Map<> Entity association stay empty when POST on parent entity [DATAREST-960]

Benjamin Legendre opened DATAREST-960 and commented

Here a simple use case :

@Entity
@Table(name="orders")
public class Order {

    @Id
    @GeneratedValue
    private Integer id;

    private String name;

    @ManyToMany
    @JoinTable(name = "line_items",
            joinColumns = { @JoinColumn(name="order_id") },
            inverseJoinColumns = { @JoinColumn(name="product_id") })
    @MapKeyColumn(name="line_number")
    private Map<Integer, Product> lineItems;

@Entity
@Table(name="products")
public class Product {

    @Id
    @GeneratedValue
    private Integer id;
    
    private String name;

}

Doing POST http://localhost/orders :

{
      "name" : "order-2",
      "lineItems" : {
        "1" : "http://localhost:15571/products/1",
        "2" : "http://localhost:15571/products/2",
        "3" : "http://localhost:15571/products/3"
      }
}

returns:

HTTP/1.1 201 
Location: http://localhost:15571/orders/2
Content-Type: application/hal+json;charset=UTF-8
Transfer-Encoding: chunked
Date: Tue, 13 Dec 2016 17:26:23 GMT

{
  "name" : "order-2",
  "_links" : {
    "self" : {
      "href" : "http://localhost:15571/orders/2"
    },
    "order" : {
      "href" : "http://localhost:15571/orders/2"
    },
    "lineItems" : {
      "href" : "http://localhost:15571/orders/2/lineItems"
    }
  }
}
}

Unfortunately the lineItems remains empty:
POST http://localhost:15571/orders/2/lineItems

HTTP/1.1 200 
Content-Type: application/hal+json;charset=UTF-8
Transfer-Encoding: chunked
Date: Tue, 13 Dec 2016 17:29:52 GMT

{
  "content" : { }
}

I don't know if it is a bug or something not implemented. Passing uris this way works well on others types of collections (Set<Entity>, List<Entity> etc.).

More generally i have not found any relevant way to alter the state of a Map association:
PATCH/PUT on the association resource results in what is described on DATAREST-308. In fact it is not possible to specify the "key" of Map using Content-Type: text/uri-list by design.

A small project is attached with Entities of the use case

Affects: 2.5.5 (Hopper SR5)

Attachments:

• sdr-map-bug-example.zip (7.19 kB)