2008 February 26th Tuesday (二月　二十六日　火曜日）

Sometimes we may wish to avoid brower built-in authentication dialogs altogether.  Since the dialog is automatically triggered
by an HTTP 401 or 407 response, we must avoid sending these codes to the client.  It is not longer sufficient event to send a login
from as ErrorDocument.  Instead, we must either (a) present the unauthenticated user with a login form immediately, or (b) redirect
the unauthenticated user to a login form with an HTTP 302 response.

 Each filter chain (input and output) passes through predefined stages.  Thus the same filter architecture can be used for different
kinds of operation.  In brief, from the content generator to client, we have the following classes of filter:

 Content filters, which process document contents within a request.  These are the filter most commonly relevant to applications
 programming.

 Protocol filters, which deal with details of the protocol but treat the contents as opaque.  These filters are concerned with translating
 between HTTP data(as defined in RFC2616) and Apache's internal representation in the request_rec and associated structures.

 Connection filter, which process a TCP connection without referentce to HTTP (either the protocol ot contents).  These filters are
 concerned with interfacing Apache with the network;  they operate entirely outside the scope of HTTP or of any request_rec.