src/java/org/apache/turbine/Turbine.java - turbine-core - Git at Google

 package org.apache.turbine;

 /* ====================================================================
  * The Apache Software License, Version 1.1
  *
  * Copyright (c) 2001 The Apache Software Foundation.  All rights
  * reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  *
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
  *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * 3. The end-user documentation included with the redistribution,
  *    if any, must include the following acknowledgment:
  *       "This product includes software developed by the
  *        Apache Software Foundation (http://www.apache.org/)."
  *    Alternately, this acknowledgment may appear in the software itself,
  *    if and wherever such third-party acknowledgments normally appear.
  *
  * 4. The names "Apache" and "Apache Software Foundation" and
  *    "Apache Turbine" must not be used to endorse or promote products
  *    derived from this software without prior written permission. For
  *    written permission, please contact apache@apache.org.
  *
  * 5. Products derived from this software may not be called "Apache",
  *    "Apache Turbine", nor may "Apache" appear in their name, without
  *    prior written permission of the Apache Software Foundation.
  *
  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * ====================================================================
  *
  * This software consists of voluntary contributions made by many
  * individuals on behalf of the Apache Software Foundation.  For more
  * information on the Apache Software Foundation, please see
  * <http://www.apache.org/>.
  */

 // Java Core Classes
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.Enumeration;

 // Java Servlet Classes
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 // Turbine Modules
 import org.apache.turbine.modules.ActionLoader;
 import org.apache.turbine.modules.PageLoader;
 import org.apache.turbine.modules.actions.sessionvalidator.SessionValidator;

 // Turbine Utility Classes
 import org.apache.turbine.util.DynamicURI;
 import org.apache.turbine.util.Log;
 import org.apache.turbine.util.RunData;
 import org.apache.turbine.util.RunDataFactory;
 import org.apache.turbine.util.StringUtils;
 import org.apache.turbine.util.security.AccessControlList;

 //Turbine Services
 import org.apache.turbine.services.TurbineServices;
 import org.apache.turbine.services.resources.TurbineResources;
 import org.apache.turbine.services.logging.LoggingService;
 import org.apache.turbine.services.template.TurbineTemplate;

 /**
  * Turbine is the main servlet for the entire system. It is <code>final</code>
  * because you should <i>not</i> ever need to subclass this servlet.  If you
  * need to perform initialization of a service, then you should implement the
  * Services API and let your code be initialized by it.
  * If you need to override something in the <code>doGet()</code> or
  * <code>doPost()</code> methods, edit the TurbineResources.properties file and
  * specify your own classes there.
  *
  * <p> Turbine servlet recognizes the following initialization parameters.
  *
  * <ul>
  * <li><code>resources</code> the implementation of
  * {@link org.apache.turbine.services.resources.ResourceService} to be used</li>
  * <li><code>properties</code> the path to TurbineResources.properties file
  * used by the default implementation of <code>ResourceService</code>, relative
  * to the application root.</li>
  * <li><code>basedir</code> this parameter is used <strong>only</strong> if your
  * application server does not support web applications, or the or does not
  * support <code>ServletContext.getRealPath(String)</code> method correctly.
  * You can use this parameter to specify the directory within the server's
  * filesystem, that is the base of your web application.</li>
  * </ul><br>
  *
  * @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
  * @author <a href="mailto:bmclaugh@algx.net">Brett McLaughlin</a>
  * @author <a href="mailto:greg@shwoop.com">Greg Ritter</a>
  * @author <a href="mailto:john.mcnally@clearink.com">John D. McNally</a>
  * @author <a href="mailto:frank.kim@clearink.com">Frank Y. Kim</a>
  * @author <a href="mailto:krzewski@e-point.pl">Rafal Krzewski</a>
  * @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
  * @version $Id$
  */
 public class Turbine extends HttpServlet
 {
     /**
      * Name of path info parameter used to indicate the redirected stage of
      * a given user's initial Turbine request
      */
     public static final String REDIRECTED_PATHINFO_NAME = "redirected";

     /**
      * The base directory key
      */
     public static final String BASEDIR_KEY = "basedir";

