Response status code

100 continue: the initial request has been accepted, and the customer should continue to send the rest of the request.

101 switching protocols: the server converts a client-compliant request to another protocol.

200 OK: Everything is normal. The response document to the get and post requests follows. If you do not need setstatus to set the status code, the servlet uses the 202 status code by default.

The 201 created server has created a document and the location header provides its URL.

202 accepted: the request has been accepted, but the processing has not been completed.

203 non-authoritative information: the document has been normally returned, but some response headers may be incorrect because the document is copied.

204 NO content: no new document. The browser should continue to display the original document. This status code is useful if the user regularly refreshes the page and the servlet can determine that the user document is new enough.

205 reset content: there is no new content, but the browser should reset the content displayed by it. Used to force the browser to clear the input content of the form.

206 partial content: the client sends a GET request with a range header, and the server completes the request.

300 Multiple choices: the document requested by the customer can be found in multiple locations, which are listed in the returned documents. If the server needs to give priority, it should be specified in the location response header.

301 moved permanently: the document requested by the customer is elsewhere. The new URL is provided in the location header and the browser should automatically access the new URL.

302 found: similar to 301, but the new URL should be treated as a temporary alternative, rather than permanent. Note that the status information in http1.0 is "Moved temporatily", while the constant in httpservletresponse is SC _moved_temporarily, rather than SC _found. When this status code appears, the browser can automatically access the new URL, so it is a very useful status code. To this end, servlet provides a dedicated method, namely sendredirect. Using response. sendredirect (URL) is better than using response. setstatus (response. SC _moved_temporarily) and response. setheader ("location", URL. Note that this status code can be replaced with 301 sometimes.

303 see other: similar to 301/302. The difference is that if the original request is post, the redirection target document specified by the location header should be extracted through get.

304 not modified: the client has a buffered document and issued a conditional request (generally, the IF-modified-since header is provided to indicate that the customer only wants to update the document later than the specified date ). The server tells the customer that the original buffer documentation can still be used.

305 use proxy: the client request document should be extracted from the proxy server specified by the location header.

307 temporary redirect: Same as 302 (found. Many browsers mistakenly respond to the 302 response for redirection. Even if the original request is post, it can only be redirected when the POST request actually responds to 303. For this reason, HTTP 1.1 adds 307 to clear the region code in several states: When a 303 response occurs, the browser can follow the redirected get and post requests. If a 307 response occurs, the browser can only follow the redirection to get requests. Note: No constants are provided for the status code in httpservletresponse.

400 bad request: the request has a syntax error.

401 unauthorized: the customer attempted to access the password-protected page without authorization. The response contains a WWW-Authenticate header. the browser displays the username/password dialog box accordingly, and then sends a request again after entering the appropriate authorization header.

403 Forbidden: the resource is unavailable. The server understands the customer's request, but rejects the request. This is usually caused by permission settings for files or directories on the server.

404 Not found: the resource at the specified position cannot be found. This is also a common response. httpservletresponse provides the corresponding method: senderror (Message ).

405 method not allowed: The request method (get, post, Head, delete, put, Trace, etc.) is not applicable to the specified resource.

406 not acceptable: the specified resource has been found, but its MIME type is incompatible with the one specified by the customer in the accpet header.

407 proxy authentication required: similar to 401, indicates that the customer must first be authorized by the proxy server.

408 request Timeout: the customer has not sent any request within the waiting time permitted by the server. The customer can repeat the same request later.

409 conflict: usually related to put requests. The request cannot be successful because the request conflicts with the current status of the resource.

410 gone: the requested document is no longer available, and the server does not know which address to redirect. It differs from 404 in that if 407 is returned, the document permanently leaves the specified position, and 404 indicates that the document is unavailable for unknown reasons.

411 length required: the server cannot process the request unless the client sends a Content-Length header.

412 precondition failed: Some of the prerequisites specified in the request header fail.

413 Request Entity too large: the size of the target document exceeds the size that the server is willing to process. If the server thinks it can process the request later, it should provide a retry-after header.

414 request URI Too long: The URI is too long.

416 requested range not satisfiable: the server cannot meet the range header specified by the customer in the request.

500 internal server error: the server encounters unexpected circumstances and cannot complete the customer's request.

501 not implemented: the server does not support the functions required to implement the request. For example, the customer sends a put request not supported by the server.

502 Bad Gateway: when the server acts as a gateway or proxy, the server returns an invalid response to access the next server to complete the request.

503 service unavailable: the server fails to respond due to maintenance or overload. For example, Servlet may return 503 when the database connection pool is full. When the server returns 503, A retry-after header can be provided.

504 gateway timeout: used by a proxy or gateway server, indicating that the remote server cannot receive a response in a timely manner.

505 HTTP Version not supported: the server does not support the HTTP Version specified in the request