Dynamic combination of multiple PredicateSpecification with JpaSpecificationExecutor with Micronuat data for MongoDB

Question

How can I append all the PredicateSpecification or QuerySpecification using JpaSpecificationExecutor in MongoDB with Micronaut data?

Predicate

public class DiscountSpecification {
    final static BeanIntrospection<Discount> introspection = BeanIntrospection.getIntrospection(Discount.class);
    static String[] discountProperty = introspection.getPropertyNames();

    public static PredicateSpecification<Discount> DiscountIdEquals(ObjectId DiscountId) {
        return (root, criteriaBuilder) -> criteriaBuilder.equal(root.get(discountProperty[0]), DiscountId);
    }

    public static PredicateSpecification<Discount> DiscountCodeEquals(String DiscountCode) {
        return (root, criteriaBuilder) -> criteriaBuilder.equal(root.get(discountProperty[1]), DiscountCode);
    }
}

Now based on the condition I want to append all the predicate

@Introspected
public record QueryBuilderSpecification() {
    public static PredicateSpecification<Discount> QueryBuilder(DiscountFilterModel discountFilterModel){
        PredicateSpecification<Discount> predicateSpecification = null;

        if (discountFilterModel.getId() != null){
            predicateSpecification =  DiscountIdEquals(new ObjectId(discountFilterModel.getId()));
        }
        if (discountFilterModel.getDiscountCode() != null){
            predicateSpecification =  DiscountCodeEquals(discountFilterModel.getDiscountCode());
        }
        return predicateSpecification;
    }
}

The above code doesn't append for both the condition. Quite not sure how to combine both if both are present.

Answer 1

It should be possible to use DiscountIdEquals(...).and(DiscountCodeEquals(..)).

Your example can be used with PredicateSpecification.ALL as the initial state and then have:

predicateSpecification = predicateSpecification.and(DiscountIdEquals(...)).

There are some examples in the test apps: https://github.com/micronaut-projects/micronaut-data/blob/master/doc-examples/mongo-example-java/src/test/java/example/PersonRepositorySpec.java#L50

Answer 2

Based on the code PredicateSpecification you can and & or specifications together. As demonstrated in the Micronaut Data User Guide