I am looking to expose some domain RESTful APIs on top of an existing project. One of the entities I need to model has a single document: settings. Settings are created with the application and is a singleton document. I'd like to expose it via a well-designed resource-based RESTful API.
Normally when modeling an API for a resource with many items its something like:
GET /employees/ <-- returns [] of 1-* items
GET /employees/{id}/ <-- returns 1 item
POST /employees/ <-- creates an item
PUT /employees/{id}/ <-- updates all fields on specific item
PATCH /employees/{id}/ <-- updates a subset of fields specified on an item
DELETE /employees/{id}/ <-- deletes a specific item
OPTION 1: If I modeled settings in the same way then the following API is built:
GET /settings/ <-- returns [] of 1-* items
[{ "id": "06e24c15-f7e6-418e-9077-7e86d14981e3", "property": "value" }]
GET /settings/{id}/ <-- returns 1 item
{ "id": "06e24c15-f7e6-418e-9077-7e86d14981e3", "property": "value" }
PUT /settings/{id}/
PATCH /settings/{id}/
This to me has a few nuances:
We return an array when only 1 item CAN and EVER WILL exist. Settings are a singleton that the application creates.
We require knowing the id to make a request only returning 1 item
We require the id of a singleton just to PUT or PATCH it
OPTION 2: My mind then goes in this direction:
GET /settings/ <-- returns 1 item
{ "id": "06e24c15-f7e6-418e-9077-7e86d14981e3", "property": "value" }
PUT /settings/
PATCH /settings/
This design removes the nuances brought up below and doesn't require an id to PUT or PATCH. This feels the most consistent to me as all requests have the same shape.
OPTION 3: Another option is to add the id back to the PUT and the PATCH to require it to make updates, but then an API user must perform a GET just to obtain the id of a singleton:
GET /settings/ <-- returns 1 item
{ "id": "06e24c15-f7e6-418e-9077-7e86d14981e3", "property": "value" }
PUT /settings/{id}/
PATCH /settings/{id}/
This seems inconsistent because the GET 1 doesn't have the same shape as the UPDATE 1 request. It also doesn't require a consumer to perform a GET to find the identifier of the singleton.
Is there a preferred way to model this?
Does anyone have any good reference material on modeling RESTful APIs for singleton resources? I am currently leaning towards OPTION 2 but I'd like to know if there are good resources or standards that I can look into.
Is there a compelling reason to require an API consumer to make a GET for the id of a resource to then use it in an update request, perhaps for security reasons, etc?
The ID of the Resource is the Url itself and not necessarily a Guid or UUID. The Url should uniquely IDentify the Resource, in your case the Settings entity.
But, in order to be RESTfull, you must point to this resource in your index Url (i.e. the / path) with an appropriate rel attribute, so the client will not hardcode the Url, such as this:
GET /
{ ....
"links": [
{ "url" : "/settings", "rel" : "settings" }
], ...
}
There are no specifics to accesing a singleton resource other than the Url will not contain a Guid, Uuid or any other numeric value.
Option 2 is perfectly RESTful, as far as I can tell.
The core idea behind RESTful APIs is that you're manipulating "resources". The word "resource" is intentionally left vague so that it can refer to whatever is important to the specfic application, and so that the API can focus only on how content will be accessed regardless of what content will be accessed.
If your resource is a singleton, it does not make sense to attribute an ID value to it. IDs are very useful and commonly used in RESTful APIs, but they are not a core part of what makes an API RESTful, and, as you have noticed, would actually make accessing singleton resources more cumbersome.
Therefore, you should just do away with IDs and have both
GET /settings/
and
GET /settings/{id}
always return the settings singleton object. (access-by-id is not required, but it's nice to have just in case someone tries it). Also, be sure to document your API endpoint so consumers don't expect an array :)
Re: your questions,
I believe option 2 would be the preferred way of modeling this, and I believe requiring your consumer to make a GET for the id would actually be somewhat of an anti-pattern.
I think the confusion here is because the word settings is plural, but the resource is a singleton.
Why not rename the resource to /configuration and go with option 2?
It would probably be less surprising to consumers of your API.
You're probably overthinking it. There's no concept of singleton in HTTP or REST.
GET /settings/ is perfectly fine.
By the way, we can hardly relate this to DDD - at least not if you don't give more context about what settings means in your domain.
It might also be that you're trying to tack an "Entity with ID" approach on Settings when it's not appropriate. Not all objects in a system are entities.
