497 lines
20 KiB
HTML
497 lines
20 KiB
HTML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
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<head>
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<title>Closure XML</title>
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<link rel="stylesheet" type="text/css" href="cxml.css"/>
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</head>
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<body>
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<div class="sidebar">
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</div>
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<h1>Using the SAX parser</h1>
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<a name="parser"/>
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<h3>Parsing and Validating</h3>
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<p>
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CXML is implemented as a SAX parser. (Refer to <a
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href="dom.html#parser">make-dom-builder</a> for information about
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DOM.)
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</p>
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<p>
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<div class="def">Function CXML:PARSE-FILE (pathname handler &key ...)</div>
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<div class="def">Function CXML:PARSE-STREAM (stream handler &key ...)</div>
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<div class="def">Function CXML:PARSE-OCTETS (octets handler &key ...)</div>
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Parse an XML document.
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Return values from this function depend on the SAX handler used.<br/>
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Arguments:
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</p>
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<ul>
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<li><tt>pathname</tt> -- a Common Lisp pathname</li>
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<li><tt>stream</tt> -- a Common Lisp stream with element-type
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<tt>(unsigned-byte 8)</tt></li>
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<li><tt>octets</tt> -- an <tt>(unsigned-byte 8)</tt> array</li>
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<li><tt>handler</tt> -- a SAX handler</li>
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</ul>
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<p>
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Common keyword arguments:
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</p>
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<ul>
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<li>
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<tt>validate</tt> -- A boolean. Defaults to
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<tt>nil</tt>. If true, parse in validating mode, i.e. assert that
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the document contains a DOCTYPE declaration and conforms to the
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DTD declared.
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</li>
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<li>
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<tt>dtd</tt> -- unless <tt>nil</tt>, an extid instance
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specifying the external subset to load. This options overrides
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the extid specified in the document type declaration, if any.
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See below for <tt>make-extid</tt>. This option is useful
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for verification purposes together with the <tt>root</tt>
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and <tt>disallow-internal-subset</tt> arguments.
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</li>
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<li><tt>root</tt> -- the expected root element
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name, or <tt>nil</tt> (the default).
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</li>
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<li>
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<tt>entity-resolver</tt> -- <tt>nil</tt> or a function of two
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arguments which is invoked for every entity referenced by the
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document with the entity's Public ID (a rod) and System ID (an
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URI object) as arguments. The function may either return
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nil, CXML will then try to resolve the entity as usual.
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Alternatively it may return a Common Lisp stream specialized on
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<tt>(unsigned-byte 8)</tt> which will be used instead. (It may
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also signal an error, of course, which can be useful to prohibit
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parsed XML documents from including arbitrary files readable by
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the parser.)
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</li>
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<li>
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<tt>disallow-internal-subset</tt> -- a boolean. If true, signal
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an error if the document contains an internal subset.
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</li>
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<li>
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<tt>recode</tt> -- a boolean. (Ignored on Lisps with Unicode
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support.) Recode rods to UTF-8 strings. Defaults to true.
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Make sure to use <tt>utf8-dom:make-dom-builder</tt> if this
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option is enabled and <tt>rune-dom:make-dom-builder</tt>
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otherwise.
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</li>
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</ul>
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<p>
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<div class="def">Function CXML:PARSE-DTD-FILE (pathname)</div>
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<div class="def">Function CXML:PARSE-DTD-STREAM (stream)</div>
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Parse <a
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href="http://www.w3.org/TR/2000/REC-xml-20001006#NT-extSubset">declarations</a>
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from a stand-alone file and return an object representing the DTD,
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suitable as an argument to <tt>validate</tt>.
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</p>
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<ul>
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<li><tt>pathname</tt> -- a Common Lisp pathname</li>
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<li><tt>stream</tt> -- a Common Lisp stream with element-type
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<tt>(unsigned-byte 8)</tt></li>
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</ul>
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<p>
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<div class="def">Function CXML:MAKE-EXTID (publicid systemid)</div>
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Create an object representing the External ID composed
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of the specified Public ID, a rod or <tt>nil</tt>, and System ID
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(an URI object).
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</p>
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<p>
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<div class="def">Condition class CXML:XML-PARSE-ERROR ()</div>
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Superclass of all conditions signalled by the CXML parser.
