This document provides an overview of Java and XML processing using DOM, SAX, and JDOM. It outlines the key components and approaches for each, including parsing XML files into a DOM or SAX event model, traversing nodes and elements, and accessing attributes and content. JDOM is presented as an alternative Java DOM that supports Java collections and provides additional convenience methods for working with XML content.

1. Java and XML
(DOM, SAX, JDOM)
Raji GHAWI
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2. Outlines
1.
2.
3.
DOM
SAX
JDOM
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3. 1.
DOM
Document Object Model

4. <inventory>
<book year="2000">
<title>Snow Crash</title>
<author>Neal Stephenson</author>
<publisher>Spectra</publisher>
<isbn>0553380958</isbn>
<price>14.95</price>
</book>
<book year="2005">
<title>Burning Tower</title>
<author>Larry Niven</author>
<author>Jerry Pournelle</author>
<publisher>Pocket</publisher>
<isbn>0743416910</isbn>
<price>5.99</price>
</book>
<book year="1995">
<title>Zodiac</title>
<author>Neal Stephenson</author>
<publisher>Spectra</publisher>
<isbn>0553573862</isbn>
<price>7.50</price>
</book>
<!-- more books... -->
</inventory>
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5. Import required packages
import javax.xml.parsers.*;
import org.w3c.dom.*;
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6. Create the parser
DOM parser factory
try {
DocumentBuilderFactory factory =
DocumentBuilderFactory.newInstance();
DocumentBuilder builder = factory.newDocumentBuilder();
// ....
} catch (Exception e) {
e.printStackTrace(System.out);
}
DOM parser
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IOException
ParserConfigurationException
SAXException
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7. Parse an XML file
Document document = builder.parse("../inventory.xml");
the entire XML file (as a tree)
(the Document Object Model)
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8. Root element
the root element
Element root = document.getDocumentElement();
System.out.println(root.getTagName());
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9. Nodes
Node
Text
Element
may have children
Attr
leaves
Operations on Nodes
Element
Text
Attr
getNodeName()
tag name
"#text"
name of attribute
getNodeValue()
null
text contents
value of attribute
getNodeType()
ELEMENT_NODE
TEXT_NODE
ATTRIBUTE_NODE
getAttributes()
NamedNodeMap
null
null
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10. Distinguishing Node types
switch(node.getNodeType()) {
case Node.ELEMENT_NODE:
Element element = (Element)node;
...;
break;
case Node.TEXT_NODE:
Text text = (Text)node;
...
break;
case Node.ATTRIBUTE_NODE:
Attr attr = (Attr)node;
...
break;
default: ...
}
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11. Operations on Nodes







getParentNode()
getFirstChild()
getNextSibling()
getPreviousSibling()
getLastChild()
hasAttributes()
hasChildNodes()
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12. Travel through children nodes
if (element.hasChildNodes()) {
Node child = element.getFirstChild();
while (child != null) {
// ....
child = child.getNextSibling();
}
}
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13. Operations for Elements





String getTagName()
boolean hasAttribute(String name)
String getAttribute(String name)
boolean hasAttributes()
NamedNodeMap
getAttributes()
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14. NamedNodeMap



Node getNamedItem(String name)
int getLength()
Node item(int index)
NamedNodeMap map = element.getAttributes();
for (int i = 0; i < map.getLength(); i++) {
Attr attr = (Attr) map.item(i);
System.out.println(attr.getNodeName()
+ "='"+ attr.getNodeValue()+"'");
}
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15. Operations on Texts



String getData()
int getLength()
String substringData(int offset, int count)
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16. Operations on Attrs



String getName()
Element getOwnerElement()
String getValue()
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17. 2.
SAX
Simple API for XML

18. Import required packages
import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;
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19. Create the parser
// Create a parser factory
SAXParserFactory factory = SAXParserFactory.newInstance();
// Tell factory that the parser must understand namespaces
factory.setNamespaceAware(true);
try {
// Make the parser
SAXParser saxParser = factory.newSAXParser();
XMLReader parser = saxParser.getXMLReader();
} catch(Exception e){
e.printStackTrace();
}
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IOException
ParserConfigurationException
SAXException
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20. Parse an XML file
// Create a handler
Handler handler = new Handler();
// Tell the parser to use this handler
parser.setContentHandler(handler);
// Finally, read and parse the document
parser.parse("./inventory.xml");
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21. SAX handlers

A callback handler for SAX must implement four interfaces:
 interface ContentHandler
 interface DTDHandler
 interface EntityResolver
 interface ErrorHandler

It is easier to use an adapter class
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22. Class DefaultHandler



DefaultHandler is in package org.xml.sax.helpers
DefaultHandler implements ContentHandler, DTDHandler,
EntityResolver, and ErrorHandler
DefaultHandler is an adapter class


