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* An example of using toXML to pass structured information to a

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builder and generate a Jetty configuration file with XSLT.
This commit is contained in:
Eelco Dolstra 2006-10-03 15:39:34 +00:00
parent 5fd44654db
commit 96fa456a0a
1 changed files with 76 additions and 3 deletions
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79
doc/manual/writing-nix-expressions.xml
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@ -1288,8 +1288,9 @@ command-line argument. See <xref linkend='sec-standard-environment'
<varlistentry><term><function>builtins.add</function>
<replaceable>e1</replaceable> <replaceable>e2</replaceable></term>
<listitem><para>Add integers <replaceable>e1</replaceable> and
<replaceable>e2</replaceable>..</para></listitem>
<listitem><para>Return the sum of the integers
<replaceable>e1</replaceable> and
<replaceable>e2</replaceable>.</para></listitem>
</varlistentry>
@ -1710,7 +1711,79 @@ in foo</programlisting>
of <replaceable>e</replaceable>. The main application for
<function>toXML</function> is to communicate information with the
builder in a more structured format than plain environment
variables.</para></listitem>
variables.</para>
<example xml:id='ex-toxml'><title>Passing information to a builder
using <function>toXML</function></title>
<programlisting>
<![CDATA[
{stdenv, fetchurl, libxslt, jira, uberwiki}:
stdenv.mkDerivation (rec {
name = "web-server";
buildInputs = [libxslt];
builder = builtins.toFile "builder.sh" "
source $stdenv/setup
mkdir $out
echo $servlets | xsltproc ${stylesheet} - > $out/server-conf.xml
";
stylesheet = builtins.toFile "stylesheet.xsl" "<?xml version='1.0' encoding='UTF-8'?>
<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
<xsl:template match='/'>
<Configure>
<xsl:for-each select='/expr/list/attrs'>
<Call name='addWebApplication'>
<Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
<Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
</Call>
</xsl:for-each>
</Configure>
</xsl:template>
</xsl:stylesheet>
";
servlets = builtins.toXML [
{ path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
{ path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
];
})]]></programlisting>
</example>
<para>The string in the attribute <varname>servlets</varname>
evaluates to something like this:
<programlisting>
<![CDATA[
<?xml version='1.0' encoding='utf-8'?>
<expr>
<list>
<attrs>
<attr name="path">
<string value="/bugtracker" />
</attr>
<attr name="war">
<path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
</attr>
</attrs>
<attrs>
<attr name="path">
<string value="/wiki" />
</attr>
<attr name="war">
<path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
</attr>
</attrs>
</list>
</expr>]]></programlisting>
</para>
</listitem>
</varlistentry>