D 2011-09-23T22:13:19.964
L Creating\sResponses
U murphy
W 2725
<h1>Creating Responses</h1>
Each request handler is expected to return an instance of the <tt>response</tt> structure type that has a SRFI-99 definition similar to the following one:
<verbatim>
(define-record-type (response message)
#f #t
status status-message)
</verbatim>
A <tt>response</tt> is actually a subtype of a <tt>message</tt> (see [Interpreting Parameters]) and inherits its <tt>type</tt>, <tt>headers</tt> and <tt>body</tt> fields. In addition the message specifies the status code and status line message that should be returned to the webserver.
To create a response, you can use any of the following procedures:
<verbatim>
(make-response STATUS BODY [#:type TYPE] [#:headers HEADERS] [#:status-message STATUS-MESSAGE]) => RESPONSE
</verbatim>
Creates a message given a numeric <tt>STATUS</tt> code and a string <tt>BODY</tt>. Optionally you may specify a content <tt>TYPE</tt> (which you probably should, since the default is <tt>application/octet-stream</tt>), additional <tt>HEADERS</tt> or an explicit <tt>STATUS-MESSAGE</tt> (the default is derived from the <tt>STATUS</tt> code).
<verbatim>
(collect-response STATUS THUNK [#:type TYPE] [#:headers HEADERS] [#:status-message STATUS-MESSAGE]) => RESPONSE
</verbatim>
Works similar to <tt>make-response</tt> except that the message body is computed by invoking <tt>THUNK</tt>, which is expected to write the desired content to the current output port.
<verbatim>
(make-html-response STATUS HTML [#:headers HEADERS] [#:status-message STATUS-MESSAGE]) => RESPONSE
</verbatim>
Works similar to <tt>make-response</tt> except that the message body is derived from a HTML5 rendering of the X-expression <tt>HTML</tt>. This expression must be an <tt>ELEMENT</tt> according to the following grammar:
<verbatim>
XEXPR = ELEMENT | CONTENT
ELEMENT = (list SYMBOL (list (list SYMBOL CONTENT ...) ...) XEXPR ...) ;; element optionally with attributes
| (list SYMBOL XEXPR ...) ;; element without attributes
CONTENT = STRING ;; character data
| SYMBOL ;; symbolic entity reference
| INTEGER ;; numeric entity reference
</verbatim>
The content type of the resulting message is <tt>text/html</tt>.
<verbatim>
(make-error-response STATUS MESSAGE [#:headers HEADERS] [#:status-message STATUS-MESSAGE]) => RESPONSE
</verbatim>
Works similar to <tt>make-html-response</tt> but uses a predefined content document into which it only inserts the given error <tt>MESSAGE</tt>.
Z 03938da80112bef94ccc7a798b27268d