     /**
      * In certain situations the init() method is called more than once,
      * somtimes even concurrently. This causes bad things to happen,
      * so we use this flag to prevent it.
      */
     private static boolean firstInit = true;

     /**
      * Whether init succeeded or not.
      */
     private static Throwable initFailure = null;

     /**
      * Should initialization activities be performed during doGet()
      * execution?
      */
     private static boolean firstDoGet = true;

     /**
      * This init method will load the default resources from a
      * properties file.
      *
      * @param config typical Servlet initialization parameter.
      * @exception ServletException a servlet exception.
      */
     public final void init(ServletConfig config)
         throws ServletException
     {
         super.init(config);

         synchronized ( this.getClass() )
         {
             if(!firstInit)
             {
                 log ("Double initializaton of Turbine was attempted!");
                 return;
             }
             // executing init will trigger some static initializers, so we have
             // only one chance.
             firstInit = false;

             try
             {
                 // Initalize TurbineServices and init bootstrap services
                 TurbineServices services =
                     (TurbineServices) TurbineServices.getInstance();

                 // Initialize essential services (Resources & Logging)
                 services.initPrimaryServices(config);

                 // Initialize other services that require early init
                 services.initServices(config, false);
             }
             catch ( Exception e )
             {
                 // save the exception to complain loudly later :-)
                 initFailure = e;
                 log ("Turbine: init() failed: " + StringUtils.stackTrace(e));
                 return;
             }
             log ("Turbine: init() Ready to Rumble!");
         }
     }

     /**
      * Initializes the services which need <code>RunData</code> to
      * initialize themselves (post startup).
      *
      * @param data The first <code>GET</code> request.
      */
     public final void init(RunData data)
     {
         if (firstDoGet)
         {
             synchronized (Turbine.class)
             {
                 if (firstDoGet)
                 {
                     log("Turbine: Starting HTTP initialization of services");
                     TurbineServices.getInstance().initServices(data);
                     log("Turbine: Completed HTTP initialization of services");

                     // Mark that we're done.
                     firstDoGet = false;
                }
             }
         }
     }

     /**
      * The <code>Servlet</code> destroy method.  Invokes
      * <code>ServiceBroker</code> tear down method.
      */
     public final void destroy()
     {
         // Shut down all Turbine Services.
         TurbineServices.getInstance().shutdownServices();
         System.gc();

         log("Turbine: Done shutting down!");
     }

     /**
      * The primary method invoked when the Turbine servlet is executed.
      *
      * @param req Servlet request.
      * @param res Servlet response.
      * @exception IOException a servlet exception.
      * @exception ServletException a servlet exception.
      */
     public final void doGet (HttpServletRequest req,
                        HttpServletResponse res)
         throws IOException,
                ServletException
     {
         // Placeholder for the RunData object.
         RunData data = null;
         try
         {
             // Check to make sure that we started up properly.
             if (initFailure != null)
             {
                 throw initFailure;
             }

             // Get general RunData here...
             // Perform turbine specific initialization below.
             data = RunDataFactory.getRunData( req, res,
                                               getServletConfig() );

             // If this is the first invocation, perform some
             // initialization.  Certain services need RunData to initialize
             // themselves.
             init(data);

             // Get the instance of the Session Validator.
             SessionValidator sessionValidator = (SessionValidator)ActionLoader
                 .getInstance().getInstance(TurbineResources.getString(
                     "action.sessionvalidator"));

             // if this is the redirected stage of the initial request,
             // check that the session is now not new.
             // If it is not, then redirect back to the
             // original URL (i.e. remove the "redirected" pathinfo)
             if (data.getParameters()
                 .getString(REDIRECTED_PATHINFO_NAME, "false").equals("true"))
             {
                 if (data.getSession().isNew())
                 {
                     String message = "Infinite redirect detected...";
                     log(message);
                     Log.error(message);
                     throw new Exception(message);
                 }
                 else
                 {
                     DynamicURI duri = new DynamicURI (data, true);