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</p>
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<p>
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<div class="def">Condition class CXML:WELL-FORMEDNESS-VIOLATION (cxml:xml-parse-error)</div>
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This condition is signalled for all well-formedness violations.
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(Note that, when parsing document that is not well-formed in validating
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mode, the parser might encounter validity errors before detecting
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well-formedness problems, so also be prepared for <tt>validity-error</tt>
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in that situation.)
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</p>
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<p>
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<div class="def">Condition class CXML:VALIDITY-ERROR (cxml:xml-parse-error)</div>
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Reports the violation of a validity constraint.
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</p>
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<a name="serialization"/>
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<h3>Serialization</h3>
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<p>
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Serialization is performed using <tt>sink</tt> objects. A sink
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is an output stream for runes. There are different kinds of sinks
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for output to lisp streams, vectors, etc.
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</p>
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<p>
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Technically, sinks are SAX handlers that write XML output for SAX
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events sent to them. In practise, user code would normally not
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generate those SAX events manually, and instead use a function
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like <a href="dom.html#serialization">dom:map-document</a> or <a
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href="xmls-compat.html">xmls-compat:map-node</a> to serialize an
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in-memory document.
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</p>
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<p>
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In addition to <tt>map-document</tt>, cxml has a set of
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convenience macros for serialization (see below for
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<tt>with-xml-output</tt>, <tt>with-element</tt>, etc).
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</p>
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<p>
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<div class="def">Function CXML:MAKE-CHARACTER-STREAM-SINK (stream &rest keys) => sink</div>
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<div class="def">Function CXML:MAKE-OCTET-VECTOR-SINK (&rest keys) => sink</div>
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Return a handle suitable for event-based XML serialization.
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</p>
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<p>Keyword arguments:</p>
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<ul>
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<li>
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<tt>canonical</tt> -- canonical form, one of NIL, T, 1, 2
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</li>
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<li>
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<tt>indentation</tt> -- indentation level. An integer or <tt>nil</tt>.
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</li>
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</ul>
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<p>
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The following <tt>canonical</tt> values are allowed:
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</p>
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<ul>
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<li>
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<tt>t</tt> or <tt>1</tt>: <a
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href="http://www.w3.org/TR/2001/REC-xml-c14n-20010315">Canonical
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XML</a>
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</li>
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<li>
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<tt>2</tt>: <a
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href="http://dev.w3.org/cvsweb/~checkout~/2001/XML-Test-Suite/xmlconf/sun/cxml.html?content-type=text/html;%20charset=iso-8859-1">Second
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Canonical Form</a>
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</li>
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<li>
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<tt>NIL</tt>: Use a more readable non-canonical representation.
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</li>
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</ul>
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<p>
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With an <tt>indentation</tt> level, pretty-print the XML by
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inserting additional whitespace. Note that indentation
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changes the document model and should only be used if whitespace
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does not matter to the application.
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</p>
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<p>
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If namespace support is enabled (the default), these functions use
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a namespace normalizer (<tt>cxml:make-namespace-normalizer</tt>).
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</p>
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<p>
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<tt>unparse-document-to-octets</tt> returns an <tt>(unsigned-byte
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8)</tt> array, whereas <tt>unparse-document</tt> writes
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characters. <tt>unparse-document</tt> is useful together
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with <tt>with-output-to-string</tt>. However, note that the
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resulting document in both cases is UTF-8 encoded, so the
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characters written by <tt>unparse-document</tt> are really UTF-8
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bytes encoded as characters.
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</p>
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<p>
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These function provide the low-level mechanism used by the DOM
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serialization functions. To serialize a document without building
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its DOM tree first, create a sink handle and call SAX functions on that
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handle. <tt>sax:end-document</tt> returns the serialized form of
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the document described by the SAX events.
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</p>
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<p>
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<div class="def">Macro CXML:WITH-XML-OUTPUT (sink &body body) => sink-specific result</div>
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<div class="def">Macro CXML:WITH-ELEMENT (qname &body body) => result</div>
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<div class="def">Function CXML:ATTRIBUTE (name value) => value</div>
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<div class="def">Function CXML:TEXT (data) => data</div>
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<div class="def">Function CXML:CDATA (data) => data</div>
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Convenience syntax for event-based serialization.
