1. Jagdish Gangolly State University of New York at Albany
XML Validation & DOM
Jagdish Gangolly
State University of New York at Albany
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

2. XML Validation & DOM SAX validation SAX vs. DOM
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

3. XML Validation Imports
Implement ContentHandler interface & Define the methods of the ContentHandler interface
Implement DTDHandler interface (*)
Instantiate parser & Register handlers
Turn on/off validation, namespace awareness, & parse the document
Parse & validate document (whole program)
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

4. Imports import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.DTDHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

5. Implement ContentHandler interface & Define the methods of the ContentHandler interface
class MyContentHandler implements ContentHandler {
private Locator locator;
public void setDocumentLocator(Locator locator) { }
public void startDocument() throws SAXException { …
public void skippedEntity(String name) throws SAXException {
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

6. Implement DTDHandler interface (*)
The DTDHandler provides callback methods
for during the process of reading and parsing
DTDs. Since it does not define events during
validation, but only those occuring during
reading of DTDs, they are not crucial.
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

7. Instantiate parser & Register Handlers
// Get instances of our handlers
ContentHandler contentHandler = new MyContentHandler();
ErrorHandler errorHandler = new MyErrorHandler();
DTDHandler dtdHandler = new MyDTDHandler();
// Instantiate a parser
XMLReader parser = XMLReaderFactory.createXMLReader(
"org.apache.xerces.parsers.SAXParser");
// Register the content handler
parser.setContentHandler(contentHandler);
// Register the error handler
parser.setErrorHandler(errorHandler);
// Register the DTD handler
parser.setDTDHandler(dtdHandler);
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

8. Turn on/off validation, namespace awareness, & Parse document
// Turn on validation
parser.setFeature
("
// Turn off namespace awareness not needed for Xerces 1.2+
(" false);
// Parse the document
parser.parse(uri);
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

9. Parse & validate document (whole program)
//Imports
import java.io.IOException;
import org.xml.sax.Attributes;
import org.xml.sax.ContentHandler;
import org.xml.sax.DTDHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;
import org.xml.sax.helpers.XMLReaderFactory;
public class SAXParserDemo {
public void performDemo(String uri) {
System.out.println("Parsing XML File: " + uri + "\n\n");
ContentHandler contentHandler = new MyContentHandler();
ErrorHandler errorHandler = new MyErrorHandler();
DTDHandler dtdHandler = new MyDTDHandler();
(Continued next slide)
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

10. Parse & validate document (whole program)
try {
XMLReader parser = XMLReaderFactory.createXMLReader(
"org.apache.xerces.parsers.SAXParser");
parser.setContentHandler(contentHandler);
parser.setErrorHandler(errorHandler);
parser.setDTDHandler(dtdHandler);
parser.setFeature(" true);
parser.setFeature(" false);
parser.parse(uri);
} catch (IOException e) {
System.out.println("Error reading URI: " + e.getMessage());
} catch (SAXException e) {
System.out.println("Error in parsing: " + e.getMessage()); }
public static void main(String[] args) {
if (args.length != 1) {
System.out.println("Usage: java SAXParserDemo [XML URI]");
System.exit(0);
String uri = args[0];
SAXParserDemo parserDemo = new SAXParserDemo();
parserDemo.performDemo(uri);
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

11. SAX vs. DOM
SAX is sequential, so it does not allow for random access to a document
No concept of sibling, next,… elements in SAX, so difficult to move laterally
DOMtree representation consumes memory
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

12. DOM Imports DOMParserDemo class Command line input Parse document
PrintNode method
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

13. DOM: Imports import java.io.IOException;
import org.xml.sax.SAXException;
import org.w3c.dom.Document;
import org.w3c.dom.DocumentType;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.apache.xerces.parsers.DOMParser;
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

14. DOM: DOMParserDemo class
public class DOMParserDemo {
PerformDemo method to parse the document
Method to print nodes
Main method to obtain uri to be parsed }
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

15. DOM: Main method to obtain uri to be parsed
public static void main(String[] args) {
if (args.length != 1) {
System.out.println("Usage: java DOMParserDemo [XML
URI]");
System.exit(0); }
String uri = args[0];
DOMParserDemo parserDemo = new DOMParserDemo();
parserDemo.performDemo(uri);
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

16. DOM: Method to print nodes I
public void printNode(Node node, String indent) {
switch (node.getNodeType()) {
case Node.DOCUMENT_NODE:
System.out.println("<xml version=\"1.0\">\n");
NodeList nodes = node.getChildNodes();
if (nodes != null) {
for (int i=0; i<nodes.getLength(); i++) {
printNode(nodes.item(i), ""); }
break;
case Node.ELEMENT_NODE:
case Node.TEXT_NODE:
case Node.CDATA_SECTION_NODE:
case Node.PROCESSING_INSTRUCTION_NODE:
case Node.ENTITY_REFERENCE_NODE:
case Node.DOCUMENT_TYPE_NODE:
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

17. DOM: Method to print nodes II
case Node.ELEMENT_NODE:
String name = node.getNodeName();
System.out.print(indent + "<" + name);
NamedNodeMap attributes = node.getAttributes();
for (int i=0; i<attributes.getLength(); i++) {
Node current = attributes.item(i);
System.out.print(" " + current.getNodeName()
+ "=\"" + current.getNodeValue() + "\""); }
System.out.println(">");
NodeList children = node.getChildNodes();
if (children != null) {
for (int i=0; i<children.getLength(); i++) {
printNode(children.item(i), indent + " ");
System.out.println(indent + "</" + name + ">");
break;
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

18. DOM: Method to print nodes III
case Node.TEXT_NODE:
case Node.CDATA_SECTION_NODE:
System.out.print(node.getNodeValue());
break;
case Node.PROCESSING_INSTRUCTION_NODE:
System.out.println("<?" + node.getNodeName() +
" " + node.getNodeValue() + "?>");
case Node.ENTITY_REFERENCE_NODE:
System.out.println("&" + node.getNodeName() + ";");
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018

19. DOM: Method to print nodes III
case Node.DOCUMENT_TYPE_NODE:
DocumentType docType = (DocumentType)node;
System.out.print("<!DOCTYPE " + docType.getName());
if (docType.getPublicId() != null) {
System.out.print(" PUBLIC \"" +
docType.getPublicId() + "\" ");
} else {
System.out.print(" SYSTEM "); }
System.out.println("\"" + docType.getSystemId() +
"\">");
break;
Acc 683, Spring, 2001 Jagdish S. Gangolly
11/19/2018