Spring Boot JPA - find by 2 columns

I don't know how to create a JPA query to get all records from my table:

@Entity
@Table(name = "A")
public class A{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "message_id")
    private Message;

    @OneToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "user_id")
    private User user;
}

@Entity
@Table(name="message")
@Getter
@Setter
public class Message{

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(nullable = false, updatable = false)
    private Long id;

    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "account_id", foreignKey = @ForeignKey(name = "FK_account_to_message"))
    private Account account; //and then search by Account.id
}

SO I have 2 types of objects in A table (sometimes object is created from email, sometimes from a file):

1. one type without user_id (null) -> then I have to find all A object by searchning by Message -> Account -> Id
2. second type with user_id -> we can directly get A objects by values in user_id column

I want to get all records for specific user_id -> how to do that in most efficient way? I don't want to invoke 2 methods in repository:

 User user = userService.getEmail();
        List<A> aObjects= Stream.concat(ARepository.findByMessage_Account_Id(user.getId()).orElse(new ArrayList<>()).stream(),
                aRepository.findByUser_Id(user.getId()).orElse(new ArrayList<>()).stream()).collect(Collectors.toList());

Is it possible to create ONE repository method that finds all records for 2 different objects (one with user_id and second without user_id)?