                     // Pass on the sent data in pathinfo.
                     for (Enumeration e = data.getParameters().keys() ;
                          e.hasMoreElements() ;)
                     {
                         String key = (String) e.nextElement();
                         if (!key.equals(REDIRECTED_PATHINFO_NAME))
                         {
                             String value =
                                 (String) data.getParameters().getString ( key );
                             duri.addPathInfo((String)key, (String)value );
                         }
                     }

                     data.getResponse().sendRedirect( duri.toString() );
                     return;
                 }
             }
             else
             {
                 // Insist that the client starts a session before access
                 // to data is allowed. this is done by redirecting them to
                 // the "screen.homepage" page but you could have them go
                 // to any page as a starter (ie: the homepage)
                 // "data.getResponse()" represents the HTTP servlet
                 // response.
                 if ( sessionValidator.requiresNewSession(data) &&
                      data.getSession().isNew() )
                 {
                     DynamicURI duri = new DynamicURI (data, true);

                     // Pass on the sent data in pathinfo.
                     for (Enumeration e = data.getParameters().keys() ;
                          e.hasMoreElements() ;)
                     {
                         String key = (String) e.nextElement();
                         String value =
                             (String) data.getParameters().getString ( key );
                         duri.addPathInfo((String)key, (String)value );
                     }

                     // add a dummy bit of path info to fool browser into
                     // thinking this is a new URL
                     if (!data.getParameters()
                         .containsKey(REDIRECTED_PATHINFO_NAME))
                     {
                         duri.addPathInfo(REDIRECTED_PATHINFO_NAME, "true");
                     }

                     // as the session is new take this opportunity to
                     // set the session timeout if specified in TR.properties
                     int timeout =
                         TurbineResources.getInt("session.timeout", -1);

                     if (timeout != -1)
                     {
                         data.getSession().setMaxInactiveInterval(timeout);
                     }

                     data.getResponse().sendRedirect( duri.toString() );
                     return;
                 }
             }

             // Fill in the screen and action variables.
             data.setScreen ( data.getParameters().getString("screen") );
             data.setAction ( data.getParameters().getString("action") );

             // Special case for login and logout, this must happen before the
             // session validator is executed in order either to allow a user to
             // even login, or to ensure that the session validator gets to
             // mandate its page selection policy for non-logged in users
             // after the logout has taken place.
             if ( data.hasAction()
                     && data.getAction().equalsIgnoreCase(TurbineResources
                             .getString("action.login"))
                     || data.getAction().equalsIgnoreCase(TurbineResources
                             .getString("action.logout")))
             {
                 // If a User is logging in, we should refresh the
                 // session here.  Invalidating session and starting a
                 // new session would seem to be a good method, but I
                 // (JDM) could not get this to work well (it always
                 // required the user to login twice).  Maybe related
                 // to JServ?  If we do not clear out the session, it
                 // is possible a new User may accidently (if they
                 // login incorrectly) continue on with information
                 // associated with the previous User.  Currently the
                 // only keys stored in the session are "turbine.user"
                 // and "turbine.acl".
                 if (data.getAction().equalsIgnoreCase(TurbineResources
                         .getString("action.login")))
                 {
                     String[] names = data.getSession().getValueNames();
                     if (names != null)
                     {
                         for (int i=0; i< names.length; i++)
                         {
                             data.getSession().removeValue(names[i]);
                         }
                     }
                 }
                 ActionLoader.getInstance().exec ( data, data.getAction() );
                 data.setAction(null);
             }

             // This is where the validation of the Session information
             // is performed if the user has not logged in yet, then
             // the screen is set to be Login. This also handles the
             // case of not having a screen defined by also setting the
             // screen to Login. If you want people to go to another
             // screen other than Login, you need to change that within
             // TurbineResources.properties...screen.homepage; or, you
             // can specify your own SessionValidator action.
             ActionLoader.getInstance().exec(
                 data,TurbineResources.getString("action.sessionvalidator") );

             // Put the Access Control List into the RunData object, so
             // it is easily available to modules.  It is also placed
             // into the session for serialization.  Modules can null
             // out the ACL to force it to be rebuilt based on more
             // information.
             ActionLoader.getInstance().exec(
                 data,TurbineResources.getString("action.accesscontroller"));

             // Start the execution phase. DefaultPage will execute the
             // appropriate action as well as get the Layout from the
             // Screen and then execute that. The Layout is then
             // responsible for executing the Navigation and Screen
             // modules.
             //
             // Note that by default, this cannot be overridden from
             // parameters passed in via post/query data. This is for
             // security purposes.  You should really never need more
             // than just the default page.  If you do, add logic to
             // DefaultPage to do what you want.

