Accessing the Document Tree
You can access the tree for an XML document either by beginning at the root element and moving from node to node or by querying for a specific node or nodes. You can navigate to the root element of the document by using the documentElement
property. This property returns the root element as an IXMLDOMNode
.
The following books.xml file is the same as the file used in the document map.
<?xml version="1.0" encoding="UTF-8"?> <?xml-stylesheet type="text/xsl" href="show_book.xsl"?> <!DOCTYPE catalog SYSTEM "catalog.dtd"> <!--catalog last updated 2000-11-01--> <catalog xmlns="http://www.example.com/catalog/"> <book id="bk101"> <author>Gambardella, Matthew</author> <title>XML Developer's Guide</title> <genre>Computer</genre> <price>44.95</price> <publish_date>2000-10-01</publish_date> <description><![CDATA[An in-depth look at creating applications with XML, using <, >,]]> and &.</description> </book> <book id="bk109"> <author>Kress, Peter</author> <title>Paradox Lost</title> <genre>Science Fiction</genre> <price>6.95</price> <publish_date>2000-11-02</publish_date> <description>After an inadvertant trip through a Heisenberg Uncertainty Device, James Salway discovers the problems of being quantum.</description> </book> </catalog>
You can walk the tree to the first level of elements contained by the root using Microsoft® Visual Basic® Scripting Edition (VBScript).
Dim root Dim xmlDoc Dim child Set xmlDoc = CreateObject("Msxml2.DOMDocument.5.0") xmlDoc.async = False xmlDoc.load("c:\books.xml") If (xmlDoc.parseError.errorCode <> 0) Then Dim myErr Set myErr = xmlDoc.parseError MsgBox("You have error " & myErr.reason) Else 'Set root to the XML document's root element, COLLECTION: Set root = xmlDoc.documentElement 'Walk from the root to each of its child nodes: For Each child In root.childNodes MsgBox child.text Next End If
When run, this example displays the text of each of the root's child nodes (book elements) as a separate text message.
You can use the following methods to navigate to a specific node or nodes deep within the tree.
- nodeFromID method
The
nodeFromID
method takes a unique ID, as identified by an XML schema or document type definition (DTD), and returns the node corresponding to that specific ID. - getElementsByTagName method (DOMDocument)
The
getElementsByTagName
method takes a string representing a specific tag name and returns all element nodes with this tag name.
You can use the following code to retrieve all element nodes named <AUTHOR>
in books.xml.
Dim ElemList Dim xmlDoc Set xmlDoc = CreateObject("Msxml2.DOMDocument.5.0") xmlDoc.async = False xmlDoc.load("c:\xml\books.xml") If (xmlDoc.parseError.errorCode <> 0) Then Dim myErr Set myErr = xmlDoc.parseError MsgBox("You have error " & myErr.reason) Else Set ElemList = xmlDoc.getElementsByTagName("author") For i=0 To (ElemList.length -1) MsgBox ElemList.item(i).xml Next End If
The selectNodes
method of the IXMLDOMNode
object offers a more flexible way of accessing nodes using XML Path Language (XPath).
See Also
Document Map | documentElement Property | IXMLDOMNode | selectNodes Method