Lets say I have the following classes:
company
user
address
a company object can contain users and addresses,
a user object contains addresses
company can exist on its own, but users and address is always a part of company or user (a composition in UML wording):
company ->
addresses
users ->
addresses
Now I want use the right REST-structure for POST (insert) and PUT (update) requests. What would be the correct approach?
variant 1:
// insert address:
POST /api/company/{companyId}/addresses
POST /api/company/{companyId}/users/{userId}/addresses
// update address:
PUT /api/company/{companyId}/addresses/{addressId}
PUT /api/company/{companyId}/users/{userId}/addresses/{addressId}
variant 2:
// insert address:
POST /api/address // companyId, userId etc. as parameter
// update address:
PUT /api/address/{addressId}
My personal gut feeling would be to use variant 1 for creation (POST) and variant 2 for updates (PUT), because variant 1 seems "cleaner" for creation but for update variant 2 would be better because it does not require a parentId (company or user)
First, REST is an architectur style not a protocol. This means that there is no right or wrong in how you define your URI. The only requirement Roy Fielding put in place was that each resource has to have a unique resource identifier (URI). The operation you may do on those URIs (verbs) are defined by the underlying hypertext transfer protocol (HTTP).
Second, there are certain best practices like using a sub-resource for resources that are embedded in other resources (especially if they can't exist without the parent resource) as in your case with addresses and users/companies
As you have certain issues with updating a sub-resource:
Usually to update a resource HTTP verb PUT is used which has the limitation of replacing the current state (all the available data) with the state you've sent to the server (in case the update goes well). As there is no partial update yet defined in HTTP some use the PUT verb a bit fuzzy and only update what is available within the request, though issuing a PATCH request and only updating these fields is probably more correct in terms of HTTP specification.
Sub-resources are very similar to regular resources. If you update a sub-resource you don't need to update the parent resource. In your particular case, if you want to update a user's address but not the user itself, you issue a PUT /users/{userId}/addresses/{addressId} HTTP/1.1 request containing the new state of the address to the server. The request body may look like this:
{
"street": "Sample Street 1"
"city": "Sampletown",
"zip": "12345",
"country": "Neverland",
"_links": {
"self": { "href": "/users/{userId}/addresses/{addressId} }
"googleMap": { "href": "https://www.google.com/maps/place/Liberty+Island/#40.6883129,-74.042817,16.4z/data=!4m2!3m1!1s0x0000000000000000:0x005f3b2fa5c0821d" }
}
}
If you want to follow the HTTP PUT verb closely and have dynamic fields, which may appear during runtime, you might have to alter the current table definition eventually, delete the old address entry and insert a new entry with the provided information (depending on the DB layer you are using SQL vs NoSQL). Note the HTTP PUT verb semantic!
On utilizing a fuzzy update strategy (=partial update) a simple update statement should be fine. Here you can simply ignore the additional userId contained within the URI, though this is not (yet) fully HTTP compliant - at least in regards to the spec. In that particular case it is your choice which version of URI you choose, though version 2 only works in the latter case while version 1 works in both cases.
Lets say I have a rest service that allows applications to create User object
URI: /users
HTTP Method:POST
{
"firstName":"Edward",
"lastName": "Nygma",
"dob": "01011981",
"email": "en#gc.com",
"phone": "0123456789"
}
On the first POST the User object is created and and the User ID is returned
Lets say there is a second service that allows the user to update the lastName and email fields.
URI: /user/1/last-email
HTTP Method: POST
{
"lastName": "scissorhands",
"email": "ec#bc.com"
}
Let's say for the sake of bandwidth sending the full User object is not an option for this update call.
Is this the correct way to do a partial update that involves several fields? Also using PATCH is out of the question.
Edit:
I know that the correct way to do this restfully would be to post an update to each field as a sub resource but lets say for the sake of bandwidth/business requirements that this update has to be done in a single call. Is this the correct way to do so?
Edit 2:
Our implementation does not support the HTTP PATCH method, hence why I indicated in the initial question that using patch is out of the question. That being said, maybe I should rephrase the question.
Since system/business requirements prevent us from implementing this correctly in a RESTful manor. What is the best way to handle this scenario.
Putting the verb "update-" suddenly makes it feel like it's an RPC call. What do you do when you want to delete this email? Doing a DELETE action on this URI looks a bit silly.
URI: /user/1/email and
URI: user/1/lastname would make more sense as EMAIL would just be a subresource and you can use all the verbs on those resources.
Yes, this would take 2 calls in case you want to update 2 resources instead of 1.
For partial updates of a resource use "PATCH" verb on the resource. This way you would not need a new URI at all. (Best practice for partial updates in a RESTful service)
Reference: http://restcookbook.com/HTTP%20Methods/patch/
Quote:
When should we use the PATCH HTTP method?
