XML/XPath

From Rosetta Code
Task
XML/XPath
You are encouraged to solve this task according to the task description, using any language you may know.

Perform the following three XPath queries on the XML Document below:

  • Retrieve the first "item" element
  • Perform an action on each "price" element (print it out)
  • Get an array of all the "name" elements

XML Document: 

<inventory title="OmniCorp Store #45x10^3">
  

    <item upc="123456789" stock="12">
      <name>Invisibility Cream</name>
      <price>14.50</price>
      <description>Makes you invisible</description>
    </item>
    <item upc="445322344" stock="18">
      <name>Levitation Salve</name>
      <price>23.99</price>
      <description>Levitate yourself for up to 3 hours per application</description>
    </item>
  

  

    <item upc="485672034" stock="653">
      <name>Blork and Freen Instameal</name>
      <price>4.95</price>
      <description>A tasty meal in a tablet; just add water</description>
    </item>
    <item upc="132957764" stock="44">
      <name>Grob winglets</name>
      <price>3.56</price>
      <description>Tender winglets of Grob. Just add water</description>
    </item>
  

</inventory>

C#

<lang csharp> XmlReader XReader; 

 // Either read the xml from a string ...
 XReader = XmlReader.Create(new StringReader("<inventory title=... </inventory>"));

 // ... or read it from the file system.
 XReader = XmlReader.Create("xmlfile.xml");

 // Create a XPathDocument object (which implements the IXPathNavigable interface)
 // which is optimized for XPath operation. (very fast).
 IXPathNavigable XDocument = new XPathDocument(XReader);

 // Create a Navigator to navigate through the document.
 XPathNavigator Nav = XDocument.CreateNavigator();
 Nav = Nav.SelectSingleNode("//item");

 // Move to the first element of the selection. (if available).
 if(Nav.MoveToFirst())
 {
   Console.WriteLine(Nav.OuterXml); // The outer xml of the first item element.
 }

 // Get an iterator to loop over multiple selected nodes.
 XPathNodeIterator Iterator = XDocument.CreateNavigator().Select("//price");

 while (Iterator.MoveNext())
 {
   Console.WriteLine(Iterator.Current.Value);
 }

 Iterator = XDocument.CreateNavigator().Select("//name");

 // Use a generic list.
 List<string> NodesValues = new List<string>();

 while (Iterator.MoveNext())
 {
   NodesValues.Add(Iterator.Current.Value);
 }

 // Convert the generic list to an array and output the count of items.
 Console.WriteLine(NodesValues.ToArray().Length);</lang>

ColdFusion

 <cfsavecontent variable="xmlString">
 <inventory
 ...
 </inventory>
 </cfsavecontent>
 <cfset xml = xmlParse(xmlString)>
 <!--- First Task --->
 <cfset itemSearch = xmlSearch(xml, "//item")>
 <!--- item = the first Item (xml element object) --->
 <cfset item = itemSearch[1]>
 <!--- Second Task --->
 <cfset priceSearch = xmlSearch(xml, "//price")>
 <!--- loop and print each price --->
 <cfloop from="1" to="#arrayLen(priceSearch)#" index="i">
   #priceSearch[i].xmlText#<br/>
 </cfloop>
 <!--- Third Task --->
 <!--- array of all the name elements --->
 <cfset names = xmlSearch(xml, "//name")>
 <!--- visualize the results --->
 <cfdump var="#variables#">

Groovy

def inventory = new XmlSlurper().parseText("<inventory...")    //optionally parseText(new File("inv.xml").text)
def firstItem = inventory.section.item[0]                      //1. first item
inventory.section.item.price.each { println it }               //2. print each price
def allNamesArray = inventory.section.item.name.collect {it}   //3. collect item names into an array

JavaScript

Works with: Firefox version 2.0

<lang javascript> //create XMLDocument object from file 

var xhr = new XMLHttpRequest();
xhr.open('GET', 'file.xml', false);
xhr.send(null);
var doc = xhr.responseXML;

//get first <item> element
var firstItem = doc.evaluate( '//item[1]', doc, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null ).singleNodeValue;
alert( firstItem.textContent );

//output contents of <price> elements
var prices = doc.evaluate( '//price', doc, null, XPathResult.ANY_TYPE, null );
for( var price = prices.iterateNext(); price != null; price = prices.iterateNext() ) {
  alert( price.textContent );
}

//add <name> elements to array
var names = doc.evaluate( '//name', doc, null, XPathResult.ANY_TYPE, null);
var namesArray = [];
for( var name = names.iterateNext(); name != null; name = names.iterateNext() ) {
  namesArray.push( name );
}
alert( namesArray );</lang>

Although some browsers support XPath, working with XML is much easier with E4X.

