request.getHeader("HTTP_REFERER");
or request.getHeader("referer");都可以
可以将获取的URL插入到数据库,以便进行数据挖掘
HTTP1.1规范中的描述
14.36 Referer
The Referer[sic] request-header field allows the client to specify,
for the server's benefit, the address (URI) of the resource from
which the Request-URI was obtained (the "referrer", although the
header field is misspelled.) The Referer request-header allows a
server to generate lists of back-links to resources for interest,
logging, optimized caching, etc. It also allows obsolete or mistyped
links to be traced for maintenance. The Referer field MUST NOT be
sent if the Request-URI was obtained from a source that does not have
its own URI, such as input from the user keyboard.
Referer = "Referer" ":" ( absoluteURI | relativeURI )
Example:
Referer: http://www.w3.org/hypertext/DataSources/Overview.html
If the field value is a relative URI, it SHOULD be interpreted
relative to the Request-URI. The URI MUST NOT include a fragment. See
section 15.1.3 for security considerations.