People have been talking about including hypermedia with REST Resources, but
there are very few public examples that implement all of it. One common
technique is to add *_url
attributes:
{ "id": 1
, "self_url": "/issues/1"
, "comments_url": "/issues/1/comments"
}
This only gives you room to put a URL. Because of this, I've been leaning towards HAL:
{ "id": 1
, "_links":
{ "self": {"href": "/issues/1"}
, "comments": {"href": "/issues/1/comments"}
, "close": {"href": "/issues/1/close", "method": "post"}
}
}
Should hypermedia tell you when you have permissions to access those resources?
// admin permissions
{ "id": 1
, "_links":
{ "self": {"href": "/issues/1", "method": "get,patch,delete"}
, "close": {"href": "/issues/1/close", "method": "post"}
}
}
// read-only permissions, no access to close/update issues
{ "id": 1
, "_links":
{ "self": {"href": "/issues/1", "method": "get"}
}
}
The HAL spec doesn't mention method
properties at all. But, I think letting
a client know the difference between an Issue I can edit or close is very
useful. Is it any better if I have a separate relation for each action?
{ "id": 1
, "_links":
{ "self": {"href": "/issues/1", "method": "get"}
"edit": {"href": "/issues/1", "method": "patch" }
"delete": {"href": "/issues/1", "method": "delete" }
, "close": {"href": "/issues/1/close", "method": "post"}
}
}
Finally, is the "close" relation even appropriate? Or should I assume clients know they can close Issues by setting "state" to "closed" (which is how the GitHub Issues API works)?
@aaronjensen @steveklabnik
Requiring a "forms-like" JSON-based representation was one of the motivations for creating
actions
in the Siren hypermedia type. See an example here: https://github.com/kevinswiber/siren#exampleHAL aims to put more information in the link relation documentation. Siren includes some of this inline, as to accomodate change. For instance, the method used or input field types could change on the fly. A client may need to be aware of an action by name and any input fields ahead of time, but that's not a requirement.
I find it helpful to break up hypermedia design into two parts: format and interaction. The media type defines the format. Additional documentation can provide the interaction hints: link relations, action names, input field names, etc. Atom has done this successfully.