http put和post的区别

PUT	POST
RFC-2616 clearly mention that PUT method requests for the enclosed entity be stored under the supplied Request-URI. If the Request-URI refers to an already existing resource – an update operation will happen, otherwise create operation should happen if Request-URI is a valid resource URI (assuming client is allowed to determine resource identifier).   PUT /questions/{question-id}	The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line. It essentially means that POST request-URI should be of a collection URI.   POST /questions
PUT method is idempotent. So if you send retry a request multiple times, that should be equivalent to single request modification.	POST is NOT idempotent. So if you retry the request N times, you will end up having N resources with N different URIs created on server.
Use PUT when you want to modify a singular resource which is already a part of resources collection. PUT replaces the resource in its entirety. Use PATCH if request updates part of the resource.	Use POST when you want to add a child resource under resources collection.
Though PUT is idempotent, we shall not cache it’s response.	Responses to this method are not cacheable, unless the response includes appropriate Cache-Control or Expires header fields. However, the 303 (See Other) response can be used to direct the user agent to retrieve a cacheable resource.
Generally, in practice, always use PUT for UPDATE operations.	Always use POST for CREATE operations.