当关系为 null 时，JPA 规范不起作用

Question

I'm implementing a search based on two entities.

@Entity(name = "user")
public class UserEntity {
    @Id
    @GeneratedValue(generator = "system-uuid")
    @GenericGenerator(name = "system-uuid", strategy = "uuid")
    @Column(updatable = false, nullable = false)
    private String id;
    @Column(unique = true, nullable = false)
    private String email;
    @OneToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "foo_id", referencedColumnName = "id")
    private FooEntity foo;
    private UserType type;
}

@Entity(name = "foo")
public class FooEntity {
    @Id
    @GeneratedValue(generator="system-uuid")
    @GenericGenerator(name="system-uuid", strategy = "uuid")
    @Column(updatable = false, nullable = false)
    private String id;
    private String identifier;
}

Now I want to look for users based on email adres OR when the FooEntity relation exist based on the identifier in that relationship. AND based on the enum type in the UserEntity.

I tried with following query:

public static Specification<UserEntity> emailLike(String text) {
     return (root, query, criteriaBuilder) -> criteriaBuilder.like(root.get("email"), "%" + text + "%");
    }
    
public static Specification<UserEntity> patientIdentifier(String text) {
      return (root, query, criteriaBuilder) -> criteriaBuilder.like(root.join("foo").get("identifier"), "%" + text + "%");
    }
public static Specification<UserEntity> userType(UserType type) {
            return (root, query, criteriaBuilder) -> criteriaBuilder.equal(root.get("type"), type);
        }
    
final Specification<UserEntity> specification = Specification.where(
                UserSpecification.patientIdentifier(text)
                        .or(UserSpecification.emailLike(text))
        ).and(
                UserSpecification.userType(type)
        );
    
final Page<UserEntity> userEntities = userRepository.findAll(specification, pageable);

Now this query seems to work when the relationship with the FooEntity exists. When this relationship is null nothing is returned even when the email and type matches.

Can someone help me out?

Answer 1

You shouldn't just join but left join or right join. A join is an inner join which means it only matches records which match the join criteria. Anything equals null in SQL is always false, so I'd either of the join sites is null, the record isn't in the result set. So a left join says, respond with all of the left site entities and match the right site only if present, if not right site is null.

So join should look like root.join("foo", JoinType.LEFT) (not tested)