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</p>
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<p>
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Example:
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</p>
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<pre>(with-xml-output (make-octet-stream-sink stream :indentation 2 :canonical nil)
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(with-element "foo"
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(attribute "xyz" "abc")
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(with-element "bar"
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(attribute "blub" "bla"))
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(text "Hi there.")))</pre>
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<p>
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Prints this to <tt>stream</tt>, which must be an
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<tt>(unsigned-byte 8)</tt> stream:
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</p>
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<pre><foo xyz="abc">
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<bar blub="bla"></bar>
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Hi there.
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</foo></pre>
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<p>
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(Note that these functions accept both strings and rods, so we
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can write <tt>"foo"</tt> instead of <tt>#"foo"</tt> above.)
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</p>
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<p>
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<div class="def">Macro XHTML-GENERATOR:WITH-XHTML (sink &rest forms)</div>
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<div class="def">Macro XHTML-GENERATOR:WRITE-DOCTYPE (sink)</div>
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Macro <tt>with-xhtml</tt> is a modified version of
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Franz' <tt>htmlgen</tt> works as a SAX driver for XHTML.
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It aims to be a plug-in replacement for the <tt>html</tt> macro.
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</p>
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<p>
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<tt>xhtmlgen</tt> is included as <tt>contrib/xhtmlgen.lisp</tt> in
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the cxml distribution. Example:
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</p>
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<pre>(let ((sink (cxml:make-character-stream-sink *standard-output*)))
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(sax:start-document sink)
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(xhtml-generator:write-doctype sink)
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(xhtml-generator:with-html sink
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(:html
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(:head
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(:title "Titel"))
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(:body
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((:p "style" "font-weight: bold")
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"Inhalt")
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(:ul
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(:li "Eins")
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(:li "Zwei")
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(:li "Drei")))))
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(sax:end-document sink))</pre>
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<a name="misc"/>
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<h3>Miscellaneous SAX handlers</h3>
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<p>
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<div class="def">Function CXML:MAKE-VALIDATOR (dtd root)</div>
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Create a SAX handler which validates against a DTD instance.
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The document's root element must be named <tt>root</tt>.
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Used with <tt>dom:map-document</tt>, this validates a document
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object as if by re-reading it with a validating parser, except
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that declarations recorded in the document instance are completely
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ignored.<br/>
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Example:
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</p>
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<pre>(let ((d (parse-file "~/test.xml" (cxml-dom:make-dom-builder)))
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(x (parse-dtd-file "~/test.dtd")))
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(dom:map-document (cxml:make-validator x #"foo") d))</pre>
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<p>
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<div class="def">Class CXML:SAX-PROXY ()</div>
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<div class="def">Accessor CXML:PROXY-CHAINED-HANDLER</div>
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<tt>sax-proxy</tt> is a SAX handler which passes all events it
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receives on to a user-defined second handler, which defaults
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to <tt>nil</tt>. Use <tt>sax-proxy</tt> to modify the events a
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SAX handler receives by defining your own subclass
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of <tt>sax-proxy</tt>. Setting the chained handler to the target
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handler, and define methods on your handler class for the events
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to be modified. All other events will pass through to the chained
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handler unmodified.
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</p>
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<p>
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<div class="def">Accessor CXML:MAKE-NAMESPACE-NORMALIZER (next-handler)</div>
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</p>
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<p>
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Return a SAX handler that performs <a
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href="http://www.w3.org/TR/2004/REC-DOM-Level-3-Core-20040407/namespaces-algorithms.html#normalizeDocumentAlgo">DOM
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3-style namespace normalization</a> on attribute lists in
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<tt>start-element</tt> events before passing them on the next
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handler.
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</p>
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<a name="rods"/>
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<h3>Recoders</h3>
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<p>
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Recoders are a mechanism used by CXML internally on Lisp implementations
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without Unicode support to recode UTF-16 vectors (rods) of
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integers (runes) into UTF-8 strings.
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</p>
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<p>
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User code does not usually need to deal with recoders in current
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versions of CXML.
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</p>
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<p>
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<div class="def">Function CXML:MAKE-RECODER (chained-handler recoder-fn)</div>
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Return a SAX handler which passes all events on to
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<tt>chained-handler</tt> after converting all strings and rods
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using <tt>recoder-fn</tt>, a function of one argument.
