Create JTree out of XML document in Java

// This is an XML book - no need for explicit Swing imports
import java.awt.BorderLayout;
import java.io.IOException;
import java.io.StringReader;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
//w  ww  .  ja va  2 s .com
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
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.ContentHandler;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.XMLReader;

public class Main{

  /**
   * <p> Static entry point for running the viewer. </p>
   */
  public static void main(String[] args)throws Exception {
         SAXTreeValidator viewer = new SAXTreeValidator();
         viewer.init();
         viewer.setVisible(true);
  }
}

/**
 * <b><code>SAXTreeValidator</code></b> uses Swing to graphically
 *   display an XML document, and performs validation.
 */
class SAXTreeValidator extends JFrame {
    private JTree jTree;

    /** Tree model to use */
    DefaultTreeModel defaultTreeModel;

    /**
     * <p> This initializes the needed Swing settings. </p>
     */
    public SAXTreeValidator() {
        // Handle Swing setup
        super("SAX Tree Validator");
        setSize(600, 450);
    }

    /**
     * <p> This will construct the tree using Swing. </p>
     *
     * @param filename <code>String</code> path to XML document.
     */
    public void init() throws Exception, SAXException {
        DefaultMutableTreeNode base = new DefaultMutableTreeNode("XML Document: ");
        
        // Build the tree model
        defaultTreeModel = new DefaultTreeModel(base);
        jTree = new JTree(defaultTreeModel);

        // Construct the tree hierarchy
        buildTree(defaultTreeModel, base);

        // Display the results
        getContentPane().add(new JScrollPane(jTree), BorderLayout.CENTER);
    }

    /**
     * <p>This handles building the Swing UI tree.</p>
     *
     * @param treeModel Swing component to build upon.
     * @param base tree node to build on.
     * @param xmlURI URI to build XML document from.
     * @throws <code>IOException</code> - when reading the XML URI fails.
     * @throws <code>SAXException</code> - when errors in parsing occur.
     */
    public void buildTree(DefaultTreeModel treeModel, 
                          DefaultMutableTreeNode base) 
        throws Exception, SAXException {

      SAXParserFactory spf = SAXParserFactory.newInstance();
      XMLReader reader = null;
      SAXParser parser = spf.newSAXParser();
      reader = parser.getXMLReader();
      ContentHandler jTreeContentHandler = new JValidatorContentHandler(treeModel, base);
      reader.setContentHandler(jTreeContentHandler);
      StringReader sr = new StringReader("<tag>asdf</tag>");
      //InputSource is = new InputSource("xmlFileName.xml");
      InputSource is = new InputSource(sr);
      reader.parse(is);
    }
}

/**
 * <b><code>JValidatorContentHandler</code></b> implements the SAX
 *   <code>ContentHandler</code> interface and defines callback
 *   behavior for the SAX callbacks associated with an XML
 *   document's content, bulding up JTree nodes.
 */
class JValidatorContentHandler implements ContentHandler {

    /** Hold onto the locator for location information */
    private Locator locator;

    /** Store URI to prefix mappings */
    private Map namespaceMappings;

    /** Tree Model to add nodes to */
    private DefaultTreeModel treeModel;

    /** Current node to add sub-nodes to */
    private DefaultMutableTreeNode current;

    /**
     * <p> Set up for working with the JTree. </p>
     *
     * @param treeModel tree to add nodes to.
     * @param base node to start adding sub-nodes to.
     */
    public JValidatorContentHandler(DefaultTreeModel treeModel, 
                               DefaultMutableTreeNode base) {
        this.treeModel = treeModel;
        this.current = base;
        this.namespaceMappings = new HashMap();
    }

    /**
     * <p>
     *  Provide reference to <code>Locator</code> which provides
     *    information about where in a document callbacks occur.
     * </p>
     *
     * @param locator <code>Locator</code> object tied to callback
     *        process
     */
    public void setDocumentLocator(Locator locator) {
        // Save this for later use
        this.locator = locator;
    }

    /**
     * <p>
     *  This indicates the start of a Document parse-this precedes
     *    all callbacks in all SAX Handlers with the sole exception
     *    of <code>{@link #setDocumentLocator}</code>.
     * </p>
     *
     * @throws <code>SAXException</code> when things go wrong
     */
    public void startDocument() throws SAXException {
        // No visual events occur here
    }

    /**
     * <p>
     *  This indicates the end of a Document parse-this occurs after
     *    all callbacks in all SAX Handlers.</code>.
     * </p>
     *
     * @throws <code>SAXException</code> when things go wrong
     */
    public void endDocument() throws SAXException {
        // No visual events occur here
    }

