Spring Projections 不返回状态详细信息

Question

我有一个已与 Spring Data JPA 集成的 Country 和 State 表。我在 CountryServiceImpl 中创建了一个函数public Page<CountryDetails> getAllCountryDetails，用于获取所有国家和相应的国家详细信息。该服务运行良好，并为我提供以下输出：

{
  "content": [
    {
      "id": 123,
      "countryName": "USA",
      "countryCode": "USA",
      "countryDetails": "XXXXXXXX",
      "countryZone": "XXXXXXX",
      "states": [
        {
          "id": 23,
          "stateName": "Washington DC",
          "countryCode": "USA",
          "stateCode": "WAS",
          "stateDetails": "XXXXX",
          "stateZone": "YYYYYY"
        },
        {
          "id": 24,
          "stateName": "Some Other States",
          "countryCode": "USA",
          "stateCode": "SOS",
          "stateDetails": "XXXXX",
          "stateZone": "YYYYYY"
        }
      ]
    }
  ],
  "last": false,
  "totalPages": 28,
  "totalElements": 326,
  "size": 12,
  "number": 0,
  "sort": null,
  "numberOfElements": 12,
  "first": true
}

我的完整代码如下：

CountryRepository.java

@Repository
public interface CountryRepository extends JpaRepository<CountryDetails, Integer> {

    @Query(value = "SELECT country FROM Country country GROUP BY country.countryId ORDER BY ?#{#pageable}", 
    countQuery = "SELECT COUNT(*) FROM Country country GROUP BY country.countryId ORDER BY ?#{#pageable}")
    public Page<CountryDetails> findAll(Pageable pageRequest);
}

CountryServiceImpl.java

@Service
public class CountryServiceImpl implements CountryService {

    @Autowired
    private CountryRepository countryRepository;

    @Override
    public Page<CountryDetails> getAllCountryDetails(final int page, final int size) {
        return countryRepository.findAll(new PageRequest(page, size));
    }
}

CountryDetails.java

@Entity
@Table(name = "country", uniqueConstraints = @UniqueConstraint(columnNames = "id"))
public class CountryDetails {

    @Id
    @GeneratedValue
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;
    private String countryName;
    private String countryCode;
    private String countryDetails;
    private String countryZone;

    @JsonManagedReference
    @OneToMany(fetch = FetchType.LAZY, mappedBy = "countryDetails")
    private List<State> states;

    // getters / setters omitted
}

State.java

@Entity
@Table(name = "state", uniqueConstraints = @UniqueConstraint(columnNames = "id"))
public class State {

    @Id
    @GeneratedValue
    @Column(name = "id", unique = true, nullable = false)
    private Integer id;
    private String stateName;
    private String countryCode;
    private String stateCode;
    private String stateDetails;
    private String stateZone;

    @JsonBackReference
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "countryCode", nullable = false, insertable = false, updatable = false, foreignKey = @javax.persistence.ForeignKey(name="none",value = ConstraintMode.NO_CONSTRAINT))
    private CountryDetails countryDetails;

    // getters / setters omitted
}

现在的问题

实际上，我希望国家/地区服务以最少的信息返回，如下所示

{
  "content": [
    {
      "countryName": "USA",
      "countryCode": "USA",
      "states": [
        {
          "stateCode": "WAS"
        },
        {
          "stateCode": "SOS"
        }
      ]
    }
  ],
  "last": false,
  "totalPages": 28,
  "totalElements": 326,
  "size": 12,
  "number": 0,
  "sort": null,
  "numberOfElements": 12,
  "first": true
}

为了实现这一点，我使用了如下所示的投影

CountryProjection .java

public interface CountryProjection {
    public String getCountryName();
    public String getCountryCode();
    public List<StateProjection> getStates();
}

StateProjection .java

public interface StateProjection {
    public String getStateCode();
}

CountryServiceImpl.java

@Repository
public interface CountryRepository extends JpaRepository<CountryDetails, Integer> {

