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authorErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
committerErlang/OTP <[email protected]>2009-11-20 14:54:40 +0000
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The R13B03 release.OTP_R13B03
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+
+<meta http-equiv="Context-Type" content="text/html; charset=iso-8859-1">
+<?xml version="1.0" encoding="iso-8859-1"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
+ "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">
+<html xmlns="http://www.w3.org/1999/xhtml" ><head><title>XSLT like transformations in Erlang </title><style type="text/css"> body {margin-left:10%; margin-right:5%;}
+.logo{float:right;}
+.toc UL {
+ list-style-type: none;
+ border: solid;
+ border-width: thin;
+ padding-left: 10px;
+ padding-right: 10px;
+ padding-top: 5px;
+ padding-bottom: 5px;
+ background: #f0f0f0;
+ letter-spacing: 2px;
+ line-height: 20px;
+}
+</style></head><body>
+<h3 id="sect_4.2">Examples</h3>
+ <hr />
+ <h4>Example 1 Using xslapply</h4>
+ <p>original XSLT:</p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+ &lt;xsl:template match="doc/title">
+ &lt;h1>
+ &lt;xsl:apply-templates/>
+ &lt;/h1>
+ &lt;/xsl:template>
+
+ </code></pre></td></tr></table>
+ <p>
+ becomes in Erlang:</p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+ template(E = #xmlElement{ parents=[{'doc',_}|_], name='title'}) ->
+ ["&lt;h1>",
+ xslapply(fun template/1, E),
+ "&lt;/h1>"];
+
+ </code></pre></td></tr></table>
+
+ <hr />
+ <hr />
+ <h4>Example 2 Using value_of and select</h4>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+ &lt;xsl:template match="title">
+ &lt;div align="center">&lt;h1>&lt;xsl:value-of select="." />&lt;/h1>&lt;/div>
+ &lt;/xsl:template>
+
+ </code></pre></td></tr></table>
+ <p>
+ becomes:
+ </p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+template(E = #xmlElement{name='title'}) ->
+ ["&lt;div align=\"center\">&lt;h1>", value_of(select(".", E)), "&lt;/h1>&lt;/div>"];
+
+ </code></pre></td></tr></table>
+ <hr />
+ <hr />
+ <h4>Example 3 Simple xsl stylesheet</h4>
+<p>
+ A complete example with the XSLT sheet in the xmerl distribution.
+</p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+
+&lt;xsl:stylesheet version="1.0"
+ xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+ xmlns="http://www.w3.org/TR/xhtml1/strict">
+
+ &lt;xsl:strip-space elements="doc chapter section"/>
+ &lt;xsl:output
+ method="xml"
+ indent="yes"
+ encoding="iso-8859-1"
+ />
+
+ &lt;xsl:template match="doc">
+ &lt;html>
+ &lt;head>
+ &lt;title>
+ &lt;xsl:value-of select="title"/>
+ &lt;/title>
+ &lt;/head>
+ &lt;body>
+ &lt;xsl:apply-templates/>
+ &lt;/body>
+ &lt;/html>
+ &lt;/xsl:template>
+
+ &lt;xsl:template match="doc/title">
+ &lt;h1>
+ &lt;xsl:apply-templates/>
+ &lt;/h1>
+ &lt;/xsl:template>
+
+ &lt;xsl:template match="chapter/title">
+ &lt;h2>
+ &lt;xsl:apply-templates/>
+ &lt;/h2>
+ &lt;/xsl:template>
+
+ &lt;xsl:template match="section/title">
+ &lt;h3>
+ &lt;xsl:apply-templates/>
+ &lt;/h3>
+ &lt;/xsl:template>
+
+ &lt;xsl:template match="para">
+ &lt;p>
+ &lt;xsl:apply-templates/>
+ &lt;/p>
+ &lt;/xsl:template>
+
+ &lt;xsl:template match="note">
+ &lt;p class="note">
+ &lt;b>NOTE: &lt;/b>
+ &lt;xsl:apply-templates/>
+ &lt;/p>
+ &lt;/xsl:template>
+
+ &lt;xsl:template match="emph">
+ &lt;em>
+ &lt;xsl:apply-templates/>
+ &lt;/em>
+ &lt;/xsl:template>
+
+&lt;/xsl:stylesheet>
+
+ </code></pre></td></tr></table>
+ <hr />
+ <hr />
+ <h4>Example 4 Erlang version</h4>
+ <p>
+ Erlang transformation of previous example:
+ </p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+
+-include("xmerl.hrl").
+
+-import(xmerl_xs,
+ [ xslapply/2, value_of/1, select/2, built_in_rules/2 ]).
+
+doctype()->
+ "&lt;!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\"\
+ \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd \">".
+
+process_xml(Doc)->
+ template(Doc).
