Java Spring Data JPA and REST API: exclude fields of nested JSON object

Question

Currently I'm using Spring Data JPA 2.2.1 with a Spring Boot Web 2.2.1 for a REST API service.

A getter call to /categories returns the following JSON, which in fact is the desired result:

[
    {
        "category1": "A",
        "category2": "B",
        "subcategories": []
    },
    {
        "category1": "A",
        "category2": "B",
        "subcategories": [{
                "field1": "A",
                "field2": "B",
                "field3": "C",
                "field4": "D"
        }]
    },
.........
.........
]

Entities:

@Entity
@Table(name = "category")
@Getter @Setter
public class Category {

    @JsonIgnore
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String category1;
    private String category2;
    @OneToMany(mappedBy = "parent", cascade = CascadeType.ALL)
    private List<Subcategory> subcategories;
}

@Entity
@Table(name = "subcategory")
@Getter @Setter
public class Subcategory {

    @JsonIgnore
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    @JsonIgnore
    private int parent;
    private String field1;
    private String field2;
    private String field3;
    private String field4;
}

Controller:

@RestController
public class MyController {

    private final DataService dataService;

    @Autowired
    public MyController(DataService dataService) {
        this.dataService = dataService;
    }

    @GetMapping("/categories")
    public List<Category> getAllCategories() {
        return dataService.getAllCategories();
    }

Repository

public interface MyRepository extends JpaRepository<Category, Long> {
    List<MyRepository> findAll();
}

DataService

@Component
public class DataService {
    private MyRepository myRepository;

    @Autowired
    public DataService(MyRepository myRepository) {
        this.myRepository = myRepository;
    }

    public List<Category> getAllCategories() { return myRepository.findAll(); }

I now want to add a new call to my API, /limitedCategories, which does not return all of the fields. For example, "category2" of the parent entity, and "field4" of the nested entity shall be excluded.

Problem:

I don't manage to manually select the desired fields within my JPA Repository, and also wouldn't know how to deal with the nested object.
The simple idea to just use findAll and exclude those fields using @JsonIgnore is not possible, as my first request still needs those fields.
When using @Query annotation within my repository to fetch only the desired fields, I cannot find a way to fetch the nested fields for my JSON.

Thanks in advance.

I'm using Spring Data JPA 2.2.1 with a Spring Boot Web 2.2.1.

Entities represent what you want to persist in your database tables. Use a different (DTO) class to represent what you want to return as JSON from your endpoint. Transform your entities into instances of this DTO class. — JB Nizet, Nov 18 '19 at 23:42

score 0 · Answer 1 · answered Nov 19 '19 at 01:44

If you are using Jackson API, I recommend you to use @JsonView feature.

For example

class Person {
   // it will be add always
   Integer id;

   // it will be add only for PutFirstName case
   @JsonView(Views.PutFirstName.class)
   String firstName;

   // it will be add only for PutLastName case
   @JsonView(Views.PutLastName.class)
   String lastName;
} 

class Views {
   static class PutFirstName{}
   static class PutLastNastName{}
}

// Controller 
@JsonView(Views.PutFirstName.class)
@GetMapping
Person getFirstName(){
     // result : {id,firstName}
}

@JsonView(Views.PutLastName.class)
@GetMapping
Person getLastName(){
    // result : {id, lastName}
}

Java Spring Data JPA and REST API: exclude fields of nested JSON object

1 Answers1