Servlets and XML: Made for each other

//---------------------------------------------------------------------------||
// xmlfromdom.java                                                           ||
//                                                                           ||
// This code generates an XML document from a portion of a DOM tree.         ||
//---------------------------------------------------------------------------||
// Written 17 February 2000 by Doug Tidwell.                                 ||
//---------------------------------------------------------------------------||
//                                                                           ||
// (C) Copyright IBM Corp. 1999, 2000.  All rights reserved.                 ||
//                                                                           ||
// US Government Users Restricted Rights Use, duplication or                 ||
// disclosure restricted by GSA ADP Schedule Contract with IBM Corp.         ||
//                                                                           ||
// The program is provided "as is" without any warranty express or           ||
// implied, including the warranty of non-infringement and the implied       ||
// warranties of merchantibility and fitness for a particular purpose.       ||
// IBM will not be liable for any damages suffered by you as a result        ||
// of using the Program. In no event will IBM be liable for any              ||
// special, indirect or consequential damages or lost profits even if        ||
// IBM has been advised of the possibility of their occurrence. IBM          ||
// will not be liable for any third party claims against you.                ||
//                                                                           ||
//---------------------------------------------------------------------------||

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.apache.xerces.parsers.*;

public class xmlfromdom extends HttpServlet 
{
  Document doc = null;
  Element author = null;
  Element lines = null;
  Element title = null;
 
  public void initialize()
  {
    try 
      {
        doc = (Document)Class.
          forName("org.apache.xerces.dom.DocumentImpl").
          newInstance();
      }
    catch (ClassNotFoundException cnfe)
      {
        System.err.println(cnfe);
      }
    catch (IllegalAccessException iae)
      {
        System.err.println(iae);
      }
    catch (InstantiationException ie)
      {
        System.err.println(ie);
      }

    if (doc != null)
      {
        Element root = doc.createElement("sonnet");
        root.setAttribute("type", "Shakespearean");
  
        author = doc.createElement("author");
  
        Element lastName = doc.createElement("last-name");
        lastName.appendChild(doc.createTextNode("Shakespeare"));
        author.appendChild(lastName);
  
        Element firstName = doc.createElement("first-name");
        firstName.appendChild(doc.createTextNode("William"));
        author.appendChild(firstName);
  
        Element nationality = doc.createElement("nationality");
        nationality.appendChild(doc.createTextNode("British"));
        author.appendChild(nationality);
  
        Element yearOfBirth = doc.createElement("year-of-birth");
        yearOfBirth.appendChild(doc.createTextNode("1564"));
        author.appendChild(yearOfBirth);
  
        Element yearOfDeath = doc.createElement("year-of-death");
        yearOfDeath.appendChild(doc.createTextNode("1616"));
        author.appendChild(yearOfDeath);
  
        root.appendChild(author);

        title = doc.createElement("title");
        title.appendChild(doc.createTextNode("Sonnet 130"));
        root.appendChild(title);

        lines = doc.createElement("lines");

        Element line01 = doc.createElement("line");
        line01.appendChild(doc.createTextNode("My mistress' eyes are nothing like the sun,"));
        lines.appendChild(line01);

        Element line02 = doc.createElement("line");
        line02.appendChild(doc.createTextNode("Coral is far more red than her lips red."));
        lines.appendChild(line02);

        Element line03 = doc.createElement("line");
        line03.appendChild(doc.createTextNode("If snow be white, why then her breasts are dun,"));
        lines.appendChild(line03);

        Element line04 = doc.createElement("line");
        line04.appendChild(doc.createTextNode("If hairs be wires, black wires grow on her head."));
        lines.appendChild(line04);

        Element line05 = doc.createElement("line");
        line05.appendChild(doc.createTextNode("I have seen roses damasked, red and white,"));
        lines.appendChild(line05);

        Element line06 = doc.createElement("line");
        line06.appendChild(doc.createTextNode("But no such roses see I in her cheeks."));
        lines.appendChild(line06);

        Element line07 = doc.createElement("line");
        line07.appendChild(doc.createTextNode("And in some perfumes is there more delight"));
        lines.appendChild(line07);

