Question

I get confused when and why should you use specific verbs in REST?

I know basic things like:

Get -> for retrieval
Post -> adding new entity
PUT -> updating
Delete -> for deleting

These attributes are to be used as per the operation I wrote above but I don’t understand why?
What will happen if inside Get method in REST I add a new entity or inside POST I update an entity? or may be inside DELETE I add an entity. I know this may be a noob question but I need to understand it. It sounds very confusing to me.

Answer 1

@archil has an excellent explanation of the pitfalls of misusing the verbs, but I would point out that the rules are not quite as rigid as what you’ve described (at least as far as the protocol is concerned).

• GET MUST be safe. That means that a GET request must not change the server state in any substantial way. (The server could do some extra work like logging the request, but will not update any data.)
• PUT and DELETE MUST be idempotent. That means that multiple calls to the same URI will have the same effect as one call. So for example, if you want to change a person’s name from “Jon” to “Jack” and you do it with a PUT request, that’s OK because you could do it one time or 100 times and the person’s name would still have been updated to “Jack”.
• POST makes no guarantees about safety or idempotency. That means you can technically do whatever you want with a POST request. However, you will lose any advantage that clients can take of those assumptions. For example, you could use POST to do a search, which is semantically more of a GET request. There won’t be any problems, but browsers (or proxies or other agents) would never cache the results of that search because it can’t assume that nothing changed as a result of the request. Further, web crawlers would never perform a POST request because it could not assume the operation was safe.

The entire HTML version of the world wide web gets along pretty well without PUT or DELETE and it’s perfectly fine to do deletes or updates with POST, but if you can support PUT and DELETE for updates and deletes (and other idempotent operations) it’s just a little better because agents can assume that the operation is idempotent.

See the official W3C documentation for the real nitty gritty on safety and idempotency.