HTTP Request Methods
The Hypertext Transfer Protocol (HTTP) is designed to enable communications between clients and servers.
HTTP works as a request-response protocol between a client and server.
例子: A client (browser) sends an HTTP request to the server; then the server returns a response to the client. The response contains status information about the request and may also contain the requested content.
The two most common HTTP methods are: GET and POST.
The GET Method
GET is used to request data from a specified resource.
GET is one of the most common HTTP methods.
Note that the query string (name/value pairs) is sent in the URL of a GET request:
Some other notes on GET requests:
- GET requests can be cached
- GET requests remain in the browser history
- GET requests can be bookmarked
- GET requests should never be used when dealing with sensitive data
- GET requests have length restrictions
- GET requests are only used to request data (not modify)
The POST Method
POST is used to send data to a server to create/update a resource.
The data sent to the server with POST is stored in the request body of the HTTP request:
POST is one of the most common HTTP methods.
Some other notes on POST requests:
- POST requests are never cached
- POST requests do not remain in the browser history
- POST requests cannot be bookmarked
- POST requests have no restrictions on data length
The PUT Method
PUT is used to send data to a server to create/update a resource.
The difference between POST and PUT is that PUT requests are idempotent. That is, calling the same PUT request multiple times will always produce the same result. In contrast, calling a POST request repeatedly have side effects of creating the same resource multiple times.
The HEAD Method
HEAD is almost identical to GET, but without the response body.
In other words, if GET /users returns a list of users, then HEAD /users will make the same request but will not return the list of users.
HEAD requests are useful for checking what a GET request will return before actually making a GET request - like before downloading a large file or response body.
The DELETE Method
The DELETE method deletes the specified resource.
The OPTIONS Method
The OPTIONS method describes the communication options for the target resource.
Compare GET vs. POST
The following table compares the two HTTP methods: GET and POST.
|BACK button/Reload||Harmless||Data will be re-submitted (the browser should alert the user that the data are about to be re-submitted)|
|Bookmarked||Can be bookmarked||Cannot be bookmarked|
|Cached||Can be cached||Not cached|
|Encoding type||application/x-www-form-urlencoded||application/x-www-form-urlencoded or multipart/form-data. Use multipart encoding for binary data|
|History||Parameters remain in browser history||Parameters are not saved in browser history|
|Restrictions on data length||Yes, when sending data, the GET method adds the data to the URL; and the length of a URL is limited (maximum URL length is 2048 characters)||No restrictions|
|Restrictions on data type||Only ASCII characters allowed||No restrictions. Binary data is also allowed|
|Security||GET is less secure compared to POST because data sent is part of the URL
Never use GET when sending passwords or other sensitive information!
|POST is a little safer than GET because the parameters are not stored in browser history or in web server logs|
|Visibility||Data is visible to everyone in the URL||Data is not displayed in the URL|