Hibernate, Saving new entity without fetching associated entities

Question

I'm using spring boot and hibernate, trying to save an entity with a @ManyToOne relation by posting only the id of the referenced entity

@Entity
@Table(name = "foo_table")
public class Foo implements Serializable {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private id;

    @NotNull
    @JsonIdentityReference(alwaysAsId=true)
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name = "bar_id", nullable = false)
    private Bar bar;

    ...
}


@Entity
@Table(name = "bar_table")
public class Bar implements Serializable {
    @Id @GeneratedValue(strategy = GenerationType.IDENTITY)
    private id;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "bar")
    private Set<Foo> foos;

    ...
}

And the controller code is similar to:

@RestController
public class FooController {

    @Autowired
    private FooRepo fooRepo;

    @RequestMapping(value = "/foo", method= RequestMethod.POST)
    public Foo foo(@RequestBody @Valid Foo foo)
        throws Exception {
        return fooRepo.save(foo);
    }
}

And the posted JSON is similar to

{
    "bar" : 1
}

However I'm getting an error in jackson while deserializing

"Could not read document: Unresolved forward references for: Object id [1]"

Artem Novikov · Accepted Answer · 2016-08-19 22:52:51Z

2

You either change your json so that you provide an object type for bar field where Jackson expects it, instead of an integer, and pass id explicitly:

{
    "bar": {
        "id": 1
    }
}

OR

Create the corresponding setter inside your Foo class - a setter that has the same input type as the ID type - in your case an integer:

public class Foo implements Serializable {
    ...

    @JsonProperty("bar")
    public void setBar(int id) {
        // For example:
        this.bar = new Bar(id);
    }
}

edited Aug 19, 2016 at 22:52

answered Aug 19, 2016 at 21:40

Artem Novikov

4,7071 gold badge30 silver badges37 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Badr Ghatasheh Over a year ago

While this works (after adding @JsonProperty(access = Access.WRITE_ONLY)), however, I'm trying to achieve serializing and deserializing Bar in the same manner using @JsonIdentityReference(alwaysAsId=true)

Badr Ghatasheh Over a year ago

i.e. if it's represented in response as { bar : 1 }, I need to send it in post as {bar : 1} too.

Artem Novikov Over a year ago

@BadrGhatasheh I'm sorry, I didn't get it from the question - the provided classes don't have those annotations that you say you use. Updated my answer.

Badr Ghatasheh Over a year ago

But that doesn't work since "new Bar()" isn't attached to the entity manager and will fail to insert

Artem Novikov Over a year ago

@BadrGhatasheh yes, that question rather refers to deserialization error. But it's up to you how to handle the integrity of data. You could load your entity from DB by calling dao.getBarById(id) after which you would have a managed instance. Actually, it's not a good idea to mess with transactions during serializaton/deserialization steps - usually you create additional classes FooDto and BarDto that are used for web layer only and then convert them to your entities manually inside the controller, ensuring all the fields the way you need - which fields to load, which to ignore.

Collectives™ on Stack Overflow

Hibernate, Saving new entity without fetching associated entities

1 Answer 1

OR

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

OR

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related