Provides empty methods for every method declared in each of the four
interfaces
To use this class, extend it and override the methods that are
important to your application
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23. The Handler class
class Handler extends DefaultHandler {
// SAX calls this method when it encounters a start tag
public void startElement(String namespaceURI,
String localName,
String qualifiedName,
Attributes attributes) throws SAXException {
System.out.println("startElement: " + qualifiedName);
}
// SAX calls this method to pass in character data
public void characters(char ch[], int start, int length)
throws SAXException {
System.out.println("characters: "" +
new String(ch, start, length) + """);
}
// SAX call this method when it encounters an end tag
public void endElement(String namespaceURI,
String localName,
String qualifiedName) throws SAXException {
System.out.println("endElement: /" + qualifiedName);
}
}
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24. <inventory>
<book year="2000">
<title>Snow Crash</title>
<author>Neal Stephenson</author>
<publisher>Spectra</publisher>
<isbn>0553380958</isbn>
<price>14.95</price>
</book>
<book year="2005">
<title>Burning Tower</title>
<author>Larry Niven</author>
<author>Jerry Pournelle</author>
<publisher>Pocket</publisher>
<isbn>0743416910</isbn>
<price>5.99</price>
</book>
<book year="1995">
<title>Zodiac</title>
<author>Neal Stephenson</author>
<publisher>Spectra</publisher>
<isbn>0553573862</isbn>
<price>7.50</price>
</book>
<!-- more books... -->
</inventory>
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startElement: inventory
characters: "
"
startElement: book
characters: "
"
startElement: title
characters: "Snow Crash"
endElement: /title
characters: "
"
startElement: author
characters: "Neal Stephenson"
endElement: /author
characters: "
"
startElement: publisher
characters: "Spectra"
endElement: /publisher
characters: "
...
"
endElement: /book
...
endElement: /inventory
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25. Attributes









getLength()
getLocalName(index)
getQName(index)
getValue(index)
getType(index)
int getIndex(String qualifiedName)
int getIndex(String uri, String localName)
String getValue(String qualifiedName)
String getValue(String uri, String localName)
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26. Attributes
public void startElement(String namespaceURI,
String localName,
String qualifiedName,
Attributes attributes) throws SAXException {
// ....
for (int i = 0; i < attributes.getLength(); i++) {
String attName = attributes.getQName(i);
String attValue = attributes.getValue(i);
System.out.println(attName+"='"+attValue+"'");
}
// ....
}
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27. 3.
JDOM
Java DOM

28. Import required packages
import
import
import
import
org.jdom.*;
org.jdom.input.*;
org.jdom.output.*;
org.jdom.adapters.*;
org.jdom
org.jdom.adapters
org.jdom.input
org.jdom.output
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29. Create the parser
try {
SAXBuilder builder = new SAXBuilder();
// ....
} catch (IOException ioe) {
ioe.printStackTrace();
} catch (JDOMException je) {
je.printStackTrace();
}
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30. Parse an XML file
Document document = builder.build("../inventory.xml");
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31. Root element
Element root = document.getRootElement();
System.out.println(root.getName());
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32. Print out the document
XMLOutputter outputter = new XMLOutputter();
outputter.output(document, System.out);
StringWriter sw = new StringWriter();
XMLOutputter outputter = new XMLOutputter();
outputter.output(document, sw);
String xml = sw.toString();
Advantage 1:
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Output facility
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33. Get children
• Get all direct children
List allChildren = element.getChildren();
• Get all direct children with a given name
List namedChildren = element.getChildren("book");
• Get the first child with a given name
Element child = element.getChild("book");
Advantage 2:
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supports Java Collections
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34. Travel through children nodes
List children = element.getChildren();
for (int i = 0; i < children.size(); i++) {
Element elem = (Element) children.get(i);
// ....
}
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35. Get attributes
• Get all attributes
List attrs = element.getAttributes();
for (int i = 0; i < attrs.size(); i++)
Attribute attr = (Attribute) attrs.get(i);
System.out.println(attr.getName()+" = "+attr.getValue());
}
• Get an attribute with a given name
Attribute attr = element.getAttribute("year");
• Get an attribute value with a given name
String value = element.getAttributeValue("year");
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36. Reading Element Content
• The text content is directly available
String content = element.getText();
• Remove extra whitespace
String content = element.getTextTrim();
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37. Mixed Content
• Sometimes an element may contain comments, text content, and children
<table>
<!-- Some comment -->
Some text
<tr>Some child</tr>
</table>
String text = table.getTextTrim();
Element tr = table.getChild("tr");
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38. Mixed Content
List mixedContent = table.getContent();
Iterator iter = mixedContent.iterator();
while (iter.hasNext()) {
Object obj = iter.next();
if (obj instanceof Comment) {
System.out.println("Comment: " + obj);
} else if (obj instanceof String) {
System.out.println("String: " + obj);
} else if (obj instanceof Element) {
System.out.println("Element: " + ((Element)obj).getName());
}
}
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39. References

Processing XML with Java; Elliotte Rusty Harold
http://cafeconleche.org/books/xmljava/chapters/index.html
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