CS651

HTTP Response Header Status Codes

HTTP/1.1 200 OK
Content-Type: text/plain

Hello Class

HTTP Response STATUS CODES:

Servlet can create a status line to return in its HTTP response by invoking

HttpServletResponse.setStatus(int)
This only specifies the status code, as the protocol and version are determine by the server and created automatically in the response
method takes an int for the code. Can use constants defined in HttpServletResponse.
MUST do before sending any headers and the data itself !!!!!

ALSO, there are two special methods you can use for status codes dealing with errors (e.g. 404) and redirection (303):

HttpServletResponse.sendError(int, String message);
HttpServletResponse.sendRedirect(String url);

NOTE: You may never create a status line in your Servlet's fabricated response!!! This is because there is a default status code (200) that is sent by a Servlet automatically....which says everything was successful!!!!
General groupings of codes

100-199: informational, client shour respond with some other action
200-299: request was successful
300-399: requested files have moved, often will respond with a Location header following that tells where the new location is.
400-499: Error by client
500-599: Error by server

HttpServletResponse Status Code Variables and Meaning
see reading and www.rfc-editor.org (look for RFC 2616) for more codes

100 (SC_CONTINUE)	Server Responds with this code when it has recieved a request from client with Request header Except and value 100-Continue This means that the client has requested to send a follow-up request. 100 server status code response tells client to go ahead are send the follow-up request.
417(Expectation Failed)	Server Responds with this code when it has recieved a request from client with Request header Except and value 100-Continuee This means that the client has requested to send a follow-up request. 417 server status code response tells client it will not accept any further follow-up requests.
101 (SC_SWITCHING_PROTOCOLS)	server will comply with a HTTP request header Upgrade, that asks it to change to a different protocol to communicate with client.
200 (SC_OK)	server responds with this to tell client that the request was successful. Usually following a GET, POST request. this is the default. for Servlet. So, you do not have to set in Servlet.
201 (SC_CREATED)	Server has created new document and the location is given by the HTTP response header LOCATION to follow.
202 (SC_ACCEPTED)	Server tells client that they are processing the request but, are not finished yet.
204 (SC_NO_CONTENT)	Server tells client browser to continue to display previous document as no new document is being sent.
205 (SC_RESET_CONTENT)	Server tells client that no new document comming, but, please refresh current document. Usefull to get HTML forms to clear,etc.
206 (SC_PARTIAL_CONTENT)	Server says the following data is only part of the data to come.
300 (SC_MULTIPLE_CHOICES)	Server says the requested document can be found in several places, which will be returned in the data the server is sending If there is a following HTTP response LOCATION header, this will specified the preferred choice
301 (SC_MOVED_PERMANENTLY)	Server tells client that the document requested has permanetly moved. Must send an HTTP response header LOCATION that gives the new location.
302 (SC_MOVED_TEMPORARILY)	same as 301 but, location in LOCATION response header is a temporary location, not a premanent position.
304 (SC_NOT_MODIFIED)	Response to give to say that the document has not change. A response to a client request which has the HTTP Request Header IF-MODIFIED-SINCE in it....which means the client is asking to send the requested document only if it is newer that the specified time in this header.
305 (SC_USE_PROXY)	Server is telling client that the requested document can only be retrieved using the proxy listed in the HTTP Response Header LOCATION.
401 (SC_UNAUTHORIZED)	Server telling client thehy are trying to access a password-protected page without proper id info in the HTTP request AUTHORIZATION header. You must also send an HTTP response header of WWW_Authenticate
403 (SC_FORBIDDEN)	Server refuses to fulfill the request. Often used because bad file permissions.
404 (SC_NOT_FOUND)	Server can not find the resource reqeusted.
500 (SC_INTERNAL_SERVER_ERROR)	Means servlet or CGI program, etc. has failed.