PUT 方法可以插入、删除。 那么为什么我们必须使用 POST 方法而不是 PUT/DELETE/GET 方法

Question

A value can be passed as well retrieved using any of the GET, POST, PUT, DELETE - HTTP verbs. We can even update or delete the data using GET request then why should we use DELETE for deleting a resource?

Also, What's the significance of using a POST method If a PUT method can CREATE as well as UPDATE the record?

Answer 1

You can practically use a POST to do all the CRUD operations but you shouldn't . Because Each HTTP verb has its own responsibility.

A GET is supposed to be idempotent and safe. A GET can be cached and in a browser, refreshed again and again. Ideally, firing a GET request shouldn't change the data.

If HttpGet method can delete, can insert, can update and also can return value then why we use HttpPort, HttpPut and HttpDelete?

Imagine a scenario.

You have a Web API method which adds a new entry to the database using GET. If your GET request becomes a link and it gets crawled by a search engine. You will have your database full of duplicate data. So it makes sense to use POST in this case.

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Selecting The Appropriate Method

GET - requests data from the resource and should not produce any side effect.

POST - method requests the server to create a resource in the database, mostly when a web form is submitted. Post is non-idempotent which means multiple requests will have different effects.

PUT - method requests the server to update a resource or create the resource, if it doesn't exist. Put is idempotent which means multiple requests will have the same effects.

DELETE - method requests that the resources, or its instance, should be removed from the database.

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POST vs PUT

POST and PUT are very similar in that they both send data to the server that the server will need to store somewhere. if you make the same request twice using PUT, with the same parameters both times, the second request will have no effect. This is why PUT is generally used for the Update scenario.

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There are some more limitations for different Http verbs as well.

• GET parameters are passed as part of the URL, which is of small and limited length of 256 chars by default, with some servers supporting 4000+ chars. If you want to insert a long record,you'll have to use POST. Post is considered limitless but there are limitations which vary according to browsers.
• GET is re-executed if a user presses a Back button in a browser. Post doesn't.
• GET is cached by browsers, nodes in the network, Internet Service Providers.
• Unless the content changes, GET to the same URL must return same results to all the users or else you won't have any trust what so ever in the returned result. etc.

Answer 2

Technically the POST method covers all your use cases. Looking at the HTTP request header:

POST /service.aspx HTTP/1.1
Host: test.com&page=2

field1=value1&field2=value2

"field1" and "field2" are POST parameters, "page" is a GET parameter even though it's a POST request.

Not every server supports other methods. The reason for PUT and DELETE is because, semantically, people wanted the web request counterparts of a CRUD. What's the difference between a request that creates a new record, or just one that modifies an existing record? What's the difference between a reading request and one that modifies a record?

The convention is to map the following:

C - New Record - POST
R - Read Record - GET
U - Update Record - PUT
D - Delete Record - DELETE

Answer 3

The actual thing is that you should follow the protocol. Because, other developers have no idea what your function would do, unless the verb is specified. It is just to remove the ambiguity of the API of your application. Otherwise, you can surely do anything.