Question

Hi, I am trying to create an XML JTree viewer using the DOM parser instead of the SAX parser, I am having trouble changing my code in order to utilize the DOM parser to extract the XML data into the tree structure. Would you be able to explain what changes should be made to the code in order to use the DOM parser instead of the SAX parser?

// Java Packages //     
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextField;
import javax.swing.JTree;
import javax.swing.WindowConstants;
import javax.swing.filechooser.FileFilter;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.Attributes;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

// JTree model viewer //
public class XMLTreeViewer extends DefaultHandler {

private JTree xmlJTree;
DefaultTreeModel treeModel;
int lineCounter;

DefaultMutableTreeNode base = new DefaultMutableTreeNode("XML Viewer in Tree Structure");
static XMLTreeViewer treeViewer = null;
JTextField txtFile = null;

// Method to begin to using SAX Parser starting from base root branching out to child nodes //
@Override
public void startElement(String uri, String localName, String tagName, Attributes attr) throws SAXException {

DefaultMutableTreeNode current = new DefaultMutableTreeNode(tagName);

base.add(current);

base = current;

for (int i = 0; i < attr.getLength(); i++) {

DefaultMutableTreeNode currentAtt = new DefaultMutableTreeNode(attr.getLocalName(i) + " = "

+ attr.getValue(i));

base.add(currentAtt);
}

}

// error handling for entity parsing if not caught
public void skippedEntity(String name) throws SAXException {

System.out.println("Skipped Entity: '" + name + "'");
}

// Initial view of Jtree model idle //
@Override
public void startDocument() throws SAXException {

super.startDocument();
base = new DefaultMutableTreeNode("XML Viewer");

((DefaultTreeModel) xmlJTree.getModel()).setRoot(base);

}

// Adding Description to each subsequent child node //
public void characters(char[] ch, int start, int length) throws SAXException {

String s = new String(ch, start, length).trim();

if (!s.equals("")) {

DefaultMutableTreeNode current = new DefaultMutableTreeNode("Description : " + s);

base.add(current);

}

}

// End of current child node branching stopping at parent //
public void endElement(String namespaceURI, String localName, String qName) throws SAXException {

base = (DefaultMutableTreeNode) base.getParent();

}

// Main Program Start //
public static void main(String[] args) {

treeViewer = new XMLTreeViewer();

// treeViewer.xmlSetUp();

treeViewer.createUI();

}

// Ends current XML file parsing and reloads //
@Override
public void endDocument() throws SAXException {

// Refresh JTree

((DefaultTreeModel) xmlJTree.getModel()).reload();

//Comment this out if you want the trees to be closed by default
//expandAll(xmlJTree);

}

// Expansion of Jtree structure levels //
public void expandAll(JTree tree) {

int row = 0;

while (row < tree.getRowCount()) {

tree.expandRow(row);

row++;
}

}

// Parser takes in current XML file to parse //
public void xmlSetUp(File xmlFile) {

try {

SAXParserFactory fact = SAXParserFactory.newInstance();

SAXParser parser = fact.newSAXParser();

parser.parse(xmlFile, this);

} catch (Exception e) {

}

}

// Jtree View component //
public void createUI() {

treeModel = new DefaultTreeModel(base);
xmlJTree = new JTree(treeModel);

JScrollPane scrollPane = new JScrollPane(xmlJTree);
JFrame windows = new JFrame();

windows.setTitle("XML file JTree Viewer using SAX Parser");

JPanel pnl = new JPanel();
pnl.setLayout(null);

JLabel lbl = new JLabel("File :");
txtFile = new JTextField("Selected File Name Here");

JButton btn = new JButton("Import File");
btn.addActionListener(new ActionListener() {

// JFile Chooser is opened after JButton interaction //
@Override
public void actionPerformed(ActionEvent evt) {

JFileChooser fileopen = new JFileChooser();
FileFilter filter = new FileNameExtensionFilter("xml files", "xml");

fileopen.addChoosableFileFilter(filter);
int ret = fileopen.showDialog(null, "Open file");

if (ret == JFileChooser.APPROVE_OPTION) {

File file = fileopen.getSelectedFile();
txtFile.setText(file.getPath() + File.separator + file.getName());
xmlSetUp(file);

}

}

});

// Pane window size and interaction //
lbl.setBounds(0, 0, 100, 30);
txtFile.setBounds(110, 0, 250, 30);

btn.setBounds(360, 0, 100, 30);
scrollPane.setBounds(0, 50, 500, 600);

pnl.add(lbl);
pnl.add(txtFile);

pnl.add(btn);
pnl.add(scrollPane);

windows.add(pnl);
windows.setSize(500, 700);

windows.setVisible(true);
windows.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

   }

   }

Answer 1

I have made changes in the code to parse the file using the DOM Parser. In xmlSetup() method I have made changes and commented it. You can uncomment the DOM code and comment your SAX Parser code. I have not tested the code with a XML doc. I hope this answer your questions.

Thanks.

