estudy 한국어/English

3xx - Redirection

881 단어·2 분·원문(.md)

3xx (Redirection) #

Additional action by the user agent is required to complete the request.

  • 300 Multiple choices
  • 301 Moved Permanently
  • 302 Found
  • 303 See Other
  • 304 Not Modified
  • 307 Temporary Redirect
  • 308 Permanent Redirect

Understanding Redirection #

  • If a web browser receives a 3xx response with a Location header, it automatically moves (redirects) to the specified Location.

Automatic Redirection Flow

  1. Request Client -> Server
GET /event HTTP/1.1
Host: localhost:8080
  1. Response -> Server -> Client
HTTP/1.1 301 Moved Permanently
Location: /new-event
  1. Automatic Redirection Client -> Client
  2. Request Client -> Server
GET /new-event HTTP/1.1
Host: localhost:8080
  1. Response -> Client
HTTP/1.1 200 OK

Types #

  • Permanent Redirection - The URI of a specific resource has moved permanently.
    • e.g.) /members -> /users
    • /event -> /new-event
  • Temporary Redirection - A temporary change.
    • Moving to the order history screen after completing an order.
    • PRG : Post/Redirect/Get
  • Special Redirection
    • Using cache instead of result.

Permanent Redirection #

301 , 308 #

  • The URI of the resource has moved permanently.
  • The original URL is no longer used; search engines also recognize the change.
  • 301 Moved Permanently
    • When redirecting, the request method MAY change to GET, and the body MAY be removed.
  • 308 Permanent Redirect
    • Functionality is the same as 301.
    • When redirecting, the request method and body are preserved (if the initial request was POST, the redirection maintains POST).

Permanent Redirection - 301 #

  1. Request Client -> Server, using POST, message present
POST /event HTTP/1.1
Host: localhost:8080

name=hello&ange=20
  1. Response Server -> Client
HTTP/1.1 301 Moved Permanently
Location: /new-event
  1. Automatic Redirection Client -> Client
  2. Request Client -> Server, changed to GET, message removed
GET /new-event HTTP/1.1
Host: localhost:8080
  1. Response Server -> Client
HTTP/1.1 200 OK

Permanent Redirection - 308 #

  1. Request Client -> Server, using POST, message present
POST /event HTTP/1.1
Host: localhost:8080

name=hello&age=20
  1. Response Server -> Client
HTTP/1.1 308 Permanent Redirect
Location: /new-eve
  1. Automatic Redirection Client -> Client
  2. Request Client -> Server
POST /new-event HTTP/1.1
Host: localhost:8080

name=hello&age=20
  1. Response Server -> Client
HTTP/1.1 200 OK

Temporary Redirection 302, 307, 303 #

  • The URI of the resource is temporarily changed.
  • Therefore, search engines should not change the URL.
  • 302 Found
    • When redirecting, the request method MAY change to GET, and the body MAY be removed.
  • 307 Temporary Redirect
    • Functionality is the same as 302.
    • When redirecting, the request method and body are preserved (the request method MUST NOT be changed).
  • 303 See Other
    • Functionality is the same as 302.
    • When redirecting, the request method changes to GET.

PRG Post/Redirect/Get #

Temporary Redirection - Example

  • What happens if you refresh the web browser after ordering with POST?
  • Refreshing is a re-request.
  • This can lead to duplicate orders.

Before using PRG #

  1. Request
POST /order HTTP/1.1
Host: localhost:8080

itemId=mouse&count=1
  1. Save order data: 1 mouse
  2. Response
HTTP/1.1 200 OK

<html>주문완료</html>
  1. Refresh on the result screen
  2. Request
POST /order HTTP/1.1
Host: localhost:8080

itemId=mouse&count=1
  1. Save order data: 1 mouse
  2. Response
HTTP/1.1 200 OK

<html>주문완료</html>

Temporary Redirection - Example #

  • Prevents duplicate orders caused by refreshing after ordering with POST.
  • Redirects to the order result screen with a GET method after ordering with POST.
  • Even if refreshed, the result screen is retrieved with GET.
  • Instead of duplicate orders, only the result screen is re-requested with GET.
  1. Request
POST /order HTTP/1.1
Host: localhost:8080

itemId=mouse&count=1
  1. Save order data: 1 mouse
  2. Response
HTTP/1.1 302 Found
Location: /order-result/19
  1. Refresh on the result screen
  2. Request
GET /order-result/19 HTTP/1.1
Host: localhost:8080
  1. Retrieve order data: order number 19
  2. Response
HTTP/1.1 200 OK	

<html>주문완료</html>
  1. Refresh on the result screen
    • GET /order-result/19
    • Only the result screen is re-requested (moves to step 5).
  • Redirection after PRG
    • The URL has already been redirected from POST -> GET.
    • Even if refreshed, only the result screen is retrieved with GET.

So, what should I use? #

302, 307, 303

  • Quick summary
    • 302 Found -> Can change to GET
    • 307 Temporary Redirect -> Method must not change
    • 303 See Other -> Method changes to GET
  • History
    • The initial intent of the 302 specification was to preserve the HTTP method.
    • However, most web browsers changed it to GET (some behave differently).
    • Thus, clear 307 and 303 emerged to replace the ambiguous 302 (308 also appeared as an alternative to 301).
  • Reality
    • While 307 and 303 are recommended, in reality, many application libraries already use 302 as the default.
    • If it's acceptable for the method to change to GET during automatic redirection, using 302 is generally not a big problem.

Other Redirections #

  • 300 Multiple Choice: Not used.
  • 304 Not Modified
    • Used for caching purposes.
    • Informs the client that the resource has not been modified. Therefore, the client reuses the cached version stored on its local PC (redirects to the cache).
    • A 304 response MUST NOT contain a message body (because the local cache should be used).
    • Used with conditional GET and HEAD requests.
Back-End/http/HTTP상태코드/3xx.md