Developing ColdFusion MX Applications with CFML
Using XML and WDDX

The XML document object

ColdFusion represents an XML document as an object, called an XML document object, that is much like a standard ColdFusion structure. In fact, most ColdFusion structure functions, such as StructInsert, work with XML document objects. For a full list of ColdFusion functions that work on XML document objects, see "Functions for XML object management".

You can look at the overall structure of an XML document in two ways: a basic view and a DOM (Document Object Model)-based node view. The basic view presents all the information in the document, but does not separate the data into as fine-grained units as the node view. ColdFusion can access XML document contents using either view.

A simple XML document

The next sections describe the basic and node views of the following simple XML document. This document is used in many of the examples in this chapter.

<?xml version="1.0" encoding="UTF-8"?>

<employee>
<!-- A list of employees -->
 <name EmpType="Regular">
  <first>Almanzo</first>
  <last>Wilder</last>
 </name>
 <name EmpType="Contract">
  <first>Laura</first>
  <last>Ingalls</last>
 </name>
</employee>

Basic view

The basic view of an XML document object presents the object as a container that holds one root element structure. The root element can have any number of nested element structures. Each element structure represents an XML tag (start tag/end tag set) and all its contents; it can contain additional element structures. A basic view of the simple XML document looks like the following:

DOM node view

The DOM node view presents the XML document object using the same format as the document's XML Document Object Model (DOM). In fact, an XML document object is a representation of a DOM object.

The DOM is a World Wide Web Consortium (W3C) recommendation (specification) for a platform- and language-neutral interface to dynamically access and update the content, structure, and style of documents. ColdFusion conforms to the DOM Level 2 Core specification, available at http://www.w3.org/TR/DOM-Level-2-Core.

In the DOM node view, the document consists of a hierarchical tree of nodes. Each node has a DOM node type, a node name, and a node value. Node types include Element, Comment, Text, and so on. The DOM structures the document object and each of the elements it contains into multiple nodes of different types, providing a finer-grained view of the document structure than the basic view. For example, if an XML comment is in the middle of a block of text, the DOM node view represents its position in the text while the basic view does not.

ColdFusion also allows you to use the DOM objects, methods, and properties defined in the W3C DOM Level 2 Core specification to manipulate the XML document object.

For more information on referencing DOM nodes, see "XML DOM node structure". This document does not cover the node view and using DOM methods and properties in detail.

XML document structures

An XML document object is a structure that contains a set of nested XML element structures. The following figure shows the output of a cfdump tag that displays the document object for the XML in "A simple XML document". The following figure shows the output of the cfdump tag:

The following code displays this output. It assumes that you save the code in a file under your web root, such as C:\Inetpub\wwwroot\testdocs\employeesimple.xml

<cffile action="read" file="C:\Inetpub\wwwroot\testdocs\employeesimple.xml"
variable="xmldoc">

<cfset mydoc = XmlParse(xmldoc)>
<cfdump var="#mydoc#">

The document object structure

At the top level, the XML document object has the following three entries:

Entry name	Type	Description
XmlRoot	Element	The root element of the document.
XmlComment	String	A string made of the concatenation of all comments on the document, that is, comments in the document prologue and epilog. This string does not include comments inside document elements.
XmlDocType	XmlNode	The DocType attribute of the document. This entry only exists if the document specifies a DocType. This entry does not appear when cfdump displays an XML element structure.

The element structure

Each XML element has the following entries:

Entry name	Type	Description
XmlName	String	The name of the element.
XmlNsPrefix	String	The prefix of the Namespace.
XmlNsURI	String	The URI of the Namespace.
XmlText	String	A string made of the concatenation of all text and CData text in the element, but not inside any child elements.
XmlComment	String	A string made of the concatenation of all comments inside the XML element, but not inside any child elements.
XmlAttributes	Structure	All of this element's attributes, as name-value pairs.
XmlChildren	Array	All this element's children elements.
XmlParent	XmlNode	The parent DOM node of this element. This entry does not appear when cfdump displays an XML element structure.
XmlNodes	Array	An array of all the XmlNode DOM nodes contained in this element. This entry does not appear when cfdump displays an XML element structure.

XML DOM node structure

The following table lists the contents of an XML DOM node structure:

Entry name	Type	Description
XmlName	String	The node name. For nodes such as Element or Attribute, the node name is the element or attribute name.
XmlType	String	The node XML DOM type, such as Element or Text.
XmlValue	String	The node value. This entry is used only for Attribute, CDATA, Comment, and Text type nodes.

Note:   The cfdump tag does not display XmlNode structures. If you try to dump an XmlNode structure, the cfdump tag displays "Empty Structure".

The following table lists the contents of the XmlName and XmlValue fields for each node type that is valid in the XmlType entry. The node types correspond to the objects types in the XML DOM hierarchy.

Node type	XmlName	xmlValue
CDATA	#cdata-section	Content of the CDATA section
COMMENT	#comment	Content of the comment
ELEMENT	Tag name	Empty string
ENTITYREF	Name of entity referenced	Empty string
PI (processing instruction)	Target entire content excluding the target	Empty string
TEXT	#text	Content of the text node
ENTITY	Entity name	Empty string
NOTATION	Notation name	Empty string
DOCUMENT	#document	Empty string
FRAGMENT	#document-fragment	Empty string
DOCTYPE	Document type name	Empty string

Note:   Although XML attributes are nodes on the DOM tree, ColdFusion does not expose them as XML DOM node data structures. To view an element's attributes, use the element structure's XMLAttributes structure.

The XML document object and all its elements are exposed as DOM node structures. For example, you can use the following variable names to reference nodes in the DOM tree created from the XML example in "A simple XML document":

mydoc.XmlName

mydoc.XmlValue
mydoc.XmlRoot.XmlName
mydoc.employee.XmlType
mydoc.employee.XmlNodes[1].XmlType

Copyright © 2002, Macromedia Inc. All rights reserved.

Comments