    /**
     * <p>
     *   This indicates that a processing instruction (other than
     *     the XML declaration) has been encountered.
     * </p>
     *
     * @param target <code>String</code> target of PI
     * @param data <code>String</code containing all data sent to the PI.
     *               This typically looks like one or more attribute value
     *               pairs.
     * @throws <code>SAXException</code> when things go wrong
     */
    public void processingInstruction(String target, String data)
        throws SAXException {

        DefaultMutableTreeNode pi = 
            new DefaultMutableTreeNode("PI (target = '" + target +
                                       "', data = '" + data + "')");
        current.add(pi);
    }

    /**
     * <p>
     *   This indicates the beginning of an XML Namespace prefix
     *     mapping. Although this typically occurs within the root element
     *     of an XML document, it can occur at any point within the
     *     document. Note that a prefix mapping on an element triggers
     *     this callback <i>before</i> the callback for the actual element
     *     itself (<code>{@link #startElement}</code>) occurs.
     * </p>
     *
     * @param prefix <code>String</code> prefix used for the namespace
     *                being reported
     * @param uri <code>String</code> URI for the namespace
     *               being reported
     * @throws <code>SAXException</code> when things go wrong
     */
    public void startPrefixMapping(String prefix, String uri) {
        // No visual events occur here.
        namespaceMappings.put(uri, prefix);
    }

    /**
     * <p>
     *   This indicates the end of a prefix mapping, when the namespace
     *     reported in a <code>{@link #startPrefixMapping}</code> callback
     *     is no longer available.
     * </p>
     *
     * @param prefix <code>String</code> of namespace being reported
     * @throws <code>SAXException</code> when things go wrong
     */
    public void endPrefixMapping(String prefix) {
        // No visual events occur here.
        for (Iterator i = namespaceMappings.keySet().iterator(); 
             i.hasNext(); ) {

            String uri = (String)i.next();
            String thisPrefix = (String)namespaceMappings.get(uri);
            if (prefix.equals(thisPrefix)) {
                namespaceMappings.remove(uri);
                break;
            }
        }
    }

    /**
     * <p>
     *   This reports the occurrence of an actual element. It includes
     *     the element's attributes, with the exception of XML vocabulary
     *     specific attributes, such as
     *     <code>xmlns:[namespace prefix]</code> and
     *     <code>xsi:schemaLocation</code>.
     * </p>
     *
     * @param namespaceURI <code>String</code> namespace URI this element
     *               is associated with, or an empty <code>String</code>
     * @param localName <code>String</code> name of element (with no
     *               namespace prefix, if one is present)
     * @param qName <code>String</code> XML 1.0 version of element name:
     *                [namespace prefix]:[localName]
     * @param atts <code>Attributes</code> list for this element
     * @throws <code>SAXException</code> when things go wrong
     */
    public void startElement(String namespaceURI, String localName,
                             String qName, Attributes atts)
        throws SAXException {

        DefaultMutableTreeNode element = 
            new DefaultMutableTreeNode("Element: " + localName);
        current.add(element);
        current = element;

        // Determine namespace
        if (namespaceURI.length() > 0) {
            String prefix = 
                (String)namespaceMappings.get(namespaceURI);
            if (prefix.equals("")) {
                prefix = "[None]";
            }
            DefaultMutableTreeNode namespace =
                new DefaultMutableTreeNode("Namespace: prefix = '" +
                    prefix + "', URI = '" + namespaceURI + "'");
            current.add(namespace);
        }

        // Process attributes
        for (int i=0; i<atts.getLength(); i++) {
            DefaultMutableTreeNode attribute =
                new DefaultMutableTreeNode("Attribute (name = '" +
                                           atts.getLocalName(i) + 
                                           "', value = '" +
                                           atts.getValue(i) + "')");
            String attURI = atts.getURI(i);
            if (attURI.length() > 0) {
                String attPrefix = 
                    (String)namespaceMappings.get(namespaceURI);
                if (attPrefix.equals("")) {
                    attPrefix = "[None]";
                }
                DefaultMutableTreeNode attNamespace =
                    new DefaultMutableTreeNode("Namespace: prefix = '" +
                        attPrefix + "', URI = '" + attURI + "'");
                attribute.add(attNamespace);            
            }
            current.add(attribute);
        }
    }

    /**
     * <p>
     *   Indicates the end of an element
     *     (<code>&lt;/[element name]&gt;</code>) is reached. Note that
     *     the parser does not distinguish between empty
     *     elements and non-empty elements, so this occurs uniformly.
     * </p>
     *
     * @param namespaceURI <code>String</code> URI of namespace this
     *                element is associated with
     * @param localName <code>String</code> name of element without prefix
     * @param qName <code>String</code> name of element in XML 1.0 form
     * @throws <code>SAXException</code> when things go wrong
     */
    public void endElement(String namespaceURI, String localName,
                           String qName)
        throws SAXException {

        // Walk back up the tree
        current = (DefaultMutableTreeNode)current.getParent();
    }

