What is the usefulness of PUT and DELETE HTTP request methods?

Question

I've never used PUT or DELETE HTTP Request methods. My tendency is to use GET when the state of the system (my application or website) may not be affected (like a product listing) and to use POST when it is affected (like placing an order). Aren't those two always sufficient, or am I missing something?

Answer 1

DELETE is for deleting the request resource:

The DELETE method requests that the origin server delete the resource identified by the Request-URI. This method MAY be overridden by human intervention (or other means) on the origin server. The client cannot be guaranteed that the operation has been carried out, even if the status code returned from the origin server indicates that the action has been completed successfully …

PUT is for putting or updating a resource on the server:

The PUT method requests that the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers 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-URI does 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 …

For the full specification visit:

• http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html

Since current browsers unfortunately do not support any other verbs than POST and GET in HTML forms, you usually cannot utilize HTTP to it's full extent with them (you can still hijack their submission via JavaScript though). The absence of support for these methods in HTML forms led to URIs containing verbs, like for instance

POST http://example.com/order/1/delete 

or even worse

POST http://example.com/deleteOrder/id/1 

effectively tunneling CRUD semantics over HTTP. But verbs were never meant to be part of the URI. Instead HTTP already provides the mechanism and semantics to CRUD a Resource (e.g. an order) through the HTTP methods. HTTP is a protocol and not just some data tunneling service.

So to delete a Resource on the webserver, you'd call

DELETE http://example.com/order/1 

and to update it you'd call

PUT http://example.com/order/1 

and provide the updated Resource Representation in the PUT body for the webserver to apply then.

So, if you are building some sort of client for a REST API, you will likely make it send PUT and DELETE requests. This could be a client built inside a browser, e.g. sending requests via JavaScript or it could be some tool running on a server, etc.

For some more details visit:

• http://martinfowler.com/articles/richardsonMaturityModel.html
• Are the PUT, DELETE, HEAD, etc methods available in most web browsers?
• Why are there no PUT and DELETE methods in HTML forms
• Should PUT and DELETE be used in forms?
• http://amundsen.com/examples/put-delete-forms/
• http://www.quora.com/HTTP/Why-are-PUT-and-DELETE-no-longer-supported-in-HTML5-forms

Answer 2

Using HTTP Request verb such as GET, POST, DELETE, PUT etc... enables you to build RESTful web applications. Read about it here: http://en.wikipedia.org/wiki/Representational_state_transfer

The easiest way to see benefits from this is to look at this example. Every MVC framework has a Router/Dispatcher that maps URL-s to actionControllers. So URL like this: /blog/article/1 would invoke blogController::articleAction($id); Now this Router is only aware of the URL or /blog/article/1/

But if that Router would be aware of whole HTTP Request object instead of just URL, he could have access HTTP Request verb (GET, POST, PUT, DELETE...), and many other useful stuff about current HTTP Request.

That would enable you to configure application so it can accept the same URL and map it to different actionControllers depending on the HTTP Request verb.

For example:

if you want to retrive article 1 you can do this:

GET /blog/article/1 HTTP/1.1 

but if you want to delete article 1 you will do this:

DELETE /blog/article/1 HTTP/1.1 

Notice that both HTTP Requests have the same URI, /blog/article/1, the only difference is the HTTP Request verb. And based on that verb your router can call different actionController. This enables you to build neat URL-s.

Read this two articles, they might help you:

Symfony 2 - HTTP Fundamentals

Symfony 2 - Routing

These articles are about Symfony 2 framework, but they can help you to figure out how does HTTP Requests and Responses work.

Hope this helps!