Implement SAX parser content handler in Java

import java.io.StringReader;
/*w ww  . j  a  va 2  s . co  m*/
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 {
  public static void main(String args[]) throws Exception {
    SAXParserFactory spf = SAXParserFactory.newInstance();
    XMLReader reader = null;
    SAXParser parser = spf.newSAXParser();
    reader = parser.getXMLReader();
    reader.setErrorHandler(new MyErrorHandler());
    reader.setContentHandler(new MyContentHandler());
    
    StringReader sr = new StringReader("<tag></tag>");
    
    
    //InputSource is = new InputSource("xmlFileName.xml");
    InputSource is = new InputSource(sr);
    reader.parse(is);
  }
}
class MyErrorHandler implements ErrorHandler {
  public void warning(SAXParseException e) throws SAXException {
    show("Warning", e);
    throw (e);
  }

  public void error(SAXParseException e) throws SAXException {
    show("Error", e);
    throw (e);
  }

  public void fatalError(SAXParseException e) throws SAXException {
    show("Fatal Error", e);
    throw (e);
  }

  private void show(String type, SAXParseException e) {
    System.out.println(type + ": " + e.getMessage());
    System.out.println("Line " + e.getLineNumber() + " Column " + e.getColumnNumber());
    System.out.println("System ID: " + e.getSystemId());
  }
}
class MyContentHandler implements ContentHandler {
  private Locator locator;

  public void setDocumentLocator(Locator locator) {
    this.locator = locator;
    System.out.println("-" + locator.getLineNumber() + "---Document ID: " + locator.getSystemId());
  }

  public void startDocument() {
    System.out.println("-" + locator.getLineNumber() + "---Document parse started");
  }

  public void endDocument() {
    System.out.println("-" + locator.getLineNumber() + "---Document parse ended");
  }

  public void startPrefixMapping(String prefix, String uri) {
    System.out.println("-" + locator.getLineNumber() + "---Namespace scope begins");
    System.out.println("     " + prefix + "=\"" + uri + "\"");
  }

  public void endPrefixMapping(String prefix) {
    System.out.println("-" + locator.getLineNumber() + "---Namespace scope ends");
    System.out.println("     " + prefix);
  }

  public void startElement(String namespaceURI, String localName, String qName, Attributes atts) {
    System.out.println("-" + locator.getLineNumber() + "---Opening tag of an element");
    System.out.println("       Namespace: " + namespaceURI);
    System.out.println("      Local name: " + localName);
    System.out.println("  Qualified name: " + qName);
    for (int i = 0; i < atts.getLength(); i++) {
      System.out.println("       Attribute: " + atts.getQName(i) + "=\"" + atts.getValue(i) + "\"");
    }
  }

  public void endElement(String namespaceURI, String localName, String qName) {
    System.out.println("-" + locator.getLineNumber() + "---Closing tag of an element");
    System.out.println("       Namespace: " + namespaceURI);
    System.out.println("      Local name: " + localName);
    System.out.println("  Qualified name: " + qName);
  }

  public void characters(char[] ch, int start, int length) {
    System.out.println("-" + locator.getLineNumber() + "---Character data");
    showCharacters(ch, start, length);
  }

  public void ignorableWhitespace(char[] ch, int start, int length) {
    System.out.println("-" + locator.getLineNumber() + "---Whitespace");
    showCharacters(ch, start, length);
  }

  public void processingInstruction(String target, String data) {
    System.out.println("-" + locator.getLineNumber() + "---Processing Instruction");
    System.out.println("         Target: " + target);
    System.out.println("           Data: " + data);
  }

  public void skippedEntity(String name) {
    System.out.println("-" + locator.getLineNumber() + "---Skipped Entity");
    System.out.println("           Name: " + name);
  }

  public void showCharacters(char[] ch, int start, int length) {
    System.out.print("        \"");
    for (int i = start; i < start + length; i++)
      switch (ch[i]) {
      case '\n':
        System.out.print("\\n");
        break;
      case '\r':
        System.out.print("\\r");
        break;
      case '\t':
        System.out.print("\\t");
        break;
      default:
        System.out.print(ch[i]);
        break;
      }
    System.out.println("\"");
  }
}