             String defaultPage = TurbineTemplate.getDefaultPageName(data);

             if (defaultPage == null)
             {
                 /*
                  * In this case none of the template services are running.
                  * The application may be using ECS for views, or a
                  * decendent of RawScreen is trying to produce output.
                  * If there is a 'page.default' property in the TR.props
                  * then use that, otherwise return DefaultPage which will
                  * handle ECS view scenerios and RawScreen scenerios. The
                  * app developer can still specify the 'page.default'
                  * if they wish but the DefaultPage should work in
                  * most cases.
                  */
                 defaultPage = TurbineResources.getString(
                     "page.default", "DefaultPage");
             }

             PageLoader.getInstance().exec(data, defaultPage);

             // If a module has set data.acl = null, remove acl from
             // the session.
             if ( data.getACL() == null )
             {
                 data.getSession().removeValue(
                     AccessControlList.SESSION_KEY);
             }

             try
             {
                 if ( data.isPageSet() == false &&
                      data.isOutSet() == false )
                     throw new Exception ( "Nothing to output" );

                 // We are all done! if isPageSet() output that way
                 // otherwise, data.getOut() has already been written
                 // to the data.getOut().close() happens below in the
                 // finally.
                 if ( data.isPageSet() && data.isOutSet() == false )
                 {
                     // Modules can override these.
                     data.getResponse()
                         .setLocale( data.getLocale() );
                     data.getResponse()
                         .setContentType( data.getContentType() );

                     // Handle the case where a module may want to send
                     // a redirect.
                     if ( ( data.getStatusCode() == 301 ||
                            data.getStatusCode() ==  302 ) &&
                          data.getRedirectURI() != null )
                     {
                         data.getResponse()
                             .sendRedirect ( data.getRedirectURI() );
                     }

                     // Set the status code.
                     data.getResponse().setStatus ( data.getStatusCode() );
                     // Output the Page.
                     data.getPage().output (data.getOut());
                 }
             }
             catch ( Exception e )
             {
                 // The output stream was probably closed by the client
                 // end of things ie: the client clicked the Stop
                 // button on the browser, so ignore any errors that
                 // result.
             }
         }
         catch ( Exception e )
         {
             handleException(data, res, e);
         }
         catch (Throwable t)
         {
             handleException(data, res, t);
         }
         finally
         {
             // Make sure to close the outputstream when we are done.
             try
             {
                 data.getOut().close();
             }
             catch (Exception e)
             {
                 // Ignore.
             }

             // Return the used RunData to the factory for recycling.
             RunDataFactory.putRunData(data);
         }
     }

     /**
      * In this application doGet and doPost are the same thing.
      *
      * @param req Servlet request.
      * @param res Servlet response.
      * @exception IOException a servlet exception.
      * @exception ServletException a servlet exception.
      */
     public final void doPost (HttpServletRequest req,
                         HttpServletResponse res)
         throws IOException,
                ServletException
     {
         doGet ( req, res );
     }

     /**
      * Return the servlet info.
      *
      * @return a string with the servlet information.
      */
     public final String getServletInfo()
     {
         return "Turbine Servlet";
     }

     /**
      * This method is about making sure that we catch and display
      * errors to the screen in one fashion or another. What happens is
      * that it will attempt to show the error using your user defined
      * Error Screen. If that fails, then it will resort to just
      * displaying the error and logging it all over the place
      * including the servlet engine log file, the Turbine log file and
      * on the screen.
      *
      * @param data A Turbine RunData object.
      * @param res Servlet response.
      * @param e The exception to report.
      */
     private final void handleException(RunData data,
                                  HttpServletResponse res,
                                  Throwable t)
     {
         // make sure that the stack trace makes it the log
         Log.error("Turbine.handleException: "+t.getMessage());
         Log.error(t);

         String mimeType = "text/plain";
         try
         {
             // This is where we capture all exceptions and show the
             // Error Screen.
             data.setStackTrace(StringUtils.stackTrace(t),t);

