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class Xml

Overview

Parsing DOM

Build a DOM tree using Xml.parseFile() or Xml.parseString(). To read the file, do the following.

var doc = Xml.parseFile("xmlfile.xml");

The following is an example of directly parsing a string.

var doc = Xml.parseString(%{
<?xml version="1.0" encoding="UTF-8" ?>
<artists>
  <product country="US" id="1">
    <name>Power Snack</name>
    <price>2400</price>
    <img file="powersnack.jpg"/>
  </product>
  <product country="US" id="2">
    <name>Babystar Icecream</name>
    <price>21000</price>
    <img file="babystar.jpg"/>
  </product>
  <product country="DE" id="3">
    <name>Panic! Panic! Panic!</name>
    <price>2400</price>
    <img file="panic.jpg"/>
  </product>
</artists>
});

The returned document object has the following methods.

Method Content
documentElement() Gets the root document
createElement(tagname) Creates an Element node
createTextNode(text) Creates a Text node
createComment(comment) Creates a Comment node
createCdataSection(content) Creates a CDATA Section node
createProcessingInstruction(target, data) Creates a Processing Instruction node
createEntityReference(name) Creates an Entity Reference node
createElementNS(nsUri, qname) Creates an Element node by specifying the namespace
getElementById(id) Search for a node by specifying id
getElementsByTagName(tagName) Returns the node of tagName as an array
xpath(expr) Evaluates the XPATH of expr and returns the result as an array

Root node

The root node is obtained using the documentElement() method as follows.

var root = doc.documentElement();

XML node

XML nodes, including the root node, have the following properties and methods.

Properties
Properties Content
type Node type
name QName
tagName Tag name
localName Local name
namespaceURI Namespace URI
prefix Prefix

Methods

Method Content
attributes() Returns an attribute list as an array.
setAttribute(qname, value) Set the attribute.
setAttributeNS(nsUri, qname, value) Set the attribute by specifying the namespace.
removeAttribute(qname) Removes an attribute.
removeAttributeNS(nsUri, localName) Removes the attribute by specifying the namespace.
getAttribute(qname) Get the attribute.
getAttributeNS(nsUri, qname) Get the attribute by specifying the namespace.
parentNode() Returns the parent node.
children() Returns the child nodes as an array.
firstChild() Returns the first child node.
lastChild() Returns the last child node.
nextSibling() Returns the next node.
previousSibling() Returns the previous node.
appendChild(node) Adds a node to the child node.
removeChild(node) Removes a node from child nodes.
replaceChild(node1, node2) Replaces the child node.
replaceNode(node) Replaces one's own node with another node.
insertBefore(node) Add a node as the previous node.
insertAfter(node) Add a node as the next node.
remove() Removes the node.
textContent() Gets the text.
innerText() Gets the text.
hasChildren() Returns 1 if a child node exists.
hasAttributes() Returns 1 if there are attributes.
getElementById(id) Search for a node by specifying id
getElementsByTagName(tagName) Returns the node of tagName as an array
xpath(expr) Evaluates the XPATH of expr and returns the result as an array

XPath

XPath returns the nodes that match the XPATH expression in the form of a node set (array). The node set also has an xpath() method, and you can use it by chaining XPATH to the narrowed down nodes.

Run the following with the sample XML document above.

var nodes = doc.xpath("//product")
               .xpath("price")
               .map(&(p) => p.innerText());

nodes.each(&(text) => {
    System.println(text);
});

Result.

2400
21000
2400

By the way, using a block syntax and a numbered parameter supported recently, you can also write the following.

var nodes = doc.xpath("//product")
               .xpath("price")
               .map { => _1.innerText() };

nodes.each {
    System.println(_1);
};

Examples

Example 1. Parsing Xml

Code

function displayXml(doc, node, indent) {
    System.print("  " * indent);
    if (node.type == Xml.ELEMENT_NODE) {
        System.print("ELEM %s" % node.name);
    } else if (node.type == Xml.TEXT_NODE) {
        System.print("TEXT %s" % node.value.trim());
    }

    var attr = node.attributes();
    for (var i = 0, len = attr.length(); i < len; ++i) {
        System.print("[%s=%s]" % attr[i].name % attr[i].value);
    }
    System.println("");

    var child = node.firstChild();
    while (child) {
        displayXml(doc, child, indent + 1);
        child = child.nextSibling();
    }
}

var doc = Xml.parseString(%{
<?xml version="1.0" encoding="UTF-8" ?>
<artists>
  <product country="US" id="1">
    <name>Power Snack</name>
    <price>2400</price>
    <img file="powersnack.jpg"/>
  </product>
  <product country="US" id="2">
    <name>Babystar Icecream</name>
    <price>21000</price>
    <img file="babystar.jpg"/>
  </product>
  <product country="DE" id="3">
    <name>Panic! Panic! Panic!</name>
    <price>2400</price>
    <img file="panic.jpg"/>
  </product>
</artists>
});

var root = doc.documentElement();
displayXml(doc, root);

