Java Spring @RequestBody-如何通过两个连接的实体接收有效的JSON

Question

I've got simple

DB SCHEMA

Contact
-------
int: id
varchar: name

Note
-------
int: id
int: id_contact
varchar: title

As you can see, tables are connected. My goal is to add note by AJAX request with id_contact provided.

FORM should look like that

<form action="add-note" id="add-note">
    <input type="hidden" name="id_contact" value="20" /> <!-- just a dummy value which corresponds with contact record in DB -->

    note: 
    <input type="text" name="title" class="title">

    <input type="submit" />
</form>

Method to process AJAX request

@RequestMapping(value = "/add-note", method = RequestMethod.POST)
public ResponseEntity<Note> addNote(@RequestBody Note note) {

    // do something with note...

    return new ResponseEntity<Note>(note, HttpStatus.OK);
}

If I don't try to provide id_contact, method addNote works fine, but I'm not able to make spring to convert JSON to Note with Contact in it.

Does anyone know how to achieve it? Thanks in advance

---

EDIT: After all, I ended up with passing id_contact as GET param and handling it like that:

    @RequestMapping(value = "/addNote", method = RequestMethod.POST)
    public ResponseEntity<Note> addNote(@RequestBody Note note, @RequestParam(value = "id_contact") long id_contact) {

            note.setContact(contact_service.findOne(id_contact));
            note_service.insert(note);

            return new ResponseEntity<Note>(note, HttpStatus.OK);
   }

Feel free to answer to my question above - I consider this snippet as a little workaround. (But maybe it's the right way how you would do it by urself?)

---

EDIT2:

Note.java

// imports ommited    
@Entity
    public class Note {

        @Id
        @JsonProperty("url")
        @GeneratedValue(strategy=GenerationType.IDENTITY)
        private long id;

        @ManyToOne
        @JoinColumn(name="id_contact")
        private Contact contact;

        private String title;
// setters/getters ommited

Error I get when trying to send JSON is "400 bad request".

Answer 1

Not sure if this is going to work but try to use dot operator.

<input type="hidden" name="contact.id" value="20" />
<input type="hidden" name="contact.name" value="20" />

RequestBody will try to map the notes Entity, and using nested objects sometimes works.

If not considering creating a json request instead of use the multpart form format.

Answer 2

Neither of your examples from your comments is valid JSON. I believe {"title": "test", "contact" : {"id" : 20}} would work for you in a sense that it will be parsed by Spring properly into a Note . However your form won't produce any JSON, and I can't see any AJAX calls anywhere in your post.