// Sample Java program using SAX to validate, and output to the screen,
// the contents of an XML file.
//
// Coded by Norman Jacobson, May 2007
// 	-- with much referencing to the Java SAX Tutorial,
//  java.sun.com/webservices/jaxp/dist/1.1/docs/tutorial/sax/index.html

// Usage: via command line, issue "java XMLtoScreen <XML file name>"

// Imports:
// Use System.out() to print contents of XML file to screen
import java.io.*;

// Make interfaces for SAX available
import org.xml.sax.*;

// SAX is event-driven: when particular tokens are seen, the
// appropriate event is triggered. DefaultHandler has empty
// methods for all events; we'll overload the ones we need to use
import org.xml.sax.helpers.DefaultHandler;

// Provides class to produce a SAX parser--in Java terms, a parser factory
import javax.xml.parsers.SAXParserFactory;

// ParserConfigurationException is thrown if a parser of the requested type
// cannot be provided
import javax.xml.parsers.ParserConfigurationException;

// What the facory returns to do the parsing
import javax.xml.parsers.SAXParser;


// XMLtoScreen provides appropriate methods to handle
// SAX events generated while parsing the XML file
public class XMLtoScreen extends DefaultHandler
{
	// No indentation at start
	private int numberOfTabStops = 0;

	// Name of XML file to process
	private static String XMLFileName;

	// accept XML file name; print out contents and
	// an error message for each validation error encountered
	public static void main (String[] args)
	{
		// Process command line; if ill-formed, exit
      	if (args.length != 1)
      	{
			System.out.println("Usage: java XMLtoScreen <XML file name>");
			System.exit(1);
     	}

		// Process the file
		//
		// "When a start tag or end tag is encountered, the name of the tag is passed as a
		// String to the startElement or endElement method, as appropriate. When a start tag
		// is encountered, any attributes it defines are also passed in an Attributes list.
		// Characters found within the element are passed as an array of characters, along with
		// the number of characters (length) and an offset into the array that points to the first
		// character."
		// [Java SAX tutorial, java.sun.com/webservices/jaxp/dist/1.1/docs/tutorial/sax/2a_echo.html]

		// Set up a parser factory that validates the XML file as it's processed
    	SAXParserFactory factory = SAXParserFactory.newInstance();
		factory.setValidating(true);

		SAXParser parser = null;
        try
        {
        	// Make a SAX parser
            parser = factory.newSAXParser();
		}
		catch (ParserConfigurationException e)
		{
			System.out.println("\nUnable to make a parse with given configuration!");
			System.exit(1);
		}
		catch (SAXException e)
		{
			System.out.println("\nUnable to create parser factory!");
			System.exit(1);
		}

		// Tell parser the file to process -- it's the one on the command line --
		// and the event handler methods to use -- they are in this class
		XMLFileName = args[0].trim();
		try
		{
            parser.parse(new File(XMLFileName), new XMLtoScreen());
        }
        catch (IOException e)
        {
			System.out.println("\nCould not initialize parser!");
			System.exit(1);
		}

		// We'll get here unless there is a parsing error --
		// and if there is, we want serious info about it
        catch (SAXParseException e)
        {
         	System.out.println("\nParsing error!\n" +
                         	   "  line = " + e.getLineNumber() + "\n" +
                    	       "  location = " + e.getSystemId());
            System.out.println("  " + e.getMessage());
        }

		// We'll get here if there is something else wrong
        catch (SAXException e)
        {
            System.out.println("SAX error: " + e);
        }

	}


	// Event handling routines


	// At start of document, note we've begun
	public void startDocument()
	throws SAXException
	{
		System.out.print("\n\n** Validating and printing " +
		                   XMLFileName + " **\n\n");
	}


	// At end of document, note we're done
	public void endDocument()
	throws SAXException
	{
		System.out.println("\n** Done! **");
	}


	// At the start of an element, indent, print that element as a label for the line
    public void startElement(String namespaceURI,	//namespace (we don't use)
                             String sName, // simple name (localName)
                             String qName, // qualified name
                             Attributes attrs)	//attribute list
    throws SAXException
    {
    	// The name may or may not be qualified; use whichever is present
    	String elementName = sName;
    	if (elementName.equals(""))
    		elementName = qName;

    	System.out.println();
    	++numberOfTabStops;
     	indent(numberOfTabStops);
   		System.out.print(elementName.toUpperCase().trim()  + ": ");

    	// if attributes are present, get their names and list them
    	// indent each new list
        if (attrs != null)
        {
    		++numberOfTabStops;
    		System.out.println();
        	for (int i = 0; i < attrs.getLength(); i++)
        	{
        		// get its local or qualified name, whichever is present
                String attributeName = attrs.getLocalName(i);
                if (attributeName.equals(""))
                	attributeName = attrs.getQName(i);

                indent(numberOfTabStops);
                System.out.print("--> " + attributeName.toLowerCase().trim() + ": ");
                System.out.println(attrs.getValue(i).trim());
   			}
  			--numberOfTabStops;
		}
	}

	// At the end of an element, end the line, back off indentation
	public void endElement(String namespaceURI,	//namespace (we're not using)
	                         String sName, // simple name (localName)
	                         String qName) // qualified name
	throws SAXException
	{
		System.out.println();
		--numberOfTabStops;
	}


	// Write out the characters, if any, between the XML tags
	    public void characters(char buf[], int offset, int len)
    throws SAXException
    {

		String thisCharacterGroup = new String(buf, offset, len).trim();
		if (!thisCharacterGroup.equals(""))
		{
			++numberOfTabStops;
			indent(numberOfTabStops);
       	 	System.out.print(">" + thisCharacterGroup + "<");
       		--numberOfTabStops;
		}
    }


    // Indent given number of 'tab' stops
    // (used to make output a bit prettier)
	private void indent(int numberOfTabStops)
	{
		for (int i = 1; i <= numberOfTabStops; i++)
			System.out.print("    ");		// indent is 4 spaces
	}


}