             // setup the screen
             data.setScreen(TurbineResources
                            .getString("screen.error"));

             // do more screen setup for template execution if needed
             if (data.getTemplateInfo() != null)
                 data.getTemplateInfo()
                     .setScreenTemplate(TurbineResources
                                        .getString("template.error"));

             // Make sure to not execute an action.
             data.setAction ("");

             PageLoader.getInstance()
                 .exec(data,
                       TurbineResources.getString("page.default",
                       "DefaultPage"));

             data.getResponse().setContentType( data.getContentType() );
             data.getResponse().setStatus ( data.getStatusCode() );
             if( data.isPageSet() )
                 data.getOut().print ( data.getPage().toString() );
         }
         // Catch this one because it occurs if some code hasn't been
         // completely re-compiled after a change..
         catch ( java.lang.NoSuchFieldError e )
         {
             try
             {
                 data.getResponse().setContentType( mimeType );
                 data.getResponse().setStatus ( 200 );
             }
             catch (Exception ignored) {}

             try
             {
                 data.getOut().print ("java.lang.NoSuchFieldError: " +
                                      "Please recompile all of your " +
                                      "source code.");
             }
             catch (IOException ignored) {}

             log ( data.getStackTrace() );
             org.apache.turbine.util.Log.error ( e.getMessage(), e );
         }
         // Attempt to do *something* at this point...
         catch ( Throwable reallyScrewedNow )
         {
             StringBuffer msg = new StringBuffer();
             msg.append("Horrible Exception: ");
             if (data != null)
             {
                 msg.append(data.getStackTrace());
             }
             else
             {
                 msg.append(t);
             }
             try
             {
                 res.setContentType( mimeType );
                 res.setStatus ( 200 );
                 res.getWriter().print (msg.toString());
             }
             catch (Exception ignored) {}
             org.apache.turbine.util.Log.error (
                     reallyScrewedNow.getMessage(), reallyScrewedNow );
         }
     }
 }
	package org.apache.turbine;

	/* ====================================================================
	* The Apache Software License, Version 1.1
	*
	* Copyright (c) 2001 The Apache Software Foundation. All rights
	* reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	*
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in
	* the documentation and/or other materials provided with the
	* distribution.
	*
	* 3. The end-user documentation included with the redistribution,
	* if any, must include the following acknowledgment:
	* "This product includes software developed by the
	* Apache Software Foundation (http://www.apache.org/)."
	* Alternately, this acknowledgment may appear in the software itself,
	* if and wherever such third-party acknowledgments normally appear.
	*
	* 4. The names "Apache" and "Apache Software Foundation" and
	* "Apache Turbine" must not be used to endorse or promote products
	* derived from this software without prior written permission. For
	* written permission, please contact apache@apache.org.
	*
	* 5. Products derived from this software may not be called "Apache",
	* "Apache Turbine", nor may "Apache" appear in their name, without
	* prior written permission of the Apache Software Foundation.
	*
	* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	* DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
	* ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
	* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
	* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
	* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	* SUCH DAMAGE.
	* ====================================================================
	*
	* This software consists of voluntary contributions made by many
	* individuals on behalf of the Apache Software Foundation. For more
	* information on the Apache Software Foundation, please see
	* <http://www.apache.org/>.
	*/

	// Java Core Classes
	import java.io.IOException;
	import java.io.PrintWriter;
	import java.util.Enumeration;

	// Java Servlet Classes
	import javax.servlet.ServletConfig;
	import javax.servlet.ServletException;
	import javax.servlet.http.HttpServlet;
	import javax.servlet.http.HttpServletRequest;
	import javax.servlet.http.HttpServletResponse;

	// Turbine Modules
	import org.apache.turbine.modules.ActionLoader;
	import org.apache.turbine.modules.PageLoader;
	import org.apache.turbine.modules.actions.sessionvalidator.SessionValidator;

	// Turbine Utility Classes
	import org.apache.turbine.util.DynamicURI;
	import org.apache.turbine.util.Log;
	import org.apache.turbine.util.RunData;
	import org.apache.turbine.util.RunDataFactory;
	import org.apache