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

I have read a lot stuff about this but not able to get the conclusion on this topic.

But I've never used PUT or DELETE HTTP Request methods. My tendency is to use GET when stat of the system(my application or website) may not be affected (like product listing) and to use POST when it is affected(order placed). Isn't it sufficient or am I missing something ?

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!

Safe Methods : Get Resource/No modification in resource
Idempotent : No change in resource status if requested many times
Unsafe Methods : Create or Update Resource/Modification in resource
Non-Idempotent : Change in resource status if requested many times

According to your requirement :

1) For safe and idempotent operation (Fetch Resource) use --------- GET METHOD
2) For unsafe and non-idempotent operation (Insert Resource) use--------- POST METHOD
3) For unsafe and idempotent operation (Update Resource) use--------- PUT METHOD
3) For unsafe and idempotent operation (Delete Resource) use--------- DELETE METHOD

Although I take the risk of not being popular I say they are not useful nowadays.

I think they were well intended and useful in the past when for example DELETE told the server to delete the resource found at supplied URL and PUT (with its sibling PATCH) told the server to do update in an idempotent manner.

Things evolved and URLs became virtual (see url rewriting for example) making resources lose their initial meaning of real folder/subforder/file and so, CRUD action verbs covered by HTTP protocol methods (GET, POST, PUT/PATCH, DELETE) lost track.

Let's take an example:

• /api/entity/list/{id} vs GET /api/entity/{id}
• /api/entity/add/{id} vs POST /api/entity
• /api/entity/edit/{id} vs PUT /api/entity/{id}
• /api/entity/delete/{id} vs DELETE /api/entity/{id}

On the left side is not written the HTTP method, essentially it doesn't matter (POST and GET are enough) and on the right side appropriate HTTP methods are used.

Right side looks elegant, clean and professional. Imagine now you have to maintain a code that's been using the elegant API and you have to search where deletion call is done. You'll search for "api/entity" and among results you'll have to see which one is doing DELETE. Or even worse, you have a junior programmer which by mistake switched PUT with DELETE and as URL is the same shit happened.

In my opinion putting the action verb in the URL has advantages over using the appropriate HTTP method for that action even if it's not so elegant. If you want to see where delete call is made you just have to search for "api/entity/delete" and you'll find it straight away.

Building an API without the whole HTTP array of methods makes it easier to be consumed and maintained afterwards