import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;
import org.xml.sax.helpers.DefaultHandler;
import org.xml.sax.SAXParseException;


/**
 * Lecture 8's demonstration of validation.
 *
 * @author  Computer Science E-259
 **/

public class SAXValidator extends DefaultHandler
{
    /**
     * Main driver.  Expects one command-line argument: the name of the 
     * XML file to validate
     *
     * @param argv [0] - filename
     */

    public static void main(String [] argv)
    {
        // grab filename
        String input = argv[0];

        try 
        {
            // instantiate a SAX parser factory
            SAXParserFactory factory = SAXParserFactory.newInstance();

            // enable validation
            factory.setValidating(true);

            // instantiate a SAX parser 
            SAXParser parser = factory.newSAXParser();

            // instantiate our little handler
            SAXValidator handler = new SAXValidator();

            // parse the file
            parser.parse(input, handler);
        } 
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }


    /**
     * Receive notification of a recoverable parser error. 
     *
     * @param e  the exception thrown
     */

    public void error(SAXParseException e) 
    {
        System.out.println("Parsing error at " + e.getLineNumber() + 
                           ":" + e.getColumnNumber() + 
                           ": " + e.getMessage());
    }


    /**
     * Receive notification of a parser warning.
     *
     * @param e  the exception thrown
     */

    public void warning(SAXParseException e) 
    {
        System.out.println("Parsing warning at " + e.getLineNumber() + 
                           ":" + e.getColumnNumber() + 
                           ": " + e.getMessage());
    }


    /**
     * Report a fatal XML parsing error. 
     *
     * @param e  the exception thrown
     */

    public void fatalError(SAXParseException e) 
    {
        System.out.println("Fatal parsing warning at " + e.getLineNumber() +
                           ":" + e.getColumnNumber() + 
                           ": " + e.getMessage());
    }
}