Wenn ein web server auf den Antrag von der Datenbanksuchroutine oder von anderem web client reagiert, besteht die Antwort gew�hnlich einer Statuslinie, einigen Warte�berschriften, einer Leerzeile und aus dem Dokument

Spezifizieren von Status Codes

Wie oben beschrieben, besteht die HTTP Wartestatuslinie der HTTP Version, einem Status Code und aus einer verbundenen Anzeige. Da die Anzeige direkt mit dem Status Code verbunden ist und die HTTP Version durch den Bediener festgestellt wird, mu� alles servlet tun ist, Status Code einzustellen. Die Weise zu tun, die durch die setStatus Methode des HttpServletResponse ist.

Die setStatus Methode nimmt das interne (der Status Code) da ein Argument, aber, anstatt, ausdr�ckliche Zahlen, es zu verwenden, ist zuverl�ssiger freier und, die Konstanten zu verwenden, die in HttpServletResponse definiert werden. Der Name von jedem, das konstant ist, wird von der Standard-HTTP 1.1 Anzeige f�r jedes abgeleitet, das mit einem Pr�fix von Sc konstant, ganz Versalien ist (f�r Status Code) und von R�umen, die zu den Unterstreichen ge�ndert werden. So da die Anzeige f�r 404 nicht gefunden wird, ist die gleichwertige Konstante im HttpServletResponse SC_NOT_FOUND dort sind zwei Ausnahmen jedoch. Aus etwas ungeradem Grund wird die Konstante f�r Code 302 von der HTTP 1.0 Anzeige, nicht die HTTP 1.1 Anzeige abgeleitet, und die Konstante f�r den Code 307 fehlt zusammen.

Den Status Code einzustellen nicht immer bedeutet, da� du nicht die R�ckkehr ein Dokument ben�tigst. Z.B. obgleich die meisten Bediener die kleine �Akte nicht gefundene� Anzeige f�r 404 Antworten erzeugen, konnten servlets diese Antwort besonders anfertigen w�nschen. Jedoch wenn du dies tust, mu�t du sicher sein, response.setStatus zu benennen, bevor Sie irgendeinen Inhalt �ber PrintWriter senden.

Obgleich die allgemeine Methode der Einstellung von Status Codes einfach zum Anruf response.setStatus (intern) ist, gibt es zwei allgemeine F�lle, in denen eine Abk�rzungmethode im HttpServletResponse zur Verf�gung gestellt wird. Die sendError Methode erzeugt die Antwort 404 zusammen mit einer kurzen Anzeige, die innerhalb eines HTML Dokumentes formatiert wird. Und die sendRedirect Methode erzeugt die Antwort 302 zusammen mit einer Position �berschrift, die das URL des neuen Dokumentes anzeigt.

HTTP 1.1 Status Codes und ihre Bedeutung

Das Folgen ist die Liste aller vorhandenen HTTP 1.1 Status Codes, zusammen mit ihrer verbundenen Anzeige und Deutung. Du solltest vorsichtig sein, wenn Sie Status Codes verwenden, die nur in HTTP 1.1 vorhanden sind, da viele Datenbanksuchroutinen noch nur HTTP 1.0 st�tzen. Wenn du die Status Codes verwendest, die zu HTTP 1.1 spezifisch sind, in den meisten F�llen w�nschst du entweder zu �berpr�fst ausdr�cklich die HTTP Version des Antrags (�ber die getProtocol Methode des HttpServletRequest) oder aufhebst sie f�r Situationen, als kein HTTP 1.0 Status Code zum Klienten irgendwie besonders sinnvoll sein w�rde.

