SAX Parser

[Jimmy kalra]

import org.xml.sax.*;
import org.xml.sax.helpers.*;
import javax.swing.*;
import javax.swing.tree.*;
import java.util.*;


public class TreeViewer extends DefaultHandler {

  private Stack nodes;
  
  // Initialize the per-document data structures
  public void startDocument() throws SAXException {
    
    // The stack needs to be reinitialized for each document
    // because an exception might have interrupted parsing of a
    // previous document, leaving an unempty stack.
    nodes = new Stack();
	System.out.println(nodes);
    
  }
 
  // Make sure we always have the root element
  private TreeNode root;
 
  // Initialize the per-element data structures
  public void startElement(String namespaceURI, String localName,
   String qualifiedName, Attributes atts) {
  
    String data;
    if (namespaceURI.equals("")) data = localName;
    else {
      data = '{' + namespaceURI + "} " + qualifiedName;
	  System.out.println(data);
    }
    MutableTreeNode node = new DefaultMutableTreeNode(data);
    try {
      MutableTreeNode parent = (MutableTreeNode) nodes.peek();
	  System.out.println(parent.getChildCount());
      parent.insert(node, parent.getChildCount()); 
    }
    catch (EmptyStackException e) {
      root = node; 
    }
    nodes.push(node);
   
  }
  
  public void endElement(String namespaceURI, String localName,
   String qualifiedName) {
    nodes.pop();
  }

  // Flush and commit the per-document data structures
  public void endDocument() {
    
    JTree tree = new JTree(root);
    JScrollPane treeView = new JScrollPane(tree);
    JFrame f  = new JFrame("XML Tree");
    
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.getContentPane().add(treeView);
    f.pack();
    f.show();
    
  }
    

  public static void main(String[] args) {
      
    try {
      XMLReader parser = XMLReaderFactory.createXMLReader(
        "org.apache.xerces.parsers.SAXParser"
      );
      ContentHandler handler = new TreeViewer();
      parser.setContentHandler(handler);
      for (int i = 0; i < args.length; i++) {  
        parser.parse(args[i]);
      }
    }
    catch (Exception e) {
      System.err.println(e);
    }
  
  }   // end main()
   
} // end TreeViewer

what the action perform by this statement

MutableTreeNode parent = (MutableTreeNode) nodes.peek(); 

??

[Tim Moores]

Have you read the javadoc entry for that method? What did you understand from that?

[Jimmy kalra]

thanks , now i understand the working of this statement in program........