    /**
     * <p>
     *   This reports character data (within an element).
     * </p>
     *
     * @param ch <code>char[]</code> character array with character data
     * @param start <code>int</code> index in array where data starts.
     * @param length <code>int</code> index in array where data ends.
     * @throws <code>SAXException</code> when things go wrong
     */
    public void characters(char[] ch, int start, int length)
        throws SAXException {

        String s = new String(ch, start, length);
        DefaultMutableTreeNode data =
            new DefaultMutableTreeNode("Character Data: '" + s + "'");
        current.add(data);
    }

    /**
     * <p>
     * This reports whitespace that can be ignored in the
     * originating document. This is typically invoked only when
     * validation is ocurring in the parsing process.
     * </p>
     *
     * @param ch <code>char[]</code> character array with character data
     * @param start <code>int</code> index in array where data starts.
     * @param end <code>int</code> index in array where data ends.
     * @throws <code>SAXException</code> when things go wrong
     */
    public void ignorableWhitespace(char[] ch, int start, int length)
        throws SAXException {
        
        // This is ignorable, so don't display it
    }

    /**
     * <p>
     *   This reports an entity that is skipped by the parser. This
     *     should only occur for non-validating parsers, and then is still
     *     implementation-dependent behavior.
     * </p>
     *
     * @param name <code>String</code> name of entity being skipped
     * @throws <code>SAXException</code> when things go wrong
     */
    public void skippedEntity(String name) throws SAXException {
        DefaultMutableTreeNode skipped =
            new DefaultMutableTreeNode("Skipped Entity: '" + name + "'");
        current.add(skipped);
    }
}

/**
 * <b><code>JValidatorErrorHandler</code></b> implements the SAX
 *   <code>ErrorHandler</code> interface and defines callback
 *   behavior for the SAX callbacks associated with an XML
 *   document's warnings and errors.
 */
class JValidatorErrorHandler implements ErrorHandler {

    /**
     * <p>
     * This will report a warning that has occurred; this indicates
     *   that while no XML rules were "broken", something appears
     *   to be incorrect or missing.
     * </p>
     *
     * @param exception <code>SAXParseException</code> that occurred.
     * @throws <code>SAXException</code> when things go wrong 
     */
    public void warning(SAXParseException exception)
        throws SAXException {
            
        System.out.println("**Parsing Warning**\n" +
                           "  Line:    " + 
                              exception.getLineNumber() + "\n" +
                           "  URI:     " + 
                              exception.getSystemId() + "\n" +
                           "  Message: " + 
                              exception.getMessage());        
        throw new SAXException("Warning encountered");
    }

    /**
     * <p>
     * This will report an error that has occurred; this indicates
     *   that a rule was broken, typically in validation, but that
     *   parsing can reasonably continue.
     * </p>
     *
     * @param exception <code>SAXParseException</code> that occurred.
     * @throws <code>SAXException</code> when things go wrong 
     */
    public void error(SAXParseException exception)
        throws SAXException {
        
        System.out.println("**Parsing Error**\n" +
                           "  Line:    " + 
                              exception.getLineNumber() + "\n" +
                           "  URI:     " + 
                              exception.getSystemId() + "\n" +
                           "  Message: " + 
                              exception.getMessage());
        throw new SAXException("Error encountered");
    }

    /**
     * <p>
     * This will report a fatal error that has occurred; this indicates
     *   that a rule has been broken that makes continued parsing either
     *   impossible or an almost certain waste of time.
     * </p>
     *
     * @param exception <code>SAXParseException</code> that occurred.
     * @throws <code>SAXException</code> when things go wrong 
     */
    public void fatalError(SAXParseException exception)
        throws SAXException {
    
        System.out.println("**Parsing Fatal Error**\n" +
                           "  Line:    " + 
                              exception.getLineNumber() + "\n" +
                           "  URI:     " + 
                              exception.getSystemId() + "\n" +
                           "  Message: " + 
                              exception.getMessage());        
        throw new SAXException("Fatal Error encountered");
    }
}
/*-- 

Copyright (C) 2001 Brett McLaughlin.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:

1. Redistributions of source code must retain the above copyright
   notice, this list of conditions, and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions, and the disclaimer that follows 
   these conditions in the documentation and/or other materials 
   provided with the distribution.

3. The name "Java and XML" must not be used to endorse or promote products
   derived from this software without prior written permission.  For
   written permission, please contact brett@newInstance.com.

In addition, we request (but do not require) that you include in the 
end-user documentation provided with the redistribution and/or in the 
software itself an acknowledgement equivalent to the following:
    "This product includes software developed for the
     'Java and XML' book, by Brett McLaughlin (O'Reilly & Associates)."

THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED.  IN NO EVENT SHALL THE JDOM AUTHORS OR THE PROJECT
CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.

*/