with-xml-output

While SAX events are useful, their generation is sometimes a little annoying, if you attempt to do it manually. So many functions to call! So many attributes to pass!

cxml includes a macro layer centered around CXML:WITH-XML-OUTPUT, which is more structured, and handles the SAX functions for you.

The most important macros and functions are:

CXML:WITH-XML-OUTPUT (handler) &body body	macro

CXML:WITH-ELEMENT (qname)	function
CXML:ATTRIBUTE (name value)	function
CXML:TEXT (str)	function
CXML:UNESCAPED (str)	function
CXML:COMMENT (str)	function

(Others which we won't go into here in detail are: CXML:DOCTYPE, CXML:WITH-NAMESPACE, CXML:WITH-ELEMENT*, and CXML:PROCESSING-INSTRUCTION.)

Example:

CL-USER> (cxml:with-xml-output (cxml:make-string-sink)
           (cxml:with-element "a"
             (cxml:attribute "a" 1)
             (cxml:attribute "b" "c")
             (cxml:text "d & e")))

 0: (SAX:START-DOCUMENT CXML::SINK)
 0: (SAX:START-ELEMENT CXML::SINK NIL "a" "a"
                            (#S(SAX::STANDARD-ATTRIBUTE)
                             #S(SAX::STANDARD-ATTRIBUTE)))
 0: (SAX:CHARACTERS CXML::SINK "t")
 0: (SAX:END-ELEMENT CXML::SINK NIL "a" "a")
 0: (SAX:END-DOCUMENT CXML::SINK)

"<?xml version=\"1.0\" encoding=\"UTF-8\"?>
<a a=\"1\" b=\"c\">d &amp; e</a>"

Points to take away from this:

A macro or functional layer on top of SAX makes it easy to generate SAX events.
The implementation of those macros isn't shown here, but I hope it's clear that the code for that is pretty easy.
I.e. you can write your own convenience layer if you like, and then use it to serialize XML, etc., all without having to actually work with XML serialization and escaping issues.
You can, of course, plug other sinks in there:

CL-USER> (cxml:with-xml-output (make-instance 'upcaser :chained-handler
                                              (stp:make-builder))
           (cxml:with-element "a"
             (cxml:attribute "a" 1)
             (cxml:attribute "b" "c")
             (cxml:text "d & e")))

#.(CXML-STP-IMPL::DOCUMENT
   :CHILDREN '(#.(CXML-STP:ELEMENT
                  :ATTRIBUTES '(#.(CXML-STP:ATTRIBUTE)
                                #.(CXML-STP:ATTRIBUTE))
                  :CHILDREN '(#.(CXML-STP:TEXT :DATA "D & E"))
                  :LOCAL-NAME "a")))