The HTTP methods PATCH can be used to update partial resources. For instance, when you only need to update one field of the resource, PUTting a complete resource representation might be cumbersome and utilizes more bandwidth
See more at: http://restcookbook.com/HTTP%20Methods/patch/#sthash.jEWLklrg.dpuf
Let's say I want to have a RESTful resource for people, where the client is able to assign ID.
A person looks like this: {"id": <UUID>, "name": "Jimmy"}
Now, how should the client save (or "PUT") it?
PUT /person/UUID {"id": <UUID>, "name": "Jimmy"} - now we have this nasty duplication that we have to verify all the time: Does the ID in body match the one in path?
Asymmetric representation:
PUT /person/UUID {"name": "Jimmy"}
GET /person/UUID returns {"id": <UUID>, "name": "Jimmy"}
No IDs in body - ID only in location:
PUT /person/UUID {"name": "Jimmy"}
GET /person/UUID returns {"name": "Jimmy"}
No kind of POST seems like a good idea since the ID is generated by the client.
What are the common patterns and ways to solve it? IDs only in location seems like the most dogmatically correct way, but it also makes the practical implementation harder.
There is nothing wrong in having different read/write models: the client can write one resource representation where after the server can return another representation with added/calculated elements in it (or even a completely different representation - there is nothing in any spec against that, the only requirement is that PUT should create or replace the resource).
So I would go for the asymmetric solution in (2) and avoid the "nasty duplication check" on the server side when writing:
PUT /person/UUID {"name": "Jimmy"}
GET /person/UUID returns {"id": <UUID>, "name": "Jimmy"}
If it is a public API you should be conservative when you reply, but accept liberally.
By that I mean, you should support both 1 and 2. I agree that 3 doesn't make sense.
The way to support both 1 and 2 is to get the id from the url if none is supplied in the request body, and if it is in the request body, then validate that it matches the id in the url. If the two do not match, then return a 400 Bad Request response.
When returning a person resource be conservative and always include the id in the json, even though it is optional in the put.
Just FYI, the answers here are wrong.
TLDR; If you're using PUT, you should have the id in the body. If you are using PATCH, you do not need the id in the body.
See:
https://restfulapi.net/rest-api-design-tutorial-with-example/
https://restfulapi.net/rest-put-vs-post/
https://restfulapi.net/http-methods/#patch
PUT
Use PUT APIs primarily to update existing resource (if the
resource does not exist, then API may decide to create a new resource
or not). If a new resource has been created by the PUT API, the origin
server MUST inform the user agent via the HTTP response code 201
(Created) response and if an existing resource is modified, either the
200 (OK) or 204 (No Content) response codes SHOULD be sent to indicate
successful completion of the request.
If the request passes through a cache and the Request-URI identifies
one or more currently cached entities, those entries SHOULD be treated
as stale. Responses to this method are not cacheable.
Use PUT when you want to modify a singular resource which is already a
part of resources collection. PUT replaces the resource in its
entirety. Use PATCH if request updates part of the resource.
PATCH
HTTP PATCH requests are to make partial update on a resource. If you
see PUT requests also modify a resource entity so to make more clear –
PATCH method is the correct choice for partially updating an existing
resource and PUT should only be used if you’re replacing a resource in
its entirety.
So you should use it in this way:
POST /device-management/devices : Create a new device
PUT /device-management/devices/{id} : Update the device information identified by "id"
PATCH /device-management/devices/{id} : Partial-update the device information identified by "id"
RESTful practices indicate that it shouldn't matter what you PUT at /{id}--the content of the record should be updated to the one provided by the payload--but GET /{id} should still link to the same resource.
In other words, PUT /3 may update to payload id to 4, but GET /3 should still link to the same payload (and return the one with id set to 4).
If you are deciding that your API requires the same identifier in the URI and the payload, it's your job to make sure it matches, but definitely use PATCH instead of PUT if you are excluding the id in the payload that should be there in its entirety. This is where the accepted answer got it wrong. PUT must replace the entire resource, where-as patch may be partial.
One solution to this issue involves the somewhat confusing concept of "Hypertext As The Engine Of Application State," or "HATEOAS." This means that a REST response contains the available resources or actions to be performed as hyperlinks. Using this method, which was part of the original conception of REST, the unique identifiers/IDs of resources are themselves hyperlinks. So, for example, you could have something like:
GET /person/<UUID> {"person": {"location": "/person/<UUID>", "data": { "name": "Jimmy"}}}
Then, if you want to update that resource, you could do (pseudocode):
updatedPerson = person.data
updatedPerson.name = "Timmy"
PUT(URI: response.resource, data: updatedPerson)
One advantage of this is that the client doesn't have to have any idea about the server's internal representation of User IDs. The IDs could change, and even the URLs themselves could change, as long as the client has a way to discover them. For example, when getting a collection of people, you could return a response like this:
GET /people
{ "people": [
"/person/1",
"/person/2"
]
}
(You could, of course, also return the full person object for each person, depending on the needs of the application).
