spring hateoas generates different responses for collection or pojo - spring

Question

I have two classes
import org.springframework.hateoas.ResourceSupport;
public class A{}
public class B{}
public class AResource extends ResourceSupport {
private final A a;
}
public class BResource extends ResourceSupport {
private final B b;
}
#Controller
public class Controller {
#RequestMapping
#ResponseBody
public Set<AResource> giveMeColl() {
}
#RequestMapping
#ResponseBody
public BResource giveMeSingle() {
}
}
both responses add links object but for resource A is "links" and for resource B is "_link" and also structure changes
//RESPONSE FOR A
[
{
"content":{
//my fancy object
},
"links":[
{
"rel": "self",
"href": "http://localhost:8080/myid/22"
}
]
}
]
{
"content":{
//my fancy object
},
"_links":[
{
"self": "http://localhost:8080/myid/22/someelse/33"
}]
}
both resources are constructed with assemblers and both are adding the link from the ids
AResource aresource = new AResource(a);
resource.add(linkTo(methodOn(Controller.class).giveMeColl()).withSelfRel());
BResource bresource = new BResource(b);
resource.add(linkTo(methodOn(Controller.class).giveMeSingle()).withSelfRel());
Response headers for a is
"content-type": "application/json;charset=UTF-8"
and for b
"content-type": "application/hal+json;charset=UTF-8"
Could it be because returning an array is not really Restful? as Some post suggest
p.s. I have added and removed #EnableHypermediaSupport but doesn't seem to affect the problem.

Answer 1

"_links" follows the HAL specification. Spring HATEOAS includes a dedicated serializer for that, but it is only used for classes that extend ResourceSupport.
Returning a simple array is not exactly "unRESTful", but it doesn't meet the REST maturity level 3 (Hypermedia controls). In order to achieve that you can wrap the collection into a Resources instance, which extends ResourceSupport. You should get the same link serialization for both types then.