------------------------------------------------------------------------------------------------------------------------------------------------------

// Java Packages //     

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.io.File;

import javax.swing.JButton;

import javax.swing.JFileChooser;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

import javax.swing.JScrollPane;

import javax.swing.JTextField;

import javax.swing.JTree;

import javax.swing.WindowConstants;

import javax.swing.filechooser.FileFilter;

import javax.swing.filechooser.FileNameExtensionFilter;

import javax.swing.tree.DefaultMutableTreeNode;

import javax.swing.tree.DefaultTreeModel;

import javax.xml.parsers.SAXParser;

import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;

import org.xml.sax.SAXException;

import org.xml.sax.helpers.DefaultHandler;

/*-------CHANGES IN CODE FOR DOM PARSER--------

//Import following packages

import org.w3c.dom.*;

import javax.xml.parsers.*;

import java.io.*;

*/

// JTree model viewer //

public class XMLTreeViewer extends DefaultHandler {

private JTree xmlJTree;

DefaultTreeModel treeModel;

int lineCounter;

DefaultMutableTreeNode base = new DefaultMutableTreeNode("XML Viewer in Tree Structure");

static XMLTreeViewer treeViewer = null;

JTextField txtFile = null;

// Method to begin to using SAX Parser starting from base root branching out to child nodes //

@Override

public void startElement(String uri, String localName, String tagName, Attributes attr) throws SAXException

{

    DefaultMutableTreeNode current = new DefaultMutableTreeNode(tagName);

    base.add(current);

    base = current;

    for (int i = 0; i < attr.getLength(); i++) {

        DefaultMutableTreeNode currentAtt = new DefaultMutableTreeNode(attr.getLocalName(i) + " = "+ attr.getValue(i));

        base.add(currentAtt);

    }

}

// error handling for entity parsing if not caught

public void skippedEntity(String name) throws SAXException {

    System.out.println("Skipped Entity: '" + name + "'");

}

// Initial view of Jtree model idle //

@Override

public void startDocument() throws SAXException {

    super.startDocument();

    base = new DefaultMutableTreeNode("XML Viewer");

    ((DefaultTreeModel) xmlJTree.getModel()).setRoot(base);

}

// Adding Description to each subsequent child node //

public void characters(char[] ch, int start, int length) throws SAXException {

    String s = new String(ch, start, length).trim();

    if (!s.equals("")) {

        DefaultMutableTreeNode current = new DefaultMutableTreeNode("Description : " + s);

        base.add(current);

    }

}

// End of current child node branching stopping at parent //

public void endElement(String namespaceURI, String localName, String qName) throws SAXException {

    base = (DefaultMutableTreeNode) base.getParent();

}

// Main Program Start //

public static void main(String[] args) {

    treeViewer = new XMLTreeViewer();

    // treeViewer.xmlSetUp();

    treeViewer.createUI();

}

// Ends current XML file parsing and reloads //

@Override

public void endDocument() throws SAXException {

    // Refresh JTree

    ((DefaultTreeModel) xmlJTree.getModel()).reload();

    //Comment this out if you want the trees to be closed by defaul

    //expandAll(xmlJTree);

}

// Expansion of Jtree structure levels //

public void expandAll(JTree tree) {

    int row = 0;

    while (row < tree.getRowCount()) {

        tree.expandRow(row);

        row++;

    }

}

// Parser takes in current XML file to parse //

public void xmlSetUp(File xmlFile) {

    try {

        /*

        ---------- FOR DOM PARSER -------------

        //Get Document Builder

        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();

        DocumentBuilder builder = factory.newDocumentBuilder();

        //Build Document

        Document document = builder.parse(new File( xmlFile ));

        //Normalize the XML Structure;

        document.getDocumentElement().normalize();

        //Here comes the root node

        Element root = document.getDocumentElement();

        */

        SAXParserFactory fact = SAXParserFactory.newInstance();

        SAXParser parser = fact.newSAXParser();

        parser.parse(xmlFile, this);

    } catch (Exception e) {

        }

    }

// Jtree View component //

public void createUI() {

    treeModel = new DefaultTreeModel(base);

    xmlJTree = new JTree(treeModel);

    JScrollPane scrollPane = new JScrollPane(xmlJTree);

    JFrame windows = new JFrame();

    windows.setTitle("XML file JTree Viewer using SAX Parser");

    JPanel pnl = new JPanel();

    pnl.setLayout(null);

    JLabel lbl = new JLabel("File :");

    txtFile = new JTextField("Selected File Name Here");

    JButton btn = new JButton("Import File");

    btn.addActionListener(new ActionListener() {

        // JFile Chooser is opened after JButton interaction //

        @Override

        public void actionPerformed(ActionEvent evt) {

            JFileChooser fileopen = new JFileChooser();

            FileFilter filter = new FileNameExtensionFilter("xml files", "xml");

            fileopen.addChoosableFileFilter(filter);

            int ret = fileopen.showDialog(null, "Open file");

            if (ret == JFileChooser.APPROVE_OPTION) {

                File file = fileopen.getSelectedFile();

                txtFile.setText(file.getPath() + File.separator + file.getName());

                xmlSetUp(file);

            }

        }

    });

    // Pane window size and interaction //

    lbl.setBounds(0, 0, 100, 30);

    txtFile.setBounds(110, 0, 250, 30);

    btn.setBounds(360, 0, 100, 30);

    scrollPane.setBounds(0, 50, 500, 600);

    pnl.add(lbl);

    pnl.add(txtFile);

    pnl.add(btn);

    pnl.add(scrollPane);

    windows.add(pnl);

    windows.setSize(500, 700);

    windows.setVisible(true);

    windows.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);

}

}