With this method, you think of your objects more in terms of resources and locations, and less in terms of ID. The internal representation of unique identifier is thus decoupled from your client logic. This was the original impetus behind REST: to create client-server architectures that are more loosely coupled than the RPC systems that existed before, by using the features of HTTP. For more information on HATEOAS, look at the Wikipedia article as well as this short article.
In an insert you do not need to add the id in the URL. This way if you send an ID in a PUT you may interpreted as an UPDATE to change the primary key.
INSERT:
PUT /persons/
{"id": 1, "name": "Jimmy"}
HTTP/1.1 201 Created
{"id": 1, "name": "Jimmy", "other_field"="filled_by_server"}
GET /persons/1
HTTP/1.1 200 OK
{"id": 1, "name": "Jimmy", "other_field"="filled_by_server"}
UPDATE
PUT /persons/1
{"id": "2", "name": "Jimmy Jr"} -
HTTP/1.1 200 OK
{"id": "2", "name": "Jimmy Jr", "other_field"="filled_by_server"}
GET /persons/2
HTTP/1.1 200 OK
{"id": "2", "name": "Jimmy Jr", "other_field"="updated_by_server"}
The JSON API uses this standard and solves some issues returning the inserted or updated object with a link to the new object. Some updates or inserts may include some business logic that will change additional fields
You will also see that you can avoid the get after the insert and update.
While it's Ok to have different representations for different operations, a general recommendation for PUT is to contain the WHOLE payload. That means that id should be there as well. Otherwise, you should use PATCH.
Having said that, I think PUT should mostly be utilised for updates and the id should always be passed in the URL as well. As a result of that, using PUT to update the resource identifier is a bad idea.
It leaves us in an undesirable situation when id in the URL can be different from the id in the body.
So, how do we resolve such a conflict? We basically have 2 options:
throw a 4XX exception
add a Warning(X-API-Warn etc) header.
That's as close as I can get to answering this question because the topic in general is a matter of opinion.
This has been asked before - the discussion is worth a look:
Should a RESTful GET response return a resource's ID?
This is one of those questions where it's easy to get bogged down into debate around what is and is not "RESTful".
For what it's worth, I try to think in terms of consistent resources and not change the design of them between methods. However, IMHO the most important thing from a usability perspective is that you are consistent across the entire API!
There is nothing bad in using different approaches. but i think the best way is the solution with 2nd.
PUT /person/UUID {"name": "Jimmy"}
GET /person/UUID returns {"id": <UUID>, "name": "Jimmy"}
it is mostly used in this way even the entity framework use this technique when the entity is added in dbContext the class without the generated ID is ID generated by reference in Entity Framework.
You may need to look into PATCH/PUT request types.
PATCH requests are used to update a resource partially whereas in PUT requests, you have to send the entire resource where it gets overridden on the server.
As far as having an ID in the url is concerned, I think you should always have it as it is a standard practice to identify a resource. Even the Stripe API works that way.
You can use a PATCH request to update a resource on the server with ID to identify it but do not update the actual ID.
I'm looking at this from a JSON-LD/ Semantic Web point of view because that's a good way to go to achieve real REST conformance as I have outlined in these slides. Looking at it from that perspective, there is no question to go for option (1.) as the ID (IRI) of a Web resource should always be equal to the URL which I can use to look-up/ dereference the resource.
I think the verification is not really hard to implement nor is it computationally intens; so I don't consider this a valid reason for going with option (2.).
I think option (3.) is not really an option as POST (create new) has a different semantics than PUT (update/ replace).
I am defining a REST API, one of the end points would match a resource (not exactly like that, but analogous) that holds a M-N relationship, for instance, let's says permissions by user, so a user could have read/write....
I was thinking of mapping to get it like:
/permissions/{user}
That would represent what I am interested in representing, but that would bring back an array of permissions rather than just one object, in an Id request. Is that something that would be RESTFUL? How would it be represented otherwise?
My doubts came when trying to use Restangular to consume this resource and having to fiddle around to make it work (as it was expecting an object rather than an array). It could also be a problem related to my limited knowledge of Restangular, of course.
Thanks,
You could return a JSON list of permissions for that user;
{ "permissions": { "read": "true", "write": "false" }