[FIXED] Create Spring Data Jpa Specification method without JOINS

Issue

I have a Spring-MVC online-store project where I use Spring Boot and Hibernate. I decided to use the Specification for filtering. Thus, I wrote a method for the specification using JOINS. Please, tell me how you can write the same method without JOIN.

TeaSpecification class:

public static Specification<Tea> getTeasByFilter(Long colorId, Long typeId, Long countryId) {
        return (root, query, criteriaBuilder) -> {
            Join<Object, Object> colorJoin = root.join(Tea_.TEA_COLOR);
            Join<Object, Object> typeJoin = root.join(Tea_.TEA_TYPE);
            Join<Object, Object> countryJoin = root.join(Tea_.COUNTRIES);
            Predicate countryPredicate = criteriaBuilder.equal(countryJoin.get(Countries_.ID), countryId);
            Predicate colorPredicate = criteriaBuilder.equal(colorJoin.get(TeaColor_.ID), colorId);
            Predicate typePredicate = criteriaBuilder.equal(typeJoin.get(TeaColor_.ID), typeId);
            return criteriaBuilder.and(colorPredicate, typePredicate, countryPredicate);
        };
    }

Drink class(Tea extends Drink):

@Inheritance(strategy = InheritanceType.JOINED)
public class Drink {

    // Fields
    //
    private @Id
    @GeneratedValue
    Long id;

    private String name;

    private BigDecimal price;

    private String about;

    @Column(name = "is_deleted")
    private boolean isDeleted;

    // Relationships
    //
    @ManyToOne
    @JoinColumn(name = "packaging_id")
    private Packaging packaging;

    @ManyToOne
    @JoinColumn(name = "manufacturer_id")
    private Manufacturer manufacturer;

    @ManyToOne
    @JoinColumn(name = "country_id")
    private Countries countries;
}

public class Tea extends Drink {

    // Relationships
    //
    @ManyToOne
    @JoinColumn(name = "type_id")
    private TeaType teaType;

    @ManyToOne
    @JoinColumn(name = "color_id")
    private TeaColor teaColor;
}

Solution

public class TeaSpecification {

    public static Specification<Tea> getTeasByFilter(Long colorId, Long typeId, Long countryId) {
        return (root, query, criteriaBuilder) -> {
            Predicate colorPredicate = criteriaBuilder
                    .equal(root.get(Tea_.teaColor).get(TeaColor_.id), colorId);
            Predicate typePredicate = criteriaBuilder
                    .equal(root.get(Tea_.teaType).get(TeaType_.id), typeId);
            Predicate countryPredicate = criteriaBuilder
                    .equal(root.get(Tea_.countries).get(Countries_.id), countryId);
            return criteriaBuilder.and(colorPredicate, typePredicate, countryPredicate);
        };
    }
}

Answered By - Artur Vartanyan