Status Code	Associated Message	Meaning
100	Continue	Continue with partial request. (New in HTTP 1.1)
101	Switching Protocols	Server will comply with Upgrade header and change to different protocol. (New in HTTP 1.1)
200	OK	Everything's fine; document follows for GET and POST requests. This is the default for servlets; if you don't use setStatus, you'll get this.
201	Created	Server created a document; the Location header indicates its URL.
202	Accepted	Request is being acted upon, but processing is not completed.
203	Non-Authoritative Information	Document is being returned normally, but some of the response headers might be incorrect since a document copy is being used. (New in HTTP 1.1)
204	No Content	No new document; browser should continue to display previous document. This is a useful if the user periodically reloads a page and you can determine that the previous page is already up to date. However, this does not work for pages that are automatically reloaded via the Refresh response header or the equivalent <META HTTP-EQUIV="Refresh" ...> header, since returning this status code stops future reloading. JavaScript-based automatic reloading could still work in such a case, though.
205	Reset Content	No new document, but browser should reset document view. Used to force browser to clear CGI form fields. (New in HTTP 1.1)
206	Partial Content	Client sent a partial request with a Range header, and server has fulfilled it. (New in HTTP 1.1)
300	Multiple Choices	Document requested can be found several places; they'll be listed in the returned document. If server has a preferred choice, it should be listed in the Location response header.
301	Moved Permanently	Requested document is elsewhere, and the URL for it is given in the Location response header. Browsers should automatically follow the link to the new URL.
302	Found	Similar to 301, except that the new URL should be interpreted as a temporary replacement, not a permanent one. Note: the message was "Moved Temporarily" in HTTP 1.0, and the constant in HttpServletResponse is SC_MOVED_TEMPORARILY, not SC_FOUND.Very useful header, since browsers automatically follow the link to the new URL. This status code is so useful that there is a special method for it, sendRedirect. Using response.sendRedirect(url) has a couple of advantages over doing response.setStatus(response.SC_MOVED_TEMPORARILY) and response.setHeader("Location", url). First, it is easier. Second, with sendRedirect, the servlet automatically builds a page containing the link (to show to older browsers that don't automatically follow redirects). Finally, sendRedirect can handle relative URLs, automatically translating them to absolute ones. Note that this status code is sometimes used interchangeably with 301. some servers will send 301 and others will send 302. Technically, browsers are only supposed to automatically follow the redirection if the original request was GET. See the 307 header for details.
303	See Other	Like 301/302, except that if the original request was POST, the redirected document (given in the Location header) should be retrieved via GET. (New in HTTP 1.1)
304	Not Modified	Client has a cached document and performed a conditional request (usually by supplying an If-Modified-Since header indicating that it only wants documents newer than a specified date). Server wants to tell client that the old, cached document should still be used.
305	Use Proxy	Requested document should be retrieved via proxy listed in Location header. (New in HTTP 1.1)
307	Temporary Redirect	This is identical to 302 ("Found" or "Temporarily Moved"). It was added to HTTP 1.1 since many browsers erroneously followed the redirection on a 302 response even if the original message was a POST, even though it really ought to have followed the redirection of a POST request only on a 303 response. This response is intended to be unambigously clear: follow redirected GET and POST requests in the case of 303 responses, only follow the redirection for GET requests in the case of 307 responses. Note: for some reason there is no constant in HttpServletResponse corresponding to this status code. (New in HTTP 1.1)
400	Bad Request	Bad syntax in the request.
401	Unauthorized	Client tried to access password-protected page without proper authorization. Response should include a WWW-Authenticate header that the browser would use to pop up a username/password dialog box, which then comes back via the Authorization header.
403	Forbidden	Resource is not available, regardless of authorization. Often the result of bad file or directory permissions on the server.
404	Not Found	No resource could be found at that address. This is the standard "no such page" response. This is such a common and useful response that there is a special method for it in HttpServletResponse: sendError(message). The advantage of sendError over setStatus is that, with sendError, the server automatically generates an error page showing the error message.
405	Method Not Allowed	The request method (GET, POST, HEAD, DELETE, PUT, TRACE, etc.) was not allowed for this particular resource. (New in HTTP 1.1)
406	Not Acceptable	Resource indicated generates a MIME type incompatible with that specified by the client via its Accept header. (New in HTTP 1.1)
407	Proxy Authentication Required	Similar to 401, but proxy server must return a Proxy-Authenticate header. (New in HTTP 1.1)
408	Request Timeout	The client took too long to send the request. (New in HTTP 1.1)
409	Conflict	Usually associated with PUT requests; used for situations such as trying to upload an incorrect version of a file. (New in HTTP 1.1)
410	Gone	Document is gone; no forwarding address known. Differs from 404 in that the document is is known to be permanently gone in this case, not just unavailable for unknown reasons as with 404. (New in HTTP 1.1)
411	Length Required	Server cannot process request unless client sends a Content-Length header. (New in HTTP 1.1)
412	Precondition Failed	Some precondition specified in the request headers was false. (New in HTTP 1.1)
413	Request Entity Too Large	The requested document is bigger than the server wants to handle now. If the server thinks it can handle it later, it should include a Retry-After header. (New in HTTP 1.1)
414	Request URI Too Long	The URI is too long. (New in HTTP 1.1)
415	Unsupported Media Type	Request is in an unknown format. (New in HTTP 1.1)
416	Requested Range Not Satisfiable	Client included an unsatisfiable Range header in request. (New in HTTP 1.1)
417	Expectation Failed	Value in the Expect request header could not be met. (New in HTTP 1.1)
500	Internal Server Error	Generic "server is confused" message. It is often the result of CGI programs or (heaven forbid!) servlets that crash or return improperly formatted headers.
501	Not Implemented	Server doesn't support functionality to fulfill request. Used, for example, when client issues command like PUT that server doesn't support.
502	Bad Gateway	Used by servers that act as proxies or gateways; indicates that initial server got a bad response from the remote server.
503	Service Unavailable	Server cannot respond due to maintenance or overloading. For example, a servlet might return this header if some thread or database connection pool is currently full. Server can supply a Retry-After header.
504	Gateway Timeout	Used by servers that act as proxies or gateways; indicates that initial server didn't get a response from the remote server in time. (New in HTTP 1.1)
505	HTTP Version Not Supported	Server doesn't support version of HTTP indicated in request line. (New in HTTP 1.1)