Spring Data JPA Specification Manyto One relationship - spring-data-jpa

Question

I have two entities in Spring Data JPA:
User--->* TaxPayment
The goal is to get the all the taxpayments related to user_id:
User.java
public class User extends AbstractAuditingEntity implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
..........
}
TaxPayment.jva
public class TaxPayment implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#NotNull
#Column(name = "payment_date", nullable = false)
private LocalDate paymentDate;
#NotNull
#Column(name = "amount", precision=10, scale=2, nullable = false)
private BigDecimal amount;
#Column(name = "reference")
private String reference;
#ManyToOne
private User user;
public Long getId() {
return id;
}..
}
I dont wan't to have oneTOMany Annotation from User.java and the column mapped in the Taxpayment as user_id.
Specification class as follows:
final class TaxPaymentSpecification {
private TaxPaymentSpecification(){
}
static Specification<TaxPayment> hasUser(Long userId){
return new Specification<TaxPayment>() {
#Override
public Predicate toPredicate(Root<TaxPayment> arg0, CriteriaQuery<?> arg1,
CriteriaBuilder arg2) {
// TODO Auto-generated method stub
Root<TaxPayment> root = arg0;
Subquery<Long> subqry = arg1.subquery(Long.class);
Root<User> user = subqry.from(User.class);
final Join<User,TaxPayment> taxpays = root.join("user");
subqry.select(taxpays.<Long> get("user_id"));
subqry.where(arg2.equal(user.<Long> get("id"),userId));
return arg2.in(arg0.get("user_id")).value(subqry);
}
};
}
}
Is specification is correct or wrong as per my goal to get all the TaxPayment related to user_id?

Answer 1

There is no need to use subquery if you already know the userId, which will be the value of user_id in TaxPayment table:
#Override
public Predicate toPredicate(Root<TaxPayment> arg0, CriteriaQuery<?> arg1,
CriteriaBuilder arg2) {
return arg2.equal(arg0.get("user_id"), userId);
}