/*

  * $Source: /usr/cvsroot/melati/melati/src/main/java/org/melati/servlet/TemplateServlet.java,v $

  * $Revision: 1.53 $

  *

  * Copyright (C) 2000 Tim Joyce

  *

  * Part of Melati (http://melati.org), a framework for the rapid

  * development of clean, maintainable web applications.

  *

  * Melati is free software; Permission is granted to copy, distribute

  * and/or modify this software under the terms either:

  *

  * a) 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,

  *

  *    or

  *

  * b) any version of the Melati Software License, as published

  *    at http://melati.org

  *

  * You should have received a copy of the GNU General Public License and

  * the Melati Software License along with this program;

  * if not, write to the Free Software Foundation, Inc.,

  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA to obtain the

  * GNU General Public License and visit http://melati.org to obtain the

  * Melati Software License.

  *

  * Feel free to contact the Developers of Melati (http://melati.org),

  * if you would like to work out a different arrangement than the options

  * outlined here.  It is our intention to allow Melati to be used by as

  * wide an audience as possible.

  *

  * 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.

  *

  * Contact details for copyright holder:

  *

  *     Tim Joyce <timj At paneris.org>

  *     http://paneris.org/

  *     68 Sandbanks Rd, Poole, Dorset. BH14 8BY. UK

  */

 package org.melati.servlet;

 import java.io.PrintWriter;

 import java.io.StringWriter;

 import javax.servlet.ServletException;

 import javax.servlet.ServletConfig;

 import org.melati.Melati;

 import org.melati.util.MelatiWriter;

 import org.melati.template.ServletTemplateEngine;

 import org.melati.template.ServletTemplateContext;

 import org.melati.template.MultipartTemplateContext;

 import org.melati.template.TemplateEngineException;

 import org.melati.template.Template;

 /**

  * Base class to use Melati with a Template Engine.

  * To create your own servlet simply extend this class, 

  * overriding the <code>doTemplateRequest</code> method.

  *

  * @author Tim Joyce

  * $Revision: 1.53 $

  */

 public abstract class TemplateServlet extends PoemServlet {

   /**

    * Eclipse generated. 

    */

   private static final long serialVersionUID = -5228388231472549208L;

   // the template engine

   protected ServletTemplateEngine templateEngine;

   /**

    * Inititialise the template engine.

    *

    * @param config a <code>ServletConfig</code>

    * @throws ServletException if the ServletTemplateEngine has a problem

    */

   public void init(ServletConfig config) throws ServletException {

     super.init(config);

     try {

       templateEngine = melatiConfig.getServletTemplateEngine();

       templateEngine.init(melatiConfig, this);

     } catch (TemplateEngineException e) {

       // log it to system.err as ServletExceptions go to the

       // servlet runner log (eg jserv.log), and don't have a stack trace!

       e.printStackTrace(System.err);

       throw new ServletException(e.toString());

     }

   }

   /**

    * Set the ServletTemplateEngine and ServletTemplateContext in our Melati.

    * This allows us to parse any uploaded files before we enter

    * our PoemSession (so we don't hang on to transactions

    * unnecessarily).

    *

    * @param melati the current Melati

    * @throws Exception if anything goes wrong

    */

   protected void prePoemSession(Melati melati) throws Exception {

     // for this request, set the Initialised Template Engine

     melati.setTemplateEngine(templateEngine);

     ServletTemplateContext templateContext =

             templateEngine.getServletTemplateContext(melati);

     melati.setTemplateContext(templateContext);

   }

   protected void doPoemRequest(Melati melati) throws Exception {

     ServletTemplateContext templateContext = melati.getServletTemplateContext();

     // If we have an multipart form, we use a different template context

     // which allows us to access the uploaded files as well as fields.

     // This used to be in prePoemSession, but the use case was pretty thin,

     // the main Adaptor is PoemFileFormDataAdaptor, which needs to be in session.

     String contentType = melati.getRequest().getHeader("content-type");

     if (contentType != null && contentType.length() >= 19 &&

         contentType.substring(0,19).equalsIgnoreCase("multipart/form-data")) {

       templateContext =

         new MultipartTemplateContext(melati, templateContext);

     }

     templateContext.put("melati", melati);

     templateContext.put("ml", melati.getMarkupLanguage());

     String templateName = doTemplateRequest(melati,templateContext);

     // only expand a template if we have one (it could be a redirect)

     if (templateName != null) {

       templateName = addExtension(templateName);

       templateEngine.expandTemplate(melati.getWriter(), 

                                     templateName,

                                     templateContext);

     }

   }

   /**

    * The template extension is added in an overridable method

    * to allow the application developer to specify their own template

    * extensions.

    * <p>

    * To obtain nice URLs one method is to call your templates 

    * <code>foo.html.wm</code> for example, your urls can then look like

    * <code>servlet/db/table/troid/method.html</code>.

    */

   protected String addExtension(String templateName) {

     if (!templateName.endsWith(templateEngine.templateExtension()))  

       return templateName + templateEngine.templateExtension();

     else

       return templateName;      

   }

   /**

    * Send an error message.

    * 

    * Single call to the templet loader giving purpose (error) and 

    * Exception class.

    *

    * This will look in the purpose directory, 

    * the standard templet directory and the classpath, in that order, 

    * for a templet.

    * This can no longer fail with NotFoundException, 

    * as the Object templet will always be found 

    * (or this is a broken installation).

    *

    * @param melati the {@link Melati}

    * @param e      the {@link Exception} to report

    */

   public void error(Melati melati, Exception e) {

     ServletTemplateContext templateContext = melati.getServletTemplateContext();

     // If this a DB error which has occurred prior to 

     // the establishment of a template context

     if (templateContext == null) {

       super.error(melati, e);

     } else 

     // has it been trapped already, if so, we don't need to relog it here

     if (!(e instanceof TrappedException)) {

       try {

         // log it

         e.printStackTrace(System.err);

         // and put it on the page

         MelatiWriter mw =  melati.getWriter();

         // get rid of anything that has been written so far

         mw.reset();

         templateContext.put("melati",melati);

         templateContext.put("ml", melati.getMarkupLanguage());

         templateContext.put("object", e);

         StringWriter sw = new StringWriter();

         e.printStackTrace(new PrintWriter(sw));

         templateContext.put("error",sw);

         templateContext.put("sysAdminName", getSysAdminName());

         templateContext.put("sysAdminEmail", getSysAdminEmail());

         Template errorTemplate;

         errorTemplate = melati.getConfig().getTempletLoader().

               templet(melati.getTemplateEngine(), melati.getMarkupLanguage(),"error", e.getClass());

         templateEngine.expandTemplate(mw, errorTemplate, templateContext);

         melati.write();

       } catch (Exception f) {

         System.err.println("Error finding/writing error template:");

         f.printStackTrace();

         super.error(melati,e);

       }

     }

   }

   /**

    * Override this method to build up your own output.

    *

    * @param melati the current Melati

    * @param templateContext the current <code>ServletTemplateContext</code>

    * @return a Template name, possibly excluding extension.

    */

   protected abstract String doTemplateRequest(Melati melati, 

                                               ServletTemplateContext templateContext)

       throws Exception;

 }