Status Codes that Indicate the Result of the HTTP Request.

• 1XX   -  Informational

• 2XX   -  Success

• 3XX   -  Redirection

• 4XX   -  Client error

• 5XX   -  Server error

•  public interface HttpServletResponse extends ServletResponse 

•     public static final int SC_CONTINUE                           = 100;

•     public static final int SC_SWITCHING_PROTOCOLS      = 101;

•     public static final int SC_OK                                      = 200;

•     public static final int SC_CREATED                             = 201;

•     public static final int SC_ACCEPTED                           = 202;

•     public static final int SC_NON_AUTHORITATIVE_INFORMATION = 203;

•     public static final int SC_NO_CONTENT                      = 204;

•     public static final int SC_RESET_CONTENT                 = 205;

•     public static final int SC_PARTIAL_CONTENT              = 206;

•     public static final int SC_MULTIPLE_CHOICES             = 300;

•     public static final int SC_MOVED_PERMANENTLY        = 301;

•     public static final int SC_MOVED_TEMPORARILY         = 302;

•     public static final int SC_FOUND                               = 302;

•     public static final int SC_SEE_OTHER                        = 303;

•     public static final int SC_NOT_MODIFIED                   = 304;

•     public static final int SC_USE_PROXY                        = 305;

•     public static final int SC_TEMPORARY_REDIRECT       = 307;

•     public static final int SC_BAD_REQUEST                   = 400;

•     public static final int SC_UNAUTHORIZED                 = 401;

•     public static final int SC_PAYMENT_REQUIRED          = 402;

•     public static final int SC_FORBIDDEN                       = 403;

•     public static final int SC_NOT_FOUND                     = 404;

•     public static final int SC_METHOD_NOT_ALLOWED   = 405;

•     public static final int SC_NOT_ACCEPTABLE              = 406;

•     public static final int SC_PROXY_AUTHENTICATION_REQUIRED = 407;

•     public static final int SC_REQUEST_TIMEOUT            = 408;

•     public static final int SC_CONFLICT                          = 409;

•     public static final int SC_GONE                                = 410;

•     public static final int SC_LENGTH_REQUIRED            = 411;

•     public static final int SC_PRECONDITION_FAILED       = 412;

•     public static final int SC_REQUEST_ENTITY_TOO_LARGE = 413;

•     public static final int SC_REQUEST_URI_TOO_LONG     = 414;

•     public static final int SC_UNSUPPORTED_MEDIA_TYPE = 415;

•     public static final int SC_REQUESTED_RANGE_NOT_SATISFIABLE = 416;

•     public static final int SC_EXPECTATION_FAILED           = 417;

•     public static final int SC_INTERNAL_SERVER_ERROR = 500;

•     public static final int SC_NOT_IMPLEMENTED           = 501;

•     public static final int SC_BAD_GATEWAY                  = 502;

•     public static final int SC_SERVICE_UNAVAILABLE      = 503;

•     public static final int SC_GATEWAY_TIMEOUT          = 504;

•     public static final int SC_HTTP_VERSION_NOT_SUPPORTED = 505;

          # Some times 405 may cause  due  to not having same  request type in, method and request.

• 504 Gateway Timeout   

  This usually means that the other server is down or not working properly. Resolution: The 504            Gateway  Timeout error is usually a network error between servers on the Internet or an issue with an actual server, meaning the problem is not with your PC or Internet connection.

•  304 Not Modified 
     
  is an HTTP status code that is returned to the client when the cached copy of a particular file is up to date with the server. When a client such as a browser stores something in cache, it also keeps the Last-Modified header sent from the server