+
+template(E = #xmlElement{name='doc'})->
+ [ "&lt;\?xml version=\"1.0\" encoding=\"iso-8859-1\"\?>",
+ doctype(),
+ "&lt;html xmlns=\"http://www.w3.org/1999/xhtml\" >"
+ "&lt;head>"
+ "&lt;title>", value_of(select("title",E)), "&lt;/title>"
+ "&lt;/head>"
+ "&lt;body>",
+ xslapply( fun template/1, E),
+ "&lt;/body>"
+ "&lt;/html>" ];
+
+
+template(E = #xmlElement{ parents=[{'doc',_}|_], name='title'}) ->
+ ["&lt;h1>",
+ xslapply( fun template/1, E),
+ "&lt;/h1>"];
+
+template(E = #xmlElement{ parents=[{'chapter',_}|_], name='title'}) ->
+ ["&lt;h2>",
+ xslapply( fun template/1, E),
+ "&lt;/h2>"];
+
+template(E = #xmlElement{ parents=[{'section',_}|_], name='title'}) ->
+ ["&lt;h3>",
+ xslapply( fun template/1, E),
+ "&lt;/h3>"];
+
+template(E = #xmlElement{ name='para'}) ->
+ ["&lt;p>", xslapply( fun template/1, E), "&lt;/p>"];
+
+template(E = #xmlElement{ name='note'}) ->
+ ["&lt;p class=\"note\">"
+ "&lt;b>NOTE: &lt;/b>",
+ xslapply( fun template/1, E),
+ "&lt;/p>"];
+
+template(E = #xmlElement{ name='emph'}) ->
+ ["&lt;em>", xslapply( fun template/1, E), "&lt;/em>"];
+
+template(E)->
+ built_in_rules( fun template/1, E).
+
+ </code></pre></td></tr></table>
+ <p>
+ It is important to end with a call to
+ <tt>xmerl_xs:built_in_rules/2</tt>
+ if you want any text to be written in "push" transforms.
+ That are the ones using a lot <tt>xslapply( fun
+ template/1, E )</tt> instead of
+ <tt>value_of(select("xpath",E))</tt>,
+ which is pull...
+ </p>
+ <hr />
+<p>The largest example is the stylesheet to transform this document
+ from the Simplified Docbook XML format to xhtml. The source
+ file is <tt>sdocbook2xhtml.erl</tt>.
+</p>
+
+
+ <h3 id="sect_4.3">Tips and tricks</h3>
+
+ <h4 id="sect_4.3.1">for-each</h4>
+ <p>The function for-each is quite common in XSLT stylesheets.
+ It can often be rewritten and replaced by select/1. Since
+ select/1 returns a list of #xmlElements and xslapply/2
+ traverses them it is more or less the same as to loop over all
+ the elements.
+ </p>
+
+
+ <h4 id="sect_4.3.2">position()</h4>
+ <p>The XSLT position() and #xmlElement.pos are not the
+ same. One has to make an own position in Erlang.</p>
+ <hr />
+ <h4>Example 5 Counting positions</h4>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+&lt;xsl:template match="stanza">
+ &lt;p>&lt;xsl:apply-templates select="line" />&lt;/p>
+&lt;/xsl:template>
+
+&lt;xsl:template match="line">
+ &lt;xsl:if test="position() mod 2 = 0">&amp;#160;&amp;#160;&lt;/xsl:if>
+ &lt;xsl:value-of select="." />&lt;br />
+&lt;/xsl:template>
+
+ </code></pre></td></tr></table>
+<p>Can be written as</p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+template(E = #xmlElement{name='stanza'}) ->
+ {Lines,LineNo} = lists:mapfoldl(fun template_pos/2, 1, select("line", E)),
+ ["&lt;p>", Lines, "&lt;/p>"].
+
+template_pos(E = #xmlElement{name='line'}, P) ->
+ {[indent_line(P rem 2), value_of(E#xmlElement.content), "&lt;br />"], P + 1 }.
+
+indent_line(0)->"&amp;#160;&amp;#160;";
+indent_line(_)->"".
+
+ </code></pre></td></tr></table>
+ <hr />
+
+
+ <h4 id="sect_4.3.3">Global tree awareness</h4>
+ <p>In XSLT you have "root" access to the top of the tree
+ with XPath, even though you are somewhere deep in your
+ tree.</p>
+ <p>The xslapply/2 function only carries back the child part
+ of the tree to the template fun. But it is quite easy to write
+ template funs that handles both the child and top tree.</p>
+ <hr />
+ <h4>Example 6 Passing the root tree</h4>
+ <p>The following example piece will prepend the article
+ title to any section title</p>
+ <table border="1" cellspacing="0" cellpadding="5" width="100%"
+bgcolor="#CCCCCC"><tr><td><pre><code>
+
+template(E = #xmlElement{name='title'}, ETop ) ->
+ ["&lt;h3>", value_of(select("title", ETop))," - ",
+ xslapply( fun(A) -> template(A, ETop) end, E),
+ "&lt;/h3>"];
+
+ </code></pre></td></tr></table>
+ <hr />
+ </body></html> \ No newline at end of file