/*
    * $Id: XmlOutputServlet.java 126 2004-11-01 20:30:33Z josem $
    *
    * Tarsis
    * Copyright (C) 2002 Talika Open Source Group
    *
    * This program is free software; you can redistribute it and/or modify
    * it under the terms of the GNU General Public License as published by
    * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   *
   */
  
  package org.talika.tarsis.servlets;
  
  import java.io.PrintWriter;
  import java.util.Collection;
  import java.util.Enumeration;
  import java.util.Iterator;
  
  import javax.servlet.ServletConfig;
  import javax.servlet.ServletException;
  import javax.servlet.http.HttpServletRequest;
  import javax.servlet.http.HttpServletResponse;
  
  import org.talika.commons.util.FormatHelper;
  
  /**
   * XML output servlet of Tarsis MVC Framework.<br>
   * <br>
   *
   * @author  Jose M. Palomar
   * @version $Revision: 126 $
   */
  public final class XmlOutputServlet extends AbstractServlet {
  
      // Constants
      /**
       * Content type.
       */
      private static final String CONTENT_TYPE = "text/xml";
  
      /**
       * XML doc type.
       */
      private static final String DOC_TYPE =
                  "<!DOCTYPE xml-output\n" +
                      "\tPUBLIC \"-//Talika Open Source Group//Xml Output DTD 1.0//ES\"\n" +
                      "\t\"http://www.talika.org/dtds/xml-output_1_0.dtd\">\n";
  
      // Fields
      /**
       * Format helper instance.
       */
      private FormatHelper formatHelper;
  
      // Methods
      /**
       * Called by the servlet container to indicate to a servlet that the servlet is
       * being placed into service.<br>
       * <br>
       *
       * @param config ServletConfig the <code>ServletConfig</code> object that contains
       * configutation information for this servlet.
       * @throws ServletException if an exception occurs that interrupts the servlet's
       * normal operation.
       * @see javax.servlet.Servlet#init(ServletConfig)
       */
      public void init(ServletConfig config) throws ServletException {
          super.init(config);
          this.formatHelper = FormatHelper.getInstance();
      }
  
      /**
       * Called by the servlet container to indicate to a servlet that the servlet is
       * being taken out of service.
       *
       * @see javax.servlet.Servlet#destroy()
       */
      public void destroy() {
          super.destroy();
      }
  
      /**
       * Processes requests for both HTTP GET and POST methods.<br>
       * <br>
       *
       * @param request servlet object that contains the request the client has made of
       * the servlet.
       * @param response servlet object that contains the response the servlet sends to
      * the client.
      * @throws ServletException if the request could not be handled.
      * @throws IOException if an input or output error is detected when the servlet
      * handles request.
      */
     protected void process(HttpServletRequest request, HttpServletResponse response)
     throws ServletException, java.io.IOException {
 
         try {
 
             // Set Content Type
             response.setContentType(CONTENT_TYPE);
 
             PrintWriter out = response.getWriter();
 
             // Print Header
             printHeader(out);
 
             Enumeration atts = request.getAttributeNames();
             while (atts.hasMoreElements()) {
 
                 String attName = (String) atts.nextElement();
                 Object attValue = request.getAttribute(attName);
 
                 if (attValue instanceof Collection) {
                     printValueList(out, attName, (Collection) attValue);
                 }
                 else {
                     printValue(out, attName, attValue);
                 }
 
             }
 
             printFooter(out);
 
         }
         catch (Throwable t) {
             throw new ServletException(t);
         }
 
     }
 
     /**
      * Prints document header.
      *
      * @param out PrintWriter writer.
      */
     private void printHeader(PrintWriter out) {
 
         out.println("<?xml version=\"1.0\" encoding=\"UTF-8\" ?>");
         out.println();
         out.println(DOC_TYPE);
         out.println();
 
         out.println("<xml-output>");
 
     }
 
     /**
      * Prints attribute value.
      *
      * @param out PrintWriter writer.
      * @param name String attribute name.
      * @param value Object attribute value.
      */
     private void printValue(PrintWriter out, String name, Object value) {
 
         out.println("\t<attribute>");
         out.println("\t\t<name>" + name + "</name>");
         out.println("\t\t<value>" + formatHelper.formatObject(value) + "</value>");
         out.println("\t</attribute>");
 
     }
 
     /**
      * Prints attribute values.
      *
      * @param out PrintWriter writer.
      * @param name String attribute name.
      * @param values Collection values collection.
      */
     private void printValueList(PrintWriter out, String name, Collection values) {
 
         if (values.isEmpty()) {
             return;
         }
 
         out.println("\t<attribute>");
         out.println("\t\t<name>" + name + "</name>");
         Iterator valuesIterator = values.iterator();
         while (valuesIterator.hasNext()) {
             Object value = valuesIterator.next();
             out.println("\t\t<value>" + formatHelper.formatObject(value) + "</value>");
         }
         out.println("\t</attribute>");
 
     }
 
     /**
      * Prints document footer.
      *
      * @param out PrintWriter writer.
      */
     private void printFooter(PrintWriter out) {
 
         out.println("</xml-output>");
 
     }
 
 }