import javax.xml.parsers.*;
import org.xml.sax.*;
import org.xml.sax.helpers.*;

/** A program using SAX to keep track of the number
 *  of copies of Core Web Programming ordered. Entries
 *  that look like this will be recorded:<XMP>
 *    ...
 *    <count>23</count>
 *    <book>
 *      <isbn>0130897930</isbn>
 *      ...
 *    </book>
 *  
 *  </XMP>All other entries will be ignored -- different books,
 *  orders for yachts, things that are not even orders, etc.
 *
 *  Taken from Core Web Programming from 
 *  Prentice Hall and Sun Microsystems Press,
 *  http://www.corewebprogramming.com/.
 *  &copy; 2001 Marty Hall and Larry Brown;
 *  may be freely used or adapted. 
 */

public class CountBooks {
  public static void main(String[] args) {
    String jaxpPropertyName =
      "javax.xml.parsers.SAXParserFactory";
    // Pass the parser factory in on the command line with
    // -D to override the use of the Apache parser.
    if (System.getProperty(jaxpPropertyName) == null) {
      String apacheXercesPropertyValue =
        "org.apache.xerces.jaxp.SAXParserFactoryImpl";
      System.setProperty(jaxpPropertyName,
                         apacheXercesPropertyValue);
    }
    String filename;
    if (args.length > 0) {
      filename = args[0];
    } else {
      String[] extensions = { "xml" };
      WindowUtilities.setNativeLookAndFeel();
      filename = ExtensionFileFilter.getFileName(".",
                                                 "XML Files",
                                                 extensions);
      if (filename == null) {
        filename = "orders.xml";
      }
    }
    countBooks(filename);
    System.exit(0);
  }

  private static void countBooks(String filename) {
    DefaultHandler handler = new CountHandler();
    SAXParserFactory factory = SAXParserFactory.newInstance();
    try {
      SAXParser parser = factory.newSAXParser();
      parser.parse(filename, handler);
    } catch(Exception e) {
      String errorMessage =
        "Error parsing " + filename + ": " + e;
      System.err.println(errorMessage);
      e.printStackTrace();
    }
  }
}