<lang javascript> //create XML object from file 

var xhr = new XMLHttpRequest();
xhr.open('GET', 'file.xml', false);
xhr.send(null);
var doc = new XML(xhr.responseText);

//get first <item> element
var firstItem = doc..item[0];
alert( firstItem );

//output contents of <price> elements
for each( var price in doc..price ) {
  alert( price );
}

//add <name> elements to array
var names = [];
for each( var name in doc..name ) {
  names.push( name );
}
alert( names );</lang>

Perl

Library: XML::XPathXPath
use XML::XPath qw();

my $x = XML::XPath->new('<inventory ... </inventory>');

[$x->findnodes('//item[1]')->get_nodelist]->[0];
print $x->findnodes_as_string('//price');
$x->findnodes('//name')->get_nodelist;

PHP

<lang php> 

 <?php
 //PHP5 only example due to changes in XML extensions between version 4 and 5 (Tested on PHP5.2.0)
 $doc = DOMDocument::loadXML('<inventory title="OmniCorp Store #45x10^3">...</inventory>');
 //Load from file instead with $doc = DOMDocument::load('filename');
 $xpath = new DOMXPath($doc);
 /* 
     1st Task: Retrieve the first "item" element
 */
 $nodelist = $xpath->query('//item');
 $result = $nodelist->item(0);
 /* 
     2nd task: Perform an action on each "price" element (print it out)
 */
 $nodelist = $xpath->query('//price');
 for($i = 0; $i < $nodelist->length; $i++)
 {
   //print each price element in the DOMNodeList instance, $nodelist, as text/xml followed by a newline
   print $doc->saveXML($nodelist->item($i))."\n";
 }
 /* 
     3rd Task: Get an array of all the "name" elements
 */
 $nodelist = $xpath->query('//name');
 //our array to hold all the name elements, though in practice you'd probably not need to do this and simply use the DOMNodeList
 $result = array(); 
 //a different way of iterating through the DOMNodeList
 foreach($nodelist as $node)
 {
   $result[] = $node; 
 }

</lang>

Python

<lang python>

  1. Python has basic xml parsing built in

from xml.dom import minidom

xmlfile = file("test3.xml") # load xml document from file xmldoc = xmldom.parse(xmlfile).documentElement # parse from file stream or... xmldoc = xmldom.parseString("<inventory title="OmniCorp Store #45x10^3">...</inventory>").documentElement # alternatively, parse a string

  1. 1st Task: Retrieve the first "item" element

i = xmldoc.getElementsByTagName("item") # get a list of all "item" tags firstItemElement = i[0] # get the first element

  1. 2nd task: Perform an action on each "price" element (print it out)

for j in xmldoc.getElementsByTagName("price"): # get a list of all "price" tags print j.childNodes[0].data # XML Element . TextNode . data of textnode

  1. 3rd Task: Get an array of all the "name" elements

namesArray = xmldoc.getElementsByTagName("name") </lang>

Ruby

 #Example taken from the REXML tutorial (http://www.germane-software.com/software/rexml/docs/tutorial.html)
 require "rexml/document"
 include REXML
 #create the REXML Document from the string (%q is Ruby's multiline string, everything between the two @-characters is the string)
 doc = Document.new(
         %q@<inventory title="OmniCorp Store #45x10^3">
              ...
            </inventory>
           @
                           )
 # The invisibility cream is the first <item>
 invisibility = XPath.first( doc, "//item" ) 
 # Prints out all of the prices
 XPath.each( doc, "//price") { |element| puts element.text }
 # Gets an array of all of the "name" elements in the document.
 names = XPath.match( doc, "//name" )

Tcl

Using tDOM <lang tcl># assume $xml holds the XML data package require tdom set doc [dom parse $xml] set root [$doc documentElement]

set allNames [$root selectNodes //name] puts [llength $allNames] ;# ==> 4

set firstItem [lindex [$root selectNodes //item] 0] puts [$firstItem @upc] ;# ==> 123456789

foreach node [$root selectNodes //price] { 

   puts [$node text]

}</lang>

Visual Basic .NET

       Dim first_item = xml.XPathSelectElement("//item")
       Console.WriteLine(first_item)

       For Each price In xml.XPathSelectElements("//price")
           Console.WriteLine(price.Value)
       Next

       Dim names = (From item In xml.XPathSelectElements("//name") Select item.Value).ToArray


XSLT

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="text" />
  <xsl:template match="/">
  
    <!-- 1. first item element -->
    <xsl:text>
The first item element is</xsl:text>
    <xsl:value-of select="//item[1]" />
    
    <!-- 2. Print each price element -->
    <xsl:text>
The prices are: </xsl:text>
    <xsl:for-each select="//price">
      <xsl:text>
      </xsl:text>
      <xsl:copy-of select="." />
    </xsl:for-each>
    
    <!-- 3. Collect all the name elements -->
    <xsl:text>
The names are: </xsl:text>
    <xsl:copy-of select="//name" />
  </xsl:template>  
</xsl:stylesheet>
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