6
XML
6.4 DOM
The XML Alphabet Soup
XML Extensible Markup Language Extensible Stylesheet Language XSL Transformations Defines XML documents
XSL
Language for expressing stylesheets; consists of XSLT and XSL-FO Language for transforming XML documents
XSLT
XSL-FO
XSL Formatting Objects
Language to describe precise layout of text on a page
Data Island Data Binding Namespace
XML data embedded in a HTML page Automatic population of HTML elements from XML data A collection of names, identified by a URI reference, which are used in XML documents
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
The XML Alphabet Soup
DTD DOM Document Type Definition Document Object Model Non-XML schema API to read, create and edit XML documents; creates in-memory object model API to parse XML documents; event-driven an XML based alternative to DTD
SAX XML Schema (XSD) XPath
Simple API for XML XML Schema Definition
XML Path Language
A language for addressing parts of an XML document, designed to be used by both XSLT and XPointer Supports addressing into the internal structures of XML documents Describes links between XML documents Flexible mechanism for querying XML data as if it were a database
XPointer XLink XQuery
XML Pointer Language XML Linking Language XML Query Language (draft)
The XML Alphabet Soup
SOAP Simple Object Access Protocol Web Services Description Language Wireless Application Protocol Wireless Markup Language A simple XML based protocol to let applications exchange information over HTTP An XML-based language for describing Web services and how to access them The leading standard for information services on wireless terminals like digital mobile phones WAP uses the mark-up language WML (not HTML)
WSDL WAP
WML
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
SAX and DOM
SAX and DOM are standards for XML parsers - program APIs to read and interpret XML files
DOM is a W3C standard SAX is an ad-hoc (but very popular) standard
There are various implementations available Java implementations are provided in JAXP (Java API for XML Processing) JAXP is included as a package in Java 1.4
JAXP is available separately for Java 1.3
Unlike many XML technologies, SAX and DOM are relatively easy
Difference between SAX and DOM
DOM reads the entire XML document into memory and stores it as a tree data structure SAX reads the XML document and sends an event for each element that it encounters Consequences:
DOM provides random access into the XML document SAX provides only sequential access to the XML document DOM is slow and requires huge amounts of memory, so it cannot be used for large XML documents SAX is fast and requires very little memory, so it can be used for huge documents (or large numbers of documents)
This makes SAX much more popular for web sites
Some DOM implementations have methods for changing the XML document in memory; SAX implementations do not
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
SAX Callbacks
SAX works through callbacks: you call the parser, it calls methods that you supply
Your program The SAX parser
main(...) parse(...) startDocument(...) startElement(...) characters(...) endElement( ) endDocument( )
What is the DOM?
The Document Object Model (DOM) provides a standard programming interface to a wide variety of applications. The XML DOM is designed to be used with any programming language and any operating system.
It is fully described in the W3C DOM specification
http://www.w3.org/DOM/
With the XML DOM, a programmer can create an XML document, navigate its structure, and add, modify, or delete its elements DOM provides generic access to DOM-compliant documents: add, edit, delete, manipulate DOM is language-independent The DOM is based on a tree view of your document. Nodes! Nodes! Nodes! DOM useful for CSS, HTML, XML DOM + client-side scripting + HTML = DHTML
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
DOM components
Document top-level view of the document, with access to all nodes (including root element)
createElement method - creates an element node createAttribute method - creates an attribute node createComment method - creates a comment node getDocumentElement method - returns root element appendChild method - appends a child node getChildNodes method - returns child nodes
DOM components II
Node represents a node - "A node is a reference to an element, its attributes, or text from the document."
cloneNode method - duplicates a node getNodeName method - returns the node name getNodeName method - returns the node's name getNodeType method - returns the node's type getNodeValue method - returns the node's value getParentNode method - returns the node's parent's name hasChildNodes method - true if has child nodes insertBefore method - stuffs child in before specified child removeChild method - removes the child node replaceChild method - replaces one child with another setNodeValue method - sets node's value
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
DOM components III
attribute represents an attribute node getAttribute method - gets attribute! getTagName method - gets element's name removeAttribute method - deletes it setAttribute method - sets att's value
Parsing the DOM
To read and update - create and manipulate - an XML document, you need an XML parser. The Microsoft XMLDOM parser features a programming model that:
Supports JavaScript, VBScript, Perl, VB, Java, C++ and more A COM component that comes with Microsoft Internet Explorer 5.0 Supports W3C XML 1.0 and XML DOM Supports DTD and validation
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
Creating an XML document object
JavaScript:
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM")
VBScript:
set xmlDoc = CreateObject("Microsoft.XMLDOM")
.asp:
set xmlDoc = Server.CreateObject("Microsoft.XMLDOM")
Adding in a new element
var link = document.createElement('a'); link.setAttribute('href', 'mypage.htm');
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
locating a slot in the document
by location:
document.childNodes[1].childNodes[0] Find the main document element (HTML), and find its second child (BODY), then look for its first child (DIV)
by ID:
document.getElementById('myDiv').appendChild(txt);
Hiding an element
document.childNodes[1].childNodes[1].childNodes[0] .style.display = "none";
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
Loading an XML document object into the parser
<script language="JavaScript"> var xmlDoc = new ActiveXObject("Microsoft.XMLDOM") xmlDoc.async="false" xmlDoc.load(note.xml") // ....... processing the document goes here </script>
Manually loading XML into the parser
<script language="JavaScript"> // load up variable var with some xml var text="<note>" text=text+"<to>John</to><from>Robert</from>" text=text+"<heading>Reminder</heading>" text=text+"<body>Don't forget your homework!</body>" text=text+"</note>" // now create the DO var xmlDoc = new ActiveXObject("Microsoft.XMLDOM") xmlDoc.async="false" xmlDoc.loadXML(text) // ....... process the document </script>
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
parseError object
document.write(xmlDoc.parseError.property) errorCode: Returns a long integer error code reason: Returns a string explaining the reason for the error line: Returns a long integer representing the line number for the error linePos: Returns a long integer representing the line position for the error srcText: Returns a string containing the line that caused the error url: Returns the url pointing the loaded document filePos: Returns a long integer file position of the error
Traversing nodes
set xmlDoc=CreateObject("Microsoft.XMLDOM") xmlDoc.async="false" xmlDoc.load("note.xml") for each x in xmlDoc.documentElement.childNodes document.write(x.nodename) document.write(": ") document.write(x.text) next
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
10
Calling XML nodes by name
var xmlDoc = new ActiveXObject("Microsoft.XMLDOM") xmlDoc.async="false" xmlDoc.load("note.xml")
document.write(xmlDoc.getElementsByTagName("from").item(0).text)
References
W3School DOM Tutorial
http://www.w3schools.com/dom/default.asp
MSXML 4.0 SDK
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
11
Reading List
W3School DOM Tutorial
http://www.w3schools.com/dom/default.asp
SWE 444 Internet & Web App. Development Dr. Abdallah Al-Sukairi - KFUPM
12
