tutorial about processing XML document using Java. It covers DOM, SAX, and JDOM APIs.

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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