5 Processing XML

5 - 2 Parsing XML documents  Document Object Model (DOM)  Simple API for XML (SAX) Class generation Overview

5 - 3 What's the Problem? The XML Handbook Goldfarb Prescod Prentice Hall XML Design Spencer Wrox Press... ? Book ?

5 - 4 Parsing XML Documents Document Tree Parser Docu- ment DTD / Schema Application implements DocumentHandler endDocument startDocument endElement startElement DOM SAX

5 - 5 Parser Project X (Sun Microsystems) Ælfred (Microstar Software) XML4J (IBM) Lark (Tim Bray) MSXML (Microsoft) XJ (Data Channel) Xerces (Apache)...

5 - 6 Prescod book Prentice Hall The XML Handbook Goldfarb Prescod Prentice Hall XML Design Spencer Wrox Press... The Document Object Model XML Document Structure The XML Handbook Goldfarb655 books book publisherpagesisbnauthortitle...

5 - 7 The Document Object Model Provides a standard interface for access to and manipulation of XML structures. Represents documents in the form of a hierarchy of nodes. Is platform- and programming-language-neutral Is a recommendation of the W3C (October 1, 1998) Is implemented by many parsers

5 - 8 DOM - Structure Model Document Node NodeList Element Prescod book Prentice Hall The XML Handbook Goldfarb655 books book publisherpagesisbnauthortitle...

5 - 9 The Document Interface Method Result docType implementation documentElement getElementsByTagName(String) createTextNode(String) createComment(String) createElement(String) create CDATASection(String) DocumentType DOMImplementation Element NodeList String Comment Element CDATASection

The Node Interface Method Result nodeName nodeValue nodeType parentNode childNodes firstChild lastChild previousSibling nextSibling attributes insertBefore(Node new,Node ref) replaceChild(Node new,Node old) removeChild(Node) hasChildNode String short Node NodeList Node NodeNamedMap Node Boolean

Node Types / Node Names Result: NodeType /NodeName Node Node Node Fields Type Name ELEMENT_NODE 1 tagName ATTRIBUTE_NODE 2 name of attribute TEXT_NODE 3 "#text" CDATA_SECTION_NODE 4 "#cdata-section" ENTITY_REFERENCE_NODE 5 name of entity referenced ENTITY_NODE 6 entity name PROCESSING_INSTRUCTION_NODE 7 target COMMENT_NODE 8 "#comment" DOCUMENT_NODE 9 "#document" DOCUMENT_TYPE_NODE10 document type name DOCUMENT_FRAGMENT_NODE11 "#document-fragment" NOTATION_NODE12 notation name

The NodeList Interface Method Result length item(int) Int Node

The Element Interface Method Result tagName getAttribute(String) setAttribute(String name, String value) removeAttribute(String) getAttributeNode(String) setAttributeNode(Attr) removeAttributeNode(String) getElementsByTagName String Attr NodeList

DOM Methods for Navigation firstChildlastChild nextSiblingpreviousSibling parentNode getElementsByTagName childNodes (length, item())

DOM Methods for Manipulation appendChild insertBefore replaceChild removeChild createElement createAttribute createTextNode

Example Goldfarb Spencer books book author Prescod doc.documentElement.childNodes.item(0).getElementsByTagName("author"). item(1).childNodes.item(0).data doc.documentElement.childNodes.item(0).getElementsByTagName("author"). item(1).childNodes.item(0).data Root Node DOM Object TextBooks second Author Text Subnodes first thereof first Book Authors

Script DOM Example DOM Example var doc, root, book1, authors, author2; doc = new ActiveXObject("Microsoft.XMLDOM"); doc.async = false; doc.load("books.xml"); if (doc.parseError != 0) alert(doc.parseError.reason); else { root = doc.documentElement; document.write("Name of Root node: " + root.nodeName + " "); document.write("Type of Root node: " + root.nodeType + " "); book1 = root.childNodes.item(0); authors = book1.getElementsByTagName("author"); document.write("Number of authors: " + authors.length + " "); author2 = authors.item(1); document.write("Name of second author: " + author2.childNodes.item(0).data);} DOM Example DOM Example var doc, root, book1, authors, author2; doc = new ActiveXObject("Microsoft.XMLDOM"); doc.async = false; doc.load("books.xml"); if (doc.parseError != 0) alert(doc.parseError.reason); else { root = doc.documentElement; document.write("Name of Root node: " + root.nodeName + " "); document.write("Type of Root node: " + root.nodeType + " "); book1 = root.childNodes.item(0); authors = book1.getElementsByTagName("author"); document.write("Number of authors: " + authors.length + " "); author2 = authors.item(1); document.write("Name of second author: " + author2.childNodes.item(0).data);}

SAX - Simple API for XML Docu- ment DTD Application endDocument startDocument endElement startElement Parser

SAX - Simple API for XML Event-driven parsing model "Don't call the DOM, the parser calls you." Developed by the members of the XML-DEV Mailing List Released on May 11, 1998 Supported by many parsers but Ælfred is the saxon king.

Procedure DOM  Creating a parser instance  Parsing the whole document  Processing the DOM tree SAX  Creating a parser instance  Registrating event handlers with the parser  Parser calls the event handler during parsing

Namespace Support <orderxmlns=" xmlns:bk=" xmlns:cust=" >... XML Handbook

Access to Qualified Elements Node "book" bk:book bk book Interface "Node" DOM Level 2 Method nodeName namespaceURI prefix localName qName uri localName SAX 2.0 startElement

Generation of Data Structures DTD / Schema 'yacht' Generation 01yacht 05name 05details 10type Class Processing Mona Lisa Any text describing this yacht 147 GULFSTAR 55 ength> yacht 05VENTANA 05details 10GULFSTAR 55 Object

Summary To avoid expensive text processing, applications use an XML parser that creates a DOM tree of a document. The DOM provides a standardized API to access the content of documents and to manipulate them. Alternatively or additionally, applications can work event-based using the SAX interface, which is provided by many parsers.