Let's assume there are two resources Binder
and Doc
with association relationship meaning that the Doc
and Binder
stand on their own. Doc
might or might not belong to Binder
and Binder
might be empty.
If I want to design a REST API that allows a user to send a collection of Doc
s, IN A SINGLE REQUEST, like the following:
{
"docs": [
{"doc_number": 1, "binder": 1},
{"doc_number": 5, "binder": 8},
{"doc_number": 6, "binder": 3}
]
}
And for each doc in the docs
,
doc
exists then assign it to Binder
doc
doesn't exist, create it and then assign itI'm really confused as to how this should be implemented:
/binders/docs
?I think that you could use a POST or PATCH method to handle this since they typically design for this.
Using a POST
method is typically used to add an element when used on list resource but you can also support several actions for this method. See this answer: Update an entire resource collection in a REST way. You can also support different representation formats for the input (if they correspond to an array or a single elements).
In the case, it's not necessary to define your format to describe the update.
Using a PATCH
method is also suitable since corresponding requests correspond to a partial update. According to RFC5789 (https://www.rfc-editor.org/rfc/rfc5789):
Several applications extending the Hypertext Transfer Protocol (HTTP) require a feature to do partial resource modification. The existing HTTP PUT method only allows a complete replacement of a document. This proposal adds a new HTTP method, PATCH, to modify an existing HTTP resource.
In the case, you have to define your format to describe the partial update.
I think that in this case, POST
and PATCH
are quite similar since you don't really need to describe the operation to do for each element. I would say that it depends on the format of the representation to send.
The case of PUT
is a bit less clear. In fact, when using a method PUT
, you should provide the whole list. As a matter of fact, the provided representation in the request will be in replacement of the list resource one.
You can have two options regarding the resource paths.
In this case, you need to explicitely provide the link of docs with a binder in the representation you provide in the request.
Here is a sample route for this /docs
.
The content of such approach could be for method POST
:
[
{ "doc_number": 1, "binder": 4, (other fields in the case of creation) },
{ "doc_number": 2, "binder": 4, (other fields in the case of creation) },
{ "doc_number": 3, "binder": 5, (other fields in the case of creation) },
(...)
]
In addition you could also consider to leverage sub routes to describe the link between docs and binders. The hints regarding the association between a doc and a binder doesn't have now to be specified within the request content.
Here is a sample route for this /binder/{binderId}/docs
. In this case, sending a list of docs with a method POST
or PATCH
will attach docs to the binder with identifier binderId
after having created the doc if it doesn't exist.
The content of such approach could be for method POST
:
[
{ "doc_number": 1, (other fields in the case of creation) },
{ "doc_number": 2, (other fields in the case of creation) },
{ "doc_number": 3, (other fields in the case of creation) },
(...)
]
Regarding the response, it's up to you to define the level of response and the errors to return. I see two levels: the status level (global level) and the payload level (thinner level). It's also up to you to define if all the inserts / updates corresponding to your request must be atomic or not.
In this case, you can leverage the HTTP status. If everything goes well, you get a status 200
. If not, another status like 400
if the provided data aren't correct (for example binder id not valid) or something else.
In this case, a status 200
will be returned and it's up to the response representation to describe what was done and where errors eventually occur. ElasticSearch has an endpoint in its REST API for bulk update. This could give you some ideas at this level: http://www.elasticsearch.org/guide/en/elasticsearch/guide/current/bulk.html.
You can also implement an asynchronous processing to handle the provided data. In this case, the HTTP status returns will be 202
. The client needs to pull an additional resource to see what happens.
Before finishing, I also would want to notice that the OData specification addresses the issue regarding relations between entities with the feature named navigation links. Perhaps could you have a look at this ;-)
The following link can also help you: https://templth.wordpress.com/2014/12/15/designing-a-web-api/.
Hope it helps you, Thierry
You probably will need to use POST or PATCH, because it is unlikely that a single request that updates and creates multiple resources will be idempotent.
Doing PATCH /docs
is definitely a valid option. You might find using the standard patch formats tricky for your particular scenario. Not sure about this.
You could use 200. You could also use 207 - Multi Status
This can be done in a RESTful way. The key, in my opinion, is to have some resource that is designed to accept a set of documents to update/create.
If you use the PATCH method I would think your operation should be atomic. i.e. I wouldn't use the 207 status code and then report successes and failures in the response body. If you use the POST operation then the 207 approach is viable. You will have to design your own response body for communicating which operations succeeded and which failed. I'm not aware of a standardized one.
PUT ing
PUT /binders/{id}/docs
Create or update, and relate a single document to a binder
e.g.:
PUT /binders/1/docs HTTP/1.1
{
"docNumber" : 1
}
PATCH ing
PATCH /docs
Create docs if they do not exist and relate them to binders
e.g.:
PATCH /docs HTTP/1.1
[
{ "op" : "add", "path" : "/binder/1/docs", "value" : { "doc_number" : 1 } },
{ "op" : "add", "path" : "/binder/8/docs", "value" : { "doc_number" : 8 } },
{ "op" : "add", "path" : "/binder/3/docs", "value" : { "doc_number" : 6 } }
]
I'll include additional insights later, but in the meantime if you want to, have a look at RFC 5789, RFC 6902 and William Durand's Please. Don't Patch Like an Idiot blog entry.
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