Xml dom & sax by bhavsingh maloth

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Introduction
Introducing the DOM Objects

Working with the XML DOM
Validate and tranform an XML document

Exercises

Document Object Model

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Introducing the W3C DOM
 DOM Implementation



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

XML Document Object Model (DOM)

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◦ W3C standard recommendation
◦ Build tree structure in memory for XML documents
◦ Provides an Application Programming Interface (API) for
dynamically accessing and manipulating a document
◦ DOM-based parsers parse these structures
 Exist in several languages (Java, C, C++, Python, Perl, etc.)


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

Tree Structure of a Document:

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◦ Node is the basic building block of the DOM tree
structure.
◦ Nodes represent elements, attributes, content,
comments, etc.


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◦ Example
<?xml version = "1.0"?>
<message from = "Paul" to = "Tem">
<body>Hi, Tim!</body>
</message>

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 Node created for element message

 Element message has child node for body element
 Element body has child node for text "Hi, Tim!"
 Attributes from and to also have nodes in tree


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The following figure represents how a DOM tree is used by applications to access data:

MSXML Library or other libraries
XML
Document

Parser
Parsed
Document

DOM Tree
Root
Child

Application
Text

Child
Text


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

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DOM-based parsers
◦
◦
◦
◦
◦
◦
◦
◦
◦

Sun Microsystem’s JAXP
Apache Xerces
XML4J
DOM4J
JDOM
Microsoft’s msxml
4DOM
XML::DOM
…


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Class/Interface

Description

Document interface

Represents the XML document’s top-level node, which provides
access to all the document’s nodes—including the root element.

Node interface

Represents an XML document node.

NodeList interface

Represents a read-only list of Node objects.

Element interface

Represents an element node. Derives from Node.

Attr interface

Represents an attribute node. Derives from Node.

CharacterData interface Represents character data. Derives from Node.
Text interface
Represents a text node. Derives from CharacterData.
Comment interface

Represents a comment node. Derives from CharacterData.

ProcessingInstruction
interface
CDATASection interface

Represents a processing instruction node. Derives from Node.
Represents a CDATA section. Derives from Text.


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Method Name

Description

createElement

Creates an element node.

createAttribute

Creates an attribute node.

createTextNode

Creates a text node.

createComment

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Creates a comment node.

createProcessingInstruction Creates a processing instruction node.
createCDATASection
Creates a CDATA section node.
getDocumentElement

Returns the document’s root element.

appendChild

Appends a child node.

getChildNodes

Returns the child nodes.


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

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Following are the associated properties for the
S
Document object methods:
◦
◦
◦
◦
◦
◦

childNodes
documentElement
firstChild
lastChild
parseError
validateOnParse


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Method Name

Description

appendChild

Appends a child node.

cloneNode

Duplicates the node.

getAttributes Returns the node’s attributes.

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getChildNodes Returns the node’s child nodes.
getNodeName

Returns the node’s name.

getNodeType

Returns the node’s type (e.g., element, attribute,
text, etc.).

getNodeValue

Returns the node’s value.

getParentNode Returns the node’s parent.
hasChildNodes Returns true if the node has child nodes.
removeChild

Removes a child node from the node.

replaceChild

Replaces a child node with another node.

setNodeValue

Sets the node’s value.

insertBefore

Appends a child node in front of a child node.


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

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Following are the associated properties Sthe
for
Node object methods:
◦
◦
◦
◦
◦
◦
◦

nodeName
nodeType
nodeValue
childNodes
firstChild
lastChild
text


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Node Type

Description

Node.ELEMENT_NODE

Represents an element node.

Node.ATTRIBUTE_NODE

Represents an attribute node.

Node.TEXT_NODE

Represents a text node.

Node.COMMENT_NODE

Represents a comment node.

Node.PROCESSING_INSTRUCTION_NODE

Represents a processing instruction node.

Node.CDATA_SECTION_NODE

Represents a CDATA section node.


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Method Name

Description

getAttribute

Returns an attribute’s value.

getTagName

Returns an element’s name.

removeAttribute

Removes an element’s attribute.

setAttribute

Sets an attribute’s value.


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<?xml version="1.0"?>
<article>
<title>XML Demo</title>
<date>August 22, 2007</date>
<author>
<fname>Nguyen Van</fname>
<lname>Teo</lname>
</author>
<summary>XML is pretty easy.</summary>
<content>Once you have mastered HTML, XML is
easily
learned. You must remember that XML is not for
displaying information but for managing
information.
</content>
</article>


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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>A DOM Example</title>
</head>
<body>

Element script allows for
including scripting code

<script type = "text/javascript" language
"JavaScript">

Instantiate
Microsoft XML
=
DOM object

var xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.load("article.xml");
Load article.xml into memory;
var

msxml parses article.xml and
element=xmlDoc.documentElement; stores it as tree structure


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Assign article as root element
var element=xmlDoc.documentElement;// get the root element
document.writeln(
"Here is the root node of the document:" );
document.writeln( "" + element.nodeName
+ "" );

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Place root element’s name in element
strong and write it to browser

document.writeln(
" The following are its child elements:" );
document.writeln( "<ul>" );

// traverse all child nodes of root element
for ( i = 0; i < element.childNodes.length; i++ ) {
var curNode = element.childNodes.item(i);

}

// print node name of each child element
document.writeln( "<li>" + curNode.nodeName
+ "</li>" );

Assign index to each
child node of root node

document.writeln( "</ul>" );
// get the first child node of root element
var currentNode = element.firstChild;

Retrieve root node’s first
child node (title)

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Siblings are nodes at same level in

document.writeln( "The first child of root node is:" );
document (e.g., title, date,
document.writeln( "" + currentNode.nodeName
+ "" );
author, summary and content)
document.writeln( " whose next sibling is:" );
// get the next sibling of first child
var nextSib = currentNode.nextSibling;
document.writeln( "" + nextSib.nodeName
+ "." );
Get first child’s next sibling (date)
document.writeln( " Value of " + nextSib.nodeName
+ " element is:" );
var value = nextSib.firstChild;

Get first child of date

// print the text value of the sibling
document.writeln( "" + value.nodeValue + "" );
document.writeln( " Parent node of " );
document.writeln( "" + nextSib.nodeName
+ " is:" );
document.writeln( "" + nextSib.parentNode.nodeName
+ "." );
</script>
</body>
</html>

Get parent of date (article)


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Validate XML document with DTD
 Read XML document



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

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To be continued…


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XML How to program
 http://www.w3.org
 XML tutorial http://www.w3schools.com/w3c/



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Feel free to post questions at
http://yht4ever.blogspot.com
 or email to:
thanh.phamhong@niithoasen.com or
thanh.phamhong@niit-vn.com



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Xml dom & sax by bhavsingh maloth

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