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</p>
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<a name="dtdcache"/>
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<h3>Caching of DTD Objects</h3>
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<p>
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To avoid spending time parsing the same DTD over and over again,
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CXML can cache DTD objects. The parser consults
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<tt>cxml:*dtd-cache*</tt> whenever it is looking for an external
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subset in a document which does not have an internal subset and
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uses the cached DTD instance if one is present in the cache for
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the System ID in question.
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</p>
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<p>
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Note that DTDs do not expire from the cache automatically.
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(Future versions of CXML might introduce automatic checks for
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outdated DTDs.)
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</p>
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<p>
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<div class="def">Variable CXML:*DTD-CACHE*</div>
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The DTD cache object consulted by the parser when it needs a DTD.
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</p>
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<p>
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<div class="def">Function CXML:MAKE-DTD-CACHE ()</div>
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Return a new, empty DTD cache object.
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</p>
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<p>
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<div class="def">Variable CXML:*CACHE-ALL-DTDS*</div>
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If true, instructs the parser to enter all DTDs that could have
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been cached into <tt>*dtd-cache*</tt> if they were not cached
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already. Defaults to <tt>nil</tt>.
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</p>
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<p>
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<div class="def">Reader CXML:GETDTD (uri dtd-cache)</div>
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Return a cached instance of the DTD at <tt>uri</tt>, if present in
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the cache, or <tt>nil</tt>.
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</p>
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<p>
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<div class="def">Writer CXML:GETDTD (uri dtd-cache)</div>
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Enter a new value for <tt>uri</tt> into <tt>dtd-cache</tt>.
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</p>
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<p>
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<div class="def">Function CXML:REMDTD (uri dtd-cache)</div>
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Ensure that no DTD is recorded for <tt>uri</tt> in the cache and
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return true if such a DTD was present.
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</p>
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<p>
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<div class="def">Function CXML:CLEAR-DTD-CACHE (dtd-cache)</div>
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Remove all entries from <tt>dtd-cache</tt>.
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</p>
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<p>
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<em>fixme:</em> thread-safety
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</p>
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<a name="catalogs"/>
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<h3>XML Catalogs</h3>
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<p>
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External entities (for example, DTDs) are referred to using their
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Public and System IDs. Usually the System ID, a URI, is used to
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locate the entity. CXML itself handles only file://-URIs, but
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many System IDs in practical use are http://-URIs. There are two
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different mechanims applications can use to allow CXML to locate
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entities using arbitrary Public ID or System ID:
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</p>
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<ul>
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<li>
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User-defined entity resolvers can be used to open entities using
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arbitrary protocols. For example, an entity resolver could
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handle all System-IDs with the <tt>http</tt> scheme using some
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HTTP library. Refer to the description of the
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<tt>entity-resolver</tt> keyword argument to parser functions (see <a
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href="#parser"><tt>cxml:parse-file</tt></a>) to more
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information on entity resolvers.
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</li>
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<li>
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XML Catalogs are (local) tables in XML syntax which map External
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IDs to alternative System IDs. If, say, the xhtml DTD is
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present in the local file system and the local copy has been
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registered with the XML catalog, CXML will use the local copy of
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the DTD instead of trying to open the version available using HTTP.
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</li>
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</ul>
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<p>
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This section describes XML Catalogs, the second solution. CXML
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implements <a
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href="http://www.oasis-open.org/committees/entity/spec.html">Oasis
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XML Catalogs</a>.
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</p>
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<p>
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<div class="def">Variable CXML:*CATALOG*</div>
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The XML Catalog object consulted by the parser before trying to
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open an entity. Initially <tt>nil</tt>.
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</p>
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<p>
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<div class="def">Variable CXML:*PREFER*</div>
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The default "prefer" mode from the Catalog specification, one
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of <tt>:public</tt> or <tt>:system</tt>. Defaults
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to <tt>:public</tt>.
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</p>
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<p>
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<div class="def">Function CXML:MAKE-CATALOG (&optional uris)</div>
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Return a catalog object for the catalog files specified.
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</p>
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<p>
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<div class="def">Function CXML:RESOLVE-URI (uri catalog)</div>
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Look up <tt>uri</tt> in <tt>catalog</tt> and return the
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resulting URI, or <tt>nil</tt> if no match was found.