        Element line08 = doc.createElement("line");
        line08.appendChild(doc.createTextNode("Than in the breath that from my mistress reeks."));
        lines.appendChild(line08);

        Element line09 = doc.createElement("line");
        line09.appendChild(doc.createTextNode("I love to hear her speak, yet well I know"));
        lines.appendChild(line09);

        Element line10 = doc.createElement("line");
        line10.appendChild(doc.createTextNode("That music hath a far more pleasing sound."));
        lines.appendChild(line10);

        Element line11 = doc.createElement("line");
        line11.appendChild(doc.createTextNode("I grant I never saw a goddess go,"));
        lines.appendChild(line11);

        Element line12 = doc.createElement("line");
        line12.appendChild(doc.createTextNode("My mistress when she walks, treads on the ground."));
        lines.appendChild(line12);

        Element line13 = doc.createElement("line");
        line13.appendChild(doc.createTextNode("And yet, by Heaven, I think my love as rare"));
        lines.appendChild(line13);

        Element line14 = doc.createElement("line");
        line14.appendChild(doc.createTextNode("As any she belied with false compare."));
        lines.appendChild(line14);

        root.appendChild(lines);

        doc.appendChild(root);
      }
  }

  /** Prints the specified node, recursively. */
  public void printDOMTree(Node node, PrintWriter out) 
  {
    int type = node.getNodeType();
    switch (type)
    {
      // print the document element
      case Node.DOCUMENT_NODE: 
        {
          printDOMTree(((Document)node).getDocumentElement(), out);
          break;
        }

        // print element with attributes
      case Node.ELEMENT_NODE: 
        {
          out.print("<");
          out.print(node.getNodeName());
          NamedNodeMap attrs = node.getAttributes();
          for (int i = 0; i < attrs.getLength(); i++)
          {
            Node attr = attrs.item(i);
            out.print(" " + attr.getNodeName() + 
                      "=\"" + attr.getNodeValue() + 
                      "\"");
          }
          out.print(">");

          NodeList children = node.getChildNodes();
          if (children != null)
          {
            int len = children.getLength();
            for (int i = 0; i < len; i++)
              printDOMTree(children.item(i), out);
          }

          break;
        }

        // handle entity reference nodes
      case Node.ENTITY_REFERENCE_NODE: 
        {
          out.print("&");
          out.print(node.getNodeName());
          out.print(";");
          break;
        }

        // print cdata sections
      case Node.CDATA_SECTION_NODE: 
        {
          out.print("<![CDATA[");
          out.print(node.getNodeValue());
          out.print("]]>");
          break;
        }

        // print text
      case Node.TEXT_NODE: 
        {
          out.print(node.getNodeValue());
          break;
        }

        // print processing instruction
      case Node.PROCESSING_INSTRUCTION_NODE: 
        {
          out.print("<?");
          out.print(node.getNodeName());
          String data = node.getNodeValue();
          {
            out.print(" ");
            out.print(data);
          }
          out.print("?>");
          break;
        }
    }

    if (type == Node.ELEMENT_NODE)
    {
      out.print("</");
      out.print(node.getNodeName());
      out.print('>');
    }
  } // printDOMTree(Node, PrintWriter)

  public void service(HttpServletRequest request,
                      HttpServletResponse response)
    throws IOException, ServletException
  {
    if (doc == null)
      initialize();

    response.setContentType("text/xml");
    PrintWriter out = response.getWriter();
    
    Enumeration keys;
    String key;
    String requestedSubtree = "";

    keys = request.getParameterNames();
    while (keys.hasMoreElements())
    {
      key = (String) keys.nextElement();
      if (key.equalsIgnoreCase("subtree"))
        requestedSubtree = request.getParameter(key);
    }

    out.println("<?xml version=\"1.0\" ?>");

    if (requestedSubtree.equalsIgnoreCase("author"))
      printDOMTree(author, out);
    else if (requestedSubtree.equalsIgnoreCase("lines"))
      printDOMTree(lines, out);
    else if (requestedSubtree.equalsIgnoreCase("title"))
      printDOMTree(title, out);
    else 
      printDOMTree(doc, out);
  }
}