Result

ELEM artists
  TEXT
  ELEM product[country=US][id=1]
    TEXT
    ELEM name
      TEXT Power Snack
    TEXT
    ELEM price
      TEXT 2400
    TEXT
    ELEM img[file=powersnack.jpg]
    TEXT
  TEXT
  ELEM product[country=US][id=2]
    TEXT
    ELEM name
      TEXT Babystar Icecream
    TEXT
    ELEM price
      TEXT 21000
    TEXT
    ELEM img[file=babystar.jpg]
    TEXT
  TEXT
  ELEM product[country=DE][id=3]
    TEXT
    ELEM name
      TEXT Panic! Panic! Panic!
    TEXT
    ELEM price
      TEXT 2400
    TEXT
    ELEM img[file=panic.jpg]
    TEXT
  TEXT

Example 2. DOM methods

Code

function displayXml(doc, node, indent) {
    System.print("  " * indent);
    if (node.type == Xml.ELEMENT_NODE) {
        System.print("ELEM %s" % node.name);
    } else if (node.type == Xml.TEXT_NODE) {
        System.print("TEXT %s" % node.value.trim());
    }

    var attr = node.attributes();
    for (var i = 0, len = attr.length(); i < len; ++i) {
        System.print("[%s=%s]" % attr[i].name % attr[i].value);
    }
    System.println("");

    var child = node.firstChild();
    while (child) {
        displayXml(doc, child, indent + 1);
        child = child.nextSibling();
    }
}

var doc = Xml.parseString(%{
<?xml version="1.0" encoding="UTF-8" ?>
<artists>
  <product country="US" id="1">
    <name>Power Snack</name>
    <price>2400</price>
    <img file="powersnack.jpg"/>
  </product>
  <product country="US" id="2">
    <name>Babystar Icecream</name>
    <price>21000</price>
    <img file="babystar.jpg"/>
  </product>
  <product country="DE" id="3">
    <name>Panic! Panic! Panic!</name>
    <price>2400</price>
    <img file="panic.jpg"/>
  </product>
</artists>
});

var root = doc.documentElement();
var el = root.getElementById("3");
if (el) {
    el.remove();
}

System.println("getElementByTagName:");
var els = root.getElementsByTagName("img");
if (els.isArray) {
    els.each(&(el) => displayXml(doc, el));
}

Result

getElementByTagName:
ELEM img[file=powersnack.jpg]
ELEM img[file=babystar.jpg]

Example 3. XPath

Code

function displayXml(doc, node, indent) {
    System.print("  " * indent);
    if (node.type == Xml.ELEMENT_NODE) {
        System.print("ELEM %s" % node.name);
    } else if (node.type == Xml.TEXT_NODE) {
        System.print("TEXT %s" % node.value.trim());
    }

    var attr = node.attributes();
    for (var i = 0, len = attr.length(); i < len; ++i) {
        System.print("[%s=%s]" % attr[i].name % attr[i].value);
    }
    System.println("");

    var child = node.firstChild();
    while (child) {
        displayXml(doc, child, indent + 1);
        child = child.nextSibling();
    }
}

var doc = Xml.parseString(%{
<?xml version="1.0" encoding="UTF-8" ?>
<artists>
  <product country="US" id="1">
    <name>Power Snack</name>
    <price>2400</price>
    <img file="powersnack.jpg"/>
  </product>
  <product country="US" id="2">
    <name>Babystar Icecream</name>
    <price>21000</price>
    <img file="babystar.jpg"/>
  </product>
  <product country="DE" id="3">
    <name>Panic! Panic! Panic!</name>
    <price>2400</price>
    <img file="panic.jpg"/>
  </product>
</artists>
});

var root = doc.documentElement();
var el = root.getElementById("3");
if (el) {
    el.remove();
}

System.println("XPath:");
var nodes = doc.xpath("//product").xpath("price");
if (nodes.isArray) {
    nodes.each(&(el) => displayXml(doc, el));
}

Result

XPath:
ELEM price
  TEXT 2400
ELEM price
  TEXT 21000

Example 4. XmlWriter

Code

I introduce the sample source included in the repo. There is Xml.Writer which is not explained, but it will be helpful for displaying DOM.

var doc = Xml.parseString(%{
<?xml version="1.0" encoding="UTF-8" ?>
<artists>
  <product country="US" id="1">
    <name>Power Snack</name>
    <price>2400</price>
    <img file="powersnack.jpg"/>
  </product>
  <product country="US" id="2">
    <name>Babystar Icecream</name>
    <price>21000</price>
    <img file="babystar.jpg"/>
  </product>
  <product country="DE" id="3">
    <name>Panic! Panic! Panic!</name>
    <price>2400</price>
    <img file="panic.jpg"/>
  </product>
</artists>
});

var root = doc.documentElement();
var el = root.getElementById("3");
if (el) {
    el.remove();
}

var xmlWriter = new Xml.Writer(System, { tab: "        " });
xmlWriter.write(doc);
xmlWriter.write(root);

Result

<artists>
        <product country="US" id="1">
                <name>Power Snack</name>
                <price>2400</price>
                <img file="powersnack.jpg" />
        </product>
        <product country="US" id="2">
                <name>Babystar Icecream</name>
                <price>21000</price>
                <img file="babystar.jpg" />
        </product>
</artists>
<artists>
        <product country="US" id="1">
                <name>Power Snack</name>
                <price>2400</price>
                <img file="powersnack.jpg" />
        </product>
        <product country="US" id="2">
                <name>Babystar Icecream</name>
                <price>21000</price>
                <img file="babystar.jpg" />
        </product>
</artists>