CODEWITHSUNDEEP
web-servicesrestrestful-architecture
Mladen B.
Mladen B.

Reputation: 3013

Non-idempotent but safe transition in the REST architecture

Can you please provide an example of a RESTful API call (using HTTP protocol) which is non-idempotent and safe, at the same time (does something like that even exist)?

To elaborate a little bit on this, while reading about the Hypermedia-Oriented Design, I've encountered the 4 affordance aspects that describe each transition: safety, idempotence, mutability and transclusion. Also, I've encountered a table which describes the HTTP verbs through those aspects and it goes like this:

---------------------------------
HTTP Method    Idempotent    Safe
---------------------------------
OPTIONS        yes           yes
GET            yes           yes
HEAD           yes           yes
PUT            yes           no
POST           no            no
DELETE         yes           no
PATCH          no            no
---------------------------------

My intuition tells me that all of the safe methods are automatically idempotent too (but not vice versa). I would just like to either confirm or refute this once and for all.

Thanks in advance for the answers.

Upvotes: 1

Views: 97

Answers (2)

Jonathan W
Jonathan W

Reputation: 3799

Yes. All safe methods are also idempotent, but they refer to two different (but related) qualities of a RESTful API.

A safe method call (one which does not modify the state of the resource on the server) may be issued multiple times by the client without affecting the state of the server (the definition of idempotency).

Upvotes: 1

Aaron Brager
Aaron Brager

Reputation: 66292

A safe method - one that does not modify anything - is by definition idempotent. Since it has not changed anything, it will have the same effect (that is, no effect whatsoever) no matter how many times you call it.

Upvotes: 1

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