    @Query(value = "SELECT country.countryName AS countryName, country.countryCode AS countryCode FROM Country country GROUP BY country.countryId ORDER BY ?#{#pageable}", 
    countQuery = "SELECT COUNT(*) FROM Country country GROUP BY country.countryId ORDER BY ?#{#pageable}")
    public Page<CountryProjection> findAll(Pageable pageRequest);
}

但现在服务正在返回如下所示的任何状态详细信息

{
  "content": [
    {
      "countryName": "USA",
      "countryCode": "USA"
    }
  ],
  "last": false,
  "totalPages": 28,
  "totalElements": 326,
  "size": 12,
  "number": 0,
  "sort": null,
  "numberOfElements": 12,
  "first": true
} 

我们怎样才能得到最小的状态细节，如下所示

{
  "content": [
    {
      "countryName": "USA",
      "countryCode": "USA",
      "states": [
        {
          "stateCode": "WAS"
        },
        {
          "stateCode": "SOS"
        }
      ]
    }
  ],
  "last": false,
  "totalPages": 28,
  "totalElements": 326,
  "size": 12,
  "number": 0,
  "sort": null,
  "numberOfElements": 12,
  "first": true
}

谁能帮我解决这个问题

Answer 1

您可以让您的 CountryService 返回一个 DTO，而不是只包含您需要的字段的实体。

服务

@Service
public class CountryServiceImpl implements CountryService {

    @Autowired
    private CountryRepository countryRepository;

    @Override
    public Page<CountryDetailsDto> getAllCountryDetails(final int page, final int size) {
        return countryRepository.findAll(new PageRequest(page, size))
                .map(c -> {
                    CountryDetailsDTO dto = new CountryDetailsDTO();
                    dto.setCountryCode(c.getCountryCode());
                    dto.setCountryName(c.getCountryName());

                    dto.setStates(c.getStates().stream().map(s -> {
                        StateDto stateDto = new StateDto();
                        stateDto.setStateCode(s.getStateCode());

                        return stateDto;
                    }).collect(Collectors.toSet()));

                    return dto;
                });
    }
}

DTO

public class CountryDetailsDTO {

    private String countryName;

    private String countryCode;

    private Set<StateDto> states;
}

public class StateDto {

    private String stateCode;
}

Answer 2

尝试将 JsonIgnore 与返回 JSON 中不需要的字段一起使用

@JsonIgnore
private String stateDetails;

Answer 3

您可以将transient 关键字与json 中不需要的变量一起使用。

否则使用

@Expose String myString;

Answer 4

第一个想法

IMO 你做事的方式有些不对劲。我不明白你为什么要这样直接定义查询：

@Query(value = "SELECT country.countryName AS countryName, country.countryCode AS countryCode FROM Country country GROUP BY country.countryId ORDER BY ?#{#pageable}", 
    countQuery = "SELECT COUNT(*) FROM Country country GROUP BY country.countryId ORDER BY ?#{#pageable}")

基本上就是通过select创建一个投影。

另一方面，您正在使用 Interface-based Projections 再次进行投影，但通过公开您想要投影的属性的吸气剂。据我所知，您通过接口很好地定义了层次结构，它应该是有效的方法。

所以我要问的是，您是否尝试过将@Query 部分全部删除？

第二个想法（在评论中）

另一个想法可以是在jpql 中使用join fetch construct，它用于告诉休眠以通过查询热切地加载关联。

@Query(value = "SELECT country.countryName AS countryName, country.countryCode AS countryCode, countryStates FROM Country country join fetch country.states countryStates GROUP BY country.countryId ORDER BY ?#{#pageable}"

Answer 5

您可以查看注释的文档：

@JsonIgnoreProperties("字段名")

此注释需要在您的案例 Country*、State* 中应用于您的 POJO 类，提及您不需要成为响应的一部分的字段的逗号分隔列表。

您可以尝试这种方法，而不是更改为投影样式的实现。

@JsonIgnoreProperties({ "id","countryDetails","countryZone"})
public class CountryDetails

@JsonIgnoreProperties({ "id","stateName","countryCode","stateDetails","stateZone"})
public class State