Spring. How to get an entity with a specific field value?

Question

Java

Hello!
I have a House, which has a bunch of other child entities, including Docs. The problem is that there are documents of several different types. Right now I only want to work with one particular one, but I will need more in the future.
The database already has data for other types and, of course, the form crashes when you try to open it - after all, more than 1 result is returned. I changed the connection to ManyToOne, in House I made a List instead of a single value.
But I don’t understand where and how to separate the unnecessary ones. Now the code looks like this:
HOUSE

@Data
@Entity
@Table(schema = "public", name = "House")
public class House implements Serializable {

    @Column(name = "House_ID")
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

// всякие другие поля дома и другие дочерние сущности

    @OneToMany(mappedBy = "house", cascade = CascadeType.ALL, fetch = FetchType.LAZY, orphanRemoval = true)
    @Cascade(org.hibernate.annotations.CascadeType.ALL)
    private List<HouseDoc> houseDocs;

HouseDoc

@Entity
@Table(name = "House_Doc", schema = "public")
@Data
public class HouseDoc implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "Pkey_id")
    private Integer id;

    @Column(name = "Doc_type")
    private int docType;

// всякие другие поля документов

   @ManyToOne
    @JoinColumn(name = "House_ID", referencedColumnName = "House_ID")
    protected House house;
}

dto house

@Data
@NoArgsConstructor
@AllArgsConstructor
public class HouseFullProjection extends HouseProjection {
  private List<HouseDoc> houseDocs;

dto HouseDoc

@Data
public class HouseDocProjection implements Serializable {
    private Integer id;
    protected int docType;
}

Controller: trying to give everything to the interface

@RequestMapping(value = "/houses/edit/{id}")
    public ModelAndView editCard(@PathVariable("id") Integer id) {
        House house = service.getHouse(id);
        house.getWindowOptions(); // это всякие другие дочерние сущности, с ними всё ок
        <b>house.getHouseDocs();</b> // вот тут мне нужен 1 документ, а не пачка
        return editCard(house);
    }

Please tell me where it will be correct to insert the condition: only documents with docType = 1 are needed.

Answer 1

Hello!
Why don't you use jpql (jpa) capabilities?
I don't see all your code, in particular @Service & @Repository
Approximately, you need to do something like this...
Add to the repository

@Query(SELECT House h FROM ... WHERE h.housId = ?1 AND h.housedoc.docType = ?2)
House findHouseByIdAndHouseDocByDocType(Long houseId, int docType)

Of course, this needs to be corrected ... but in general, something like this
A in service implement a method that takes Long & int as arguments and returns the House entity.