Accessing XML using E4X

OpenAf uses the Java Mozilla Rhino javascript engine and one of the features that, despite being obsolete, has still been kept is E4X.

E4X simply allows for easy interaction of XML content in Javascript.

Let’s start by the following XML example:

<shopcart>
  <!-- Client id -->
  <client type="personal" id="12345">
    <name>Joe Smith</name>
  </client>

  <!-- Store id -->
  <store>
    <id>12345</id>
    <type>diy</type>
  </store>

  <!-- Items on the shopcart -->
  <items>
    <item id="123">
       <qty>1</qty>
       <name>Item 1</name>
    </item>
    <item id="456">
       <qty>10</qty>
       <name>Item 2</name>
    </item>
  </items>
</shopcart>

Loading XML to OpenAF

You can load this xml from a file:

var xml = io.readFileXML("myxml.xml");

From a string:

var xml = new XMLList(myXMLString);

Or directly:

var xml = <shopcart><!-- Client id --><client type="personal" id="12345">...

All of them will result in a xml javascript variable of type “xml”.

Accessing data using the xml variable in javascript

To access any element simply think like you would access it if it was a JSON map:

> xml.client.name.toString()
"Joe Smith"
> xml.store.id.toString()
"12345"

Each element has several methods from which we are using the toString method. There is a list of methods on the end of this section.

For attributes it’s the same but add the prefix ”@”:

> xml.client.@type.toString()
"personal"

For multiple items you can think of it now as an array:

> xml.items.item[0].@id.toString()
123
> xml.items.item[1].qty.toString()
10

But this, is also valid (think of it as the first “store” tag element):

> xml.store[0].id.toString()
"12345"

Accessing all children nodes

> xml.children()[1].name.toString()
"Joe Smith"

Why is the children element on position 1 and not in 0? Because comments are also nodes:

> xml.children()[0].toString()
"<!-- Client id -->"

Using for cycles

Don’t forget that you are in javascript, so you can do for cycles:

var totalQty = 0;
for(var i in xml.items.item) {
    totalQty += Number(xml.items.item[i].qty);
}
// 11

You can also search all descendants in a for cycle:

for(var i in xml..name) {
    print(xml..name[i].toString());
}
// Joe Smith
// Item 1
// Item 2

Using namespaces

You can also use namespaces:

var xml = <links><a xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.google.com">Test link</a></links>;

var ns = new Namespace("http://www.w3.org/1999/xlink");
var url = xml..a;
var link = url.@ns::href;
// http://www.google.com

XML Object methods

Method	Description
attribute(attributeName)	Returns the attribute attributeName from the corresponding XML element node.
attributes()	Returns a list of the attributes associated with the corresponding XML element node.
child(propertyName)	Returns the children elements named propertyName associated with the corresponding XML element node.
children()	Returns all children elements associated with the corresponding XML element node.
descendants(name)	Equivalent to “xml..name”.
elements(name)	Equivalent to children() if no name is provided or equivalent to child if a name is provided.
parent()	Returns the parent element associated with the corresponding XML element node.
comments()	Returns the children elements of type ‘comment’ associated with the corresponding XML element node.
text()	Returns the text component of the corresponding XML element node.
name()	Returns a map with the name and local name associated with the corresponding XML element node.
localName()	Returns the local name associated with the corresponding XML element node.
namespace(prefix)	Returns the namespace for the provided prefix of the namespace associated with the corresponding XML element node.
namespaceDeclarations()	Returns an array of namespaces associated with the corresponding XML element node.
childIndex()	Returns the index number on the childrens list of the corresponding XML element node.
length()	Returns the size of the children elements of the corresponding XML element node.
nodeKind()	Returns if the corresponding XML element node is a element of a comment.
toString()	Returns the string of the current XML element node.
toXMLString()	Returns the XML encoded string of the current XML element node.