HTTP response header Information

HTTP Response header Information

The HTTP request header provides information about the request, response, or other sending entity.

In this section we will cover HTTP response header information specifically.

Answer Header	Description
Allow	Which request methods are supported by the server (such as GET, post, etc.).
Content-encoding	The encoding (Encode) method of the document. The content type specified by the Content-type header can be obtained only after decoding. Using gzip to compress documents can significantly reduce the download time of HTML documents. Java's gzipoutputstream can be easily gzip compressed, but only on Unix Netscape and IE 4, ie 5 on Windows. Therefore, the servlet should check whether the browser supports gzip by looking at the accept-encoding header (that is, Request.getheader ("accept-encoding")). Returns the gzip-compressed HTML page for a browser that supports gzip, returning a normal page for another browser.
Content-length	Represents the content length. This data is only required if the browser is using a persistent HTTP connection. If you want to take advantage of the persistent connection, you can write the output document to Bytearrayoutputstream, look at its size when done, then put that value into the Content-length header and finally pass the Bytearraystream.writeto ( Response.getoutputstream () Send content.
Content-type	Indicates what MIME type the following document belongs to. The servlet defaults to Text/plain, but it usually needs to be explicitly specified as text/html. Because Content-type is often set up, HttpServletResponse provides a dedicated method setContentType.
Date	The current GMT time. You can use Setdateheader to set this header to avoid the hassle of converting the time format.
Expires	When should I think that the document has expired so that it is no longer cached?
Last-modified	The last modification time of the document. The customer can provide a date through the If-modified-since request header, which is treated as a conditional get, and only documents that have been modified later than the specified time are returned, otherwise a 304 (not Modified) state is returned. Last-modified can also be set using the Setdateheader method.
Location	Indicates where the customer should go to extract the document. Location is usually not set directly, but by HttpServletResponse's Sendredirect method, which sets the status code to 302.
Refresh	Indicates how much time the browser should refresh the document, in seconds. In addition to refreshing the current document, you can also pass SetHeader ("Refresh", "5; Url=http://host/path ") lets the browser read the specified page. Note This functionality is usually done by setting the HTML page in the head area of the Note that the meaning of refresh is "refresh this page after n seconds or visit the specified page" instead of "refresh this page every n seconds or visit the specified page". Therefore, continuous refresh requires a refresh header to be sent each time, and sending a 204 status code prevents the browser from continuing to refresh, whether it is using the refresh header or the Note that the refresh header is not part of the HTTP 1.1 formal specification, but rather an extension, but both Netscape and IE support it.
Server	Server name. The servlet generally does not set this value, but is set by the Web server itself.
Set-cookie	Sets the cookie associated with the page. The servlet should not use Response.setheader ("Set-cookie", ...), but should use the dedicated method Addcookie provided by HttpServletResponse. See below for a discussion of cookie settings.
Www-authenticate	What type of authorization information should the customer provide in the authorization header? This header is required in an answer that contains a 401 (unauthorized) status line. For example, Response.setheader ("Www-authenticate", "BASIC realm=\" Executives\ ""). Note that the servlet generally does not handle this, but instead gives the Web server a special mechanism to control access to password-protected pages (for example,. htaccess).

HTTP response header Information