1. Schema Data Processing
Unit 10

2. Key Concepts
DOM basics
DOM components
Nodes
Node types
Node hierarchy

3. Document Object Model In-memory data storage.
Hierarchical data storage model.
Allows navigation between nodes.
Allows data insertion and data retrieval from the DOM
Language-neutral representation of data
Supported by .NET languages

4. Some DOM-based parsers

5. DOM Components

6. XML Nodes <root> <name> <first>Joe</first>
<middle/>
<last>Smith</last>
</name>

7. Node Types Node type Description Document
The document root, which is a container for all document nodes.
DocumentFragment
Temporary containing holding a subset of document nodes.
DocumentType
A <!DOCTYPE…> node.
EntityReference
Entity reference text.
Element
An element node.
Attr
An attributed of an element, represented as a node.

8. Node Types (cont'd) Node type Description ProcessingInstruction
Node containing processing instruction information.
Comment
Comment node.
Text
Text value of an element or attribute.
CDATASection
Node representing a CDATA section.
Entity
DTD <!ENTITY…> declaration.
Notation
DTD notation declaration.

9. Creating an XML Document
1 // Fig : BuildXml.java
2 // Creates element node, attribute node, comment node,
3 // processing instruction and a CDATA section. 4
5 import java.io.*;
6 import org.w3c.dom.*;
7 import org.xml.sax.*;
8 import javax.xml.parsers.*;
9 import com.sun.xml.tree.XmlDocument; 10
11 public class BuildXml {
12 private Document document; 13
14 public BuildXml()
15 { 16
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance(); 19
try { 21
// get DocumentBuilder
DocumentBuilder builder =
factory.newDocumentBuilder(); 25

10. Creating an XML Document (cont'd)
// create root node
document = builder.newDocument(); }
catch ( ParserConfigurationException pce ) {
pce.printStackTrace(); } 32
Element root = document.createElement( "root" );
document.appendChild( root ); 35
// add a comment to XML document
Comment simpleComment = document.createComment(
"This is a simple contact list" );
root.appendChild( simpleComment ); 40
// add a child element
Node contactNode = createContactNode( document );
root.appendChild( contactNode ); 44
// add a processing instruction
ProcessingInstruction pi =
document.createProcessingInstruction(
"myInstruction", "action silent" );
root.appendChild( pi ); 50

11. Creating an XML Document (cont'd)
// add a CDATA section
CDATASection cdata = document.createCDATASection(
53` "I can add <, >, and ?" );
root.appendChild( cdata ); 55
try { 57
// write the XML document to a file
( (XmlDocument) document).write( new FileOutputStream(
"myDocument.xml" ) ); }
catch ( IOException ioe ) {
ioe.printStackTrace(); }
65 } 66
67 public Node createContactNode( Document document )
68 { 69
// create FirstName and LastName elements
Element firstName = document.createElement( "FirstName" );
Element lastName = document.createElement( "LastName" ); 73
firstName.appendChild( document.createTextNode( "Sue" ) );
lastName.appendChild( document.createTextNode( "Green" ) ); 76

12. Creating an XML Document (cont'd)
// create contact element
Element contact = document.createElement( "contact" ); 79
// create an attribute
Attr genderAttribute = document.createAttribute( "gender" );
genderAttribute.setValue( "F" ); 83
// append attribute to contact element
contact.setAttributeNode( genderAttribute );
contact.appendChild( firstName );
contact.appendChild( lastName );
return contact;
89 } 90
91 public static void main( String args[] )
92 {
BuildXml buildXml = new BuildXml();
94 }
95 }

13. XML Document Result 1 // Fig. 8.15 : TraverseDOM.java
2 // Traverses DOM and prints various nodes. 3
4 import java.io.*;
5 import org.w3c.dom.*;
6 import org.xml.sax.*;
7 import javax.xml.parsers.*;
8 import com.sun.xml.tree.XmlDocument; 9
10 public class TraverseDOM {
11 private Document document; 12
13 public TraverseDOM( String file )
14 {
try { 16
// obtain the default parser
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
factory.setValidating( true );
DocumentBuilder builder = factory.newDocumentBuilder(); 22
// set error handler for validation errors
builder.setErrorHandler( new MyErrorHandler() ); 25

14. XML Document Result (cont’d)
// obtain document object from XML document
document = builder.parse( new File( file ) );
processNode( document ); }
catch ( SAXParseException spe ) {
System.err.println(
"Parse error: " + spe.getMessage() );
System.exit( 1 ); }
catch ( SAXException se ) {
se.printStackTrace(); }
catch ( FileNotFoundException fne ) {
System.err.println( "File \'"
file + "\' not found. " );
System.exit( 1 ); }
catch ( Exception e ) {
e.printStackTrace(); }
46 } 47
48 public void processNode( Node currentNode )
49 {
switch ( currentNode.getNodeType() ) { 51 22
// set error handler for validation errors
builder.setErrorHandler( new MyErrorHandler() ); 25

15. XML Document Result (cont’d)
// process a Document node
case Node.DOCUMENT_NODE:
Document doc = ( Document ) currentNode; 55
System.out.println(
"Document node: " + doc.getNodeName() +
"\nRoot element: " +
doc.getDocumentElement().getNodeName() );
processChildNodes( doc.getChildNodes() );
break; 62
// process an Element node
case Node.ELEMENT_NODE:
System.out.println( "\nElement node: " +
currentNode.getNodeName() );
NamedNodeMap attributeNodes =
currentNode.getAttributes(); 69
for ( int i = 0; i < attributeNodes.getLength(); i++){
Attr attribute = ( Attr ) attributeNodes.item( i ); 72
System.out.println( "\tAttribute: " +
attribute.getNodeName() + " ; Value = " +
attribute.getNodeValue() ); } 77
processChildNodes( currentNode.getChildNodes() );
break; 80
XML Document Result (cont’d)

16. XML Document Result (cont’d)
// process a text node and a CDATA section
case Node.CDATA_SECTION_NODE:
case Node.TEXT_NODE:
Text text = ( Text ) currentNode; 85
if ( !text.getNodeValue().trim().equals( "" ) )
System.out.println( "\tText: " +
text.getNodeValue() );
break; }
91 } 92
93 public void processChildNodes( NodeList children )
94 {
if ( children.getLength() != 0 ) 96
for ( int i = 0; i < children.getLength(); i++)
processNode( children.item( i ) );
99 }
100
public static void main( String args[] ) {
if ( args.length < 1 ) {
System.err.println(
"Usage: java TraverseDOM <filename>" );
System.exit( 1 ); }
108
TraverseDOM traverseDOM = new TraverseDOM( args[ 0 ] ); }
111 }
XML Document Result (cont’d)