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</p>
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<p>
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<div class="def">Function CXML:RESOLVE-EXTID (publicid systemid catalog)</div>
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Look up the External ID (<tt>publicid</tt>, <tt>systemid</tt>)
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in <tt>catalog</tt> and return the resulting URI, or <tt>nil</tt>
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if no match was found.
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</p>
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<p>
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Example:
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</p>
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<pre>* (setf cxml:*catalog* nil)
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* (cxml:parse-file "test.xhtml" nil)
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=> Error: URI scheme :HTTP not supported
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* (setf cxml:*catalog* (cxml:make-catalog))
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* (cxml:parse-file "test.xhtml" nil)
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;; no error!
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NIL</pre>
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<p>
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Note that parsed catalog files are cached in the catalog object.
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Catalog files cached do not expire automatically. To ensure that
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all catalog files are parsed again, create a new catalog object.
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</p>
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<a name="sax"/>
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<h2>SAX Interface</h2>
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<p>
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A SAX handler is an arbitrary objects that implements some of the
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generic functions in the SAX package. Note that no default
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handler class is necessary, because all generic functions have default
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methods which do nothing. SAX functions are:
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<div class="def">Function SAX:START-DOCUMENT (handler)</div>
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<div class="def">Function SAX:END-DOCUMENT (handler)</div>
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<br/>
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<div class="def">Function SAX:START-ELEMENT (handler namespace-uri local-name qname attributes)</div>
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<div class="def">Function SAX:END-ELEMENT (handler namespace-uri local-name qname)</div>
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<div class="def">Function SAX:START-PREFIX-MAPPING (handler prefix uri)</div>
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<div class="def">Function SAX:END-PREFIX-MAPPING (handler prefix)</div>
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<div class="def">Function SAX:PROCESSING-INSTRUCTION (handler target data)</div>
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<div class="def">Function SAX:COMMENT (handler data)</div>
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<div class="def">Function SAX:START-CDATA (handler)</div>
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<div class="def">Function SAX:END-CDATA (handler)</div>
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<div class="def">Function SAX:CHARACTERS (handler data)</div>
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<br/>
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<div class="def">Function SAX:START-DTD (handler name public-id system-id)</div>
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<div class="def">Function SAX:END-DTD (handler)</div>
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<div class="def">Function SAX:START-INTERNAL-SUBSET (handler)</div>
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<div class="def">Function SAX:END-INTERNAL-SUBSET (handler)</div>
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<div class="def">Function SAX:UNPARSED-ENTITY-DECLARATION (handler name public-id system-id notation-name)</div>
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<div class="def">Function SAX:EXTERNAL-ENTITY-DECLARATION (handler kind name public-id system-id)</div>
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<div class="def">Function SAX:INTERNAL-ENTITY-DECLARATION (handler kind name value)</div>
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<div class="def">Function SAX:NOTATION-DECLARATION (handler name public-id system-id)</div>
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<div class="def">Function SAX:ELEMENT-DECLARATION (handler name model)</div>
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<div class="def">Function SAX:ATTRIBUTE-DECLARATION (handler ename aname type default)</div>
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<br/>
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<div class="def">Accessor SAX:ATTRIBUTE-PREFIX (attribute)</div>
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<div class="def">Accessor SAX:ATTRIBUTE-NAMESPACE-URI (attribute)</div>
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<div class="def">Accessor SAX:ATTRIBUTE-LOCAL-NAME (attribute)</div>
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<div class="def">Accessor SAX:ATTRIBUTE-QNAME (attribute)</div>
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<div class="def">Accessor SAX:ATTRIBUTE-SPECIFIED-P (attribute)</div>
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<div class="def">Accessor SAX:ATTRIBUTE-VALUE (attribute)</div>
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</p>
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<p>
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The entity declaration methods are similar to Java SAX
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definitions, but parameter entities are distinguished from
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general entities not by a <tt>%</tt> prefix to the name, but by
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the <tt>kind</tt> argument, either <tt>:parameter</tt> or
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<tt>:general</tt>.
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</p>
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<p>
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The arguments to <tt>sax:element-declaration</tt> and
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<tt>sax:attribute-declaration</tt> differ significantly from their
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Java counterparts.
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</p>
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<p>
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<i>fixme</i>: For more information on these functions refer to the docstrings.
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</p>
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</body>
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</html>
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