) {
if(whateverId == null) return [insert magic here];
// if parameter is OK return usual predicate
return QClass.property.whateverId.eq(whateverId);
}
Now I want to be able to chain these predicates using AND/OR oprators :
someRepository.findAll(byWhateverId(someParam).and(bySomethingElseId(1));
The problem here is that at this point I don't know whether 'someParam' is null or not (of course I can check but that's a lot of IFs). I also know I can use BooleanBuilder class but that seems also like a lot of code that should not be needed.
Does anybody knows what could be inserted instead of "[insert magic here]" ??? Or maybe I am missing something somewhere...
Thanks!
Solution
You can return null for non matching predicates in byWhateverId
and bySomethingElseId
and combine the predicate via ExpressionUtils.allOf()
In your case
Predicate where = ExpressionUtils.allOf(byWhateverId(someParam), bySomethingElseId(1));
someRepository.findAll(where);
Answered By - Timo Westkämper
Answer Checked By - Mildred Charles (JavaFixing Admin)