MyDOM.java

/* Parser skeleton for processing item-???.xml files. Must be compiled in
 * JDK 1.5 or above.
 *
 * Instructions:
 *
 * This program processes all files passed on the command line (to parse
 * an entire diectory, type "java MyParser myFiles/*.xml" at the shell).
 *
 */

import java.io.*;
import java.text.*;
import java.util.*;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.FactoryConfigurationError;
import javax.xml.parsers.ParserConfigurationException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
// import org.w3c.dom.Element;
// import org.w3c.dom.Text;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.ErrorHandler;

class MyDOM {

    static final String columnSeparator = "|*|";
    static DocumentBuilder builder;

    static final String[] typeName = {
            "none",
            "Element",
            "Attr",
            "Text",
            "CDATA",
            "EntityRef",
            "Entity",
            "ProcInstr",
            "Comment",
            "Document",
            "DocType",
            "DocFragment",
            "Notation",
    };

    static class MyErrorHandler implements ErrorHandler {

        public void warning(SAXParseException exception)
                throws SAXException {
            fatalError(exception);
        }

        public void error(SAXParseException exception)
                throws SAXException {
            fatalError(exception);
        }

        public void fatalError(SAXParseException exception)
                throws SAXException {
            exception.printStackTrace();
            System.out.println("There should be no errors " +
                    "in the supplied XML files.");
            System.exit(3);
        }

    }

    /*
     * Returns the amount (in XXXXX.xx format) denoted by a money-string
     * like $3,453.23. Returns the input if the input is an empty string.
     */
    static String strip(String money) {
        if (money.equals(""))
            return money;
        else {
            double am = 0.0;
            NumberFormat nf = NumberFormat.getCurrencyInstance(Locale.US);
            try {
                am = nf.parse(money).doubleValue();
            } catch (ParseException e) {
                System.out.println("This method should work for all " +
                        "money values you find in our data.");
                System.exit(20);
            }
            nf.setGroupingUsed(false);
            return nf.format(am).substring(1);
        }
    }

    /*
     * Process one items-???.xml file.
     */
    static void processFile(File xmlFile) {
        Document doc = null;
        try {
            doc = builder.parse(xmlFile);
        } catch (IOException e) {
            e.printStackTrace();
            System.exit(3);
        } catch (SAXException e) {
            System.out.println("Parsing error on file " + xmlFile);
            System.out.println("  (not supposed to happen with supplied XML files)");
            e.printStackTrace();
            System.exit(3);
        }

        /*
         * At this point 'doc' contains a DOM representation of an 'Items' XML
         * file. Use doc.getDocumentElement() to get the root Element.
         */
        System.out.println("Successfully parsed - " + xmlFile);

        /*
         * Fill in code here (you will probably need to write auxiliary
         * methods).
         */

        /**************************************************************/

        recursiveDescent(doc, 0);
    }

    public static void recursiveDescent(Node n, int level) {
        // adjust indentation according to level
        for (int i = 0; i < 4 * level; i++)
            System.out.print(" ");

        // dump out node name, type, and value
        String ntype = typeName[n.getNodeType()];
        String nname = n.getNodeName();
        String nvalue = n.getNodeValue();

        System.out.println("Type = " + ntype + ", Name = " + nname + ", Value = " + nvalue);

        // dump out attributes if any
        org.w3c.dom.NamedNodeMap nattrib = n.getAttributes();
        if (nattrib != null && nattrib.getLength() > 0)
            for (int i = 0; i < nattrib.getLength(); i++)
                recursiveDescent(nattrib.item(i), level + 1);

        // now walk through its children list
        org.w3c.dom.NodeList nlist = n.getChildNodes();

        for (int i = 0; i < nlist.getLength(); i++)
            recursiveDescent(nlist.item(i), level + 1);
    }

    public static void main(String[] args) {
        if (args.length == 0) {
            System.out.println("Usage: java MyParser [file] [file] ...");
            System.exit(1);
        }

        /* Initialize parser. */
        try {
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            factory.setValidating(false);
            factory.setIgnoringElementContentWhitespace(true);
            builder = factory.newDocumentBuilder();
            builder.setErrorHandler(new MyErrorHandler());
        } catch (FactoryConfigurationError e) {
            System.out.println("unable to get a document builder factory");
            System.exit(2);
        } catch (ParserConfigurationException e) {
            System.out.println("parser was unable to be configured");
            System.exit(2);
        }

        /* Process all files listed on command line. */
        for (int i = 0; i < args.length; i++) {
            File currentFile = new File(args[i]);
            processFile(currentFile);
        }
    }
}