API supporting application/xml and application/hal+json

[muItilingualism]

Hi, I am having trouble getting application/xml and application/hal+json to work together.

I'm using quarkus-hal and quarkus-rest-links for hal+json, xml is just JAXB

I have an endpoint

@GET
@Path("/users")
@Produces({ MediaType.APPLICATION_XML, RestMediaType.APPLICATION_HAL_JSON })
@RestLink(rel = "list")
@InjectRestLinks(RestLinkType.TYPE)
public List<User> all() { //notice the User object is wrapped in a List collection
    return this.userService.all();
}

A User object looks like this

@AllArgsConstructor
@NoArgsConstructor
@XmlRootElement(name = "user")
public class UserResponse {
    @XmlElement
    @RestLinkId
    public Long id;
    
    @XmlElement
    public String username;

    @XmlElement
    public Set<String> role;
}

This does not compile, because JAXB needs the List to be wrapped in a parent class, like the following:

@XmlRootElement(name = "users")
@AllArgsConstructor
@NoArgsConstructor
public class UserResponseList {
    
    @XmlElement(name = "user")
    public List<UserResponse> users;
}

So lets do that and also change the endpoint to look like the following

@GET
@Path("/users")
@Produces({ MediaType.APPLICATION_XML, RestMediaType.APPLICATION_HAL_JSON })
@RestLink(rel = "list")
@InjectRestLinks(RestLinkType.TYPE)
public UserResponseList all() { //notice the new return type UserResponseList
    return this.userService.all();
}

New problems arise.

1. The @RestLink annotation requires classes, even classes which only wrap a collection, to have an ID.
   1a. Hence, the the xml format is now malformed due to the new ID field
   1b. And the hal+json format is malformed both due to the new ID field but also because it now serializes an custom parent class instead of a collection.

Has anyone else ever had this issue? My solution for now is to give up XML as JSON generally is favored.

Any and all suggestions please!