[FIXED] How to properly handle request body with mutual oject references in REST Spring?

Issue

I have entities that have references to themselves, for example:

• Client has many Properties
• Property has many Clients

Returning list of Properties by Client id causes StackOverflowError because it keeps nesting Properties inside Client and so on.

How can I deal with nesting in the most proper / elegant way?

Service

    public Set<Home> getHouses(Long userId) {
        return Utils.iterableToCollection(((HomeRepository) (getRepository())).findAll(), HashSet::new);
    }

Controller

    @GetMapping("/all")
    @ResponseBody
    public GenericResponse getHouses(@RequestParam("id") Long userId) {
        Set<Home> houses = homeService.getHouses(userId);
        return new GenericResponse(
                "houses fetched successfully",
                houses,
                HttpStatus.OK
        );
    }

Home

public class Home extends AbstractEntity<Long> {

    @OneToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "homeAddress_id")
    private Address address;

    @ManyToMany(mappedBy = "properties", fetch = FetchType.EAGER)
    private Set<Client> clients = new HashSet<>();

    @Lob
    private byte[] apartmentPicture;
}

Client

public class Client extends User {

    @ManyToMany(fetch = FetchType.EAGER)
    @JoinTable(name = "CLIENT_HOME",
            joinColumns = @JoinColumn(name = "client_id"),
            inverseJoinColumns = @JoinColumn(name = "home_id")
    )
    private Set<Home> properties = new HashSet<>();
}

Solution

If you use Jackson 2.6+, you can use @JsonProperty(access = Access.WRITE_ONLY) on the property you don't want to serialize. So if you want to include the clients when you fetch your houses, put it on the properties field in your Client class, which will simply ignore that field during serialization. However, I would advise you to decouple your database layer from your representation layer and map every entity to a DTO, that helps you a lot in the long run.

You can read more about the JsonProperty annotation here.

Answered By - Krisz
Answer Checked By - Candace Johnson (JavaFixing Volunteer)