How to initialize Specification of Spring Data JPA?

Question

I have a method that does a search with filters, so I'm using Specification to build a dynamic query:

public Page<Foo> searchFoo(@NotNull Foo probe, @NotNull Pageable pageable) {

        Specification<Foo> spec = Specification.where(null);  // is this ok?

        if(probe.getName() != null) {
            spec.and(FooSpecs.containsName(probe.getName()));
        }
        if(probe.getState() != null) {
            spec.and(FooSpecs.hasState(probe.getState()));
        }
        //and so on...

        return fooRepo.findAll(spec, pageable);
}

There is the possibility that there are no filters specified, so I would list everything without filtering. So having that in mind, how I should initialize spec ? Right now, the code above doesn't work as it always returns me the same result: all the registers of the table, no filtering have been aplied althought and operations have been made.

FooSpecs:

public class PrescriptionSpecs {

    public static Specification<Prescription> containsCode(String code) {
        return (root, criteriaQuery, criteriaBuilder) ->
            criteriaBuilder.like(root.get(Prescription_.code), "%" + code + "%");
    }

    // some methods matching objects...
    public static Specification<Prescription> hasContractor(Contractor contractor) {
        return (root, criteriaQuery, criteriaBuilder) ->
            criteriaBuilder.equal(root.get(Prescription_.contractor), contractor);
    }
    //... also some methods that access nested objects, not sure about this
    public static Specification<Prescription> containsUserCode(String userCode) {
        return (root, criteriaQuery, criteriaBuilder) ->
            criteriaBuilder.like(root.get(Prescription_.user).get(User_.code), "%" + userCode + "%");
    }
}

Trisa

What kind of exception do you get? I think this should work. Please add the stack trace. Also, why do you ask "is this ok?" if you already know "the code above doesn't work" – Fovea

@JensSchauder There is no error but it doesn't filter. I'm getting all the results of the table, always. I ask if its is ok because I'm not sure if it is, I didn't see an example like this. Moreover, when I debug, i see spec empty. – Trisa

I see. Can you share the code for FooSpecs? – Fovea

updated with FooSpecs (aka PrescriptionSpecs) – Trisa

Hmm, looks ok to me. Do they work on their own, like in fooRepo.findAll(containsUserCode("XXX"), pageable);? – Fovea

No, for now I only have this method (searchFoo). So doing Specification.where(null) is legit? I'm worried why while debuging I dont see the content ofspec, the IDE is saying it's null. – Trisa

Let us continue this discussion in chat. – Fovea

Answer 1

Specification.where(null) works just fine. It is annotated with @Nullable and the implementation handles null values as it should.

The problem is that you are using the and method as if it would modify the Specification, but it creates a new one. So you should use

spec = spec.and( ... );

Fovea

Let's say I have 5 fields, but because they all are null, the spec is left with the value of Specification.where(null). Question: is there a way to check that spec equals to Specification.where(null) – Courtund

@IlyaSerebryannikov please don't ask new questions in comments, ask them in questions. – Fovea