This section provides a tutorial example on how to parse an XML file and print it back in a tree format using SAX interface in Java - JDK 1.4.1.
Let's build a simple SAX based XML browser by implementing those event handler methods
defined in the org.xml.sax.DocumentHandler interface:
/**
* SAXBrowser.java
* Copyright (c) 2002 by Dr. Herong Yang. http://www.herongyang.com/
*/
import java.io.File;
import java.io.IOException;
import javax.xml.parsers.SAXParserFactory;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.ParserConfigurationException;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;
class SAXBrowser {
public static void main(String[] args) {
try {
File x = new File(args[0]);
SAXParserFactory f = SAXParserFactory.newInstance();
SAXParser p = f.newSAXParser();
DefaultHandler h = new MyContentHandler();
p.parse(x,h);
} catch (ParserConfigurationException e) {
System.out.println(e.toString());
} catch (SAXException e) {
System.out.println(e.toString());
} catch (IOException e) {
System.out.println(e.toString());
}
}
private static class MyContentHandler extends DefaultHandler {
static String p = "_";
public void startDocument() throws SAXException {
System.out.println("Starting document...");
}
public void endDocument() throws SAXException {
System.out.println("Ending document...");
}
public void startElement(String ns, String sName, String qName,
Attributes attrs) throws SAXException {
String eName = sName;
if (sName.equals("")) eName = qName;
System.out.println("e"+p+eName);
if (attrs!=null) {
for (int i=0; i<attrs.getLength(); i++) {
String aName = attrs.getLocalName(i);
if (aName.equals("")) aName = attrs.getQName(i);
System.out.println("a"+p+" "+aName+"="
+attrs.getValue(i));
}
}
p = p + "_";
}
public void endElement(String ns, String sName, String qName)
throws SAXException {
p = p.replaceFirst("__", "_");
}
public void characters(char buf[], int offset, int len)
throws SAXException {
String s = new String(buf, offset, len);
System.out.println("c"+p+s);
}
public void ignorableWhitespace(char buf[], int offset, int len)
throws SAXException {
String s = new String(buf, offset, len);
System.out.println("i"+p+s);
}
}
}
Note that:
I cheated a little bit. Instead of implementing the ContentHandler interface
directly, I extended the DefaultHandler class, which implemented handling methods
for all events (by doing nothing). In this way, I only need to override the handling
methods that I am interested in.
"_" character is used to indent sub-elements in nested elements.
