问题
What\'s the difference between HTTP 301 and 308 status codes?
301(Moved Permanently): This and all future requests should be directed to the given URI.308(Permanent Redirect): The request and all future requests should be repeated using another URI.
They seem to be similar.
回答1:
An overview of 301, 302 and 307
The RFC 7231, the current reference for semantics and content of the HTTP/1.1 protocol, defines the 301 (Moved Permanently) and 302 (Found) status code, that allows the request method to be changed from POST to GET. This specification also defines the 307 (Temporary Redirect) status code that doesn't allow the request method to be changed from POST to GET.
See more details below:
6.4.2. 301 Moved Permanently
The
301(Moved Permanently) status code indicates that the target resource has been assigned a new permanent URI and any future references to this resource ought to use one of the enclosed URIs. [...]Note: For historical reasons, a user agent MAY change the request method from
POSTtoGETfor the subsequent request. If this behavior is undesired, the307(Temporary Redirect) status code can be used instead.
6.4.3. 302 Found
The
302(Found) status code indicates that the target resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client ought to continue to use the effective request URI for future requests. [...]Note: For historical reasons, a user agent MAY change the request method from
POSTtoGETfor the subsequent request. If this behavior is undesired, the307(Temporary Redirect) status code can be used instead.
6.4.7. 307 Temporary Redirect
The
307(Temporary Redirect) status code indicates that the target resource resides temporarily under a different URI and the user agent MUST NOT change the request method if it performs an automatic redirection to that URI. Since the redirection can change over time, the client ought to continue using the original effective request URI for future requests. [...]Note: This status code is similar to
302(Found), except that it does not allow changing the request method fromPOSTtoGET. This specification defines no equivalent counterpart for301(Moved Permanently) (RFC 7238, however, defines the status code308(Permanent Redirect) for this purpose).
The need for 308
The RFC 7238 has been created to define the 308 (Permanent Redirect) status code, that is similar to 301 (Moved Permanently) but does not allows the request method to be changed from POST to GET.
The 308 status code is now defined by the RFC 7538 (that obsoleted the RFC 7238).
3. 308 Permanent Redirect
The
308(Permanent Redirect) status code indicates that the target resource has been assigned a new permanent URI and any future references to this resource ought to use one of the enclosed URIs. Clients with link editing capabilities ought to automatically re-link references to the effective request URI to one or more of the new references sent by the server, where possible. [...]Note: This status code is similar to
301(Moved Permanently), except that it does not allow changing the request method fromPOSTtoGET.
Se we have the following:
+-----------+-----------+
| Permanent | Temporary |
+------------------------------------------------------------+-----------+-----------+
| Allows changing the request method from POST to GET | 301 | 302 |
+------------------------------------------------------------+-----------+-----------+
| Doesn't allow changing the request method from POST to GET | 308 | 307 |
+------------------------------------------------------------+-----------+-----------+
Choosing the most suitable status code
Michael Kropat put together a set of decision charts that helps to determine the best status code for each situation. See the following for 2xx and 3xx status codes:
来源：https://stackoverflow.com/questions/42136829/whats-the-difference-between-http-301-and-308-status-codes