Posted By: alex
According to the HTTP/1.1 Spec:
POSTmethod is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the
In other words,
POST is used to create.
PUTmethod requests that the enclosed entity be stored under the supplied
Request-URI. If the
Request-URIrefers to an already existing resource, the enclosed entity SHOULD be considered as a modified version of the one residing on the origin server. If the
Request-URIdoes not point to an existing resource, and that URI is capable of being defined as a new resource by the requesting user agent, the origin server can create the resource with that URI.”
PUT is used to create or replace.
So, which one should be used to create a resource? Or one needs to support both?
Both PUT and POST can be used for creating.
You have to ask, "what are you performing the action upon?", to distinguish what you should be using. Let’s assume you’re designing an API for asking questions. If you want to use POST, then you would do that to a list of questions. If you want to use PUT, then you would do that to a particular question.
Great, both can be used, so which one should I use in my RESTful design:
You do not need to support both PUT and POST.
Which you use is up to you. But just remember to use the right one depending on what object you are referencing in the request.
- Do you name the URL objects you create explicitly, or let the server decide? If you name them then use PUT. If you let the server decide then use POST.
- PUT is idempotent, so if you PUT an object twice, it has no effect. This is a nice property, so I would use PUT when possible.
- You can update or create a resource with PUT with the same object URL
- With POST you can have 2 requests coming in at the same time making modifications to a URL, and they may update different parts of the object.
I wrote the following as part of another answer on SO regarding this:
Used to modify and update a resource
POST /questions/<existing_question> HTTP/1.1 Host: www.example.com/
Note that the following is an error:
POST /questions/<new_question> HTTP/1.1 Host: www.example.com/
If the URL is not yet created, you
should not be using POST to create it
while specifying the name. This should
result in a ‘resource not found’ error
<new_question>does not exist
yet. You should PUT the
resource on the server first.
You could though do something like
this to create a resources using POST:
POST /questions HTTP/1.1 Host: www.example.com/
Note that in this case the resource
name is not specified, the new objects
URL path would be returned to you.
Used to create a resource, or
overwrite it. While you specify the
resources new URL.
For a new resource:
PUT /questions/<new_question> HTTP/1.1 Host: www.example.com/
To overwrite an existing resource:
PUT /questions/<existing_question> HTTP/1.1 Host: www.example.com/
Additionally, and a bit more concisely, RFC 7231 Section 4.3.4 PUT states (emphasis added),
The PUT method requests that the state of the target resource be
replacedwith the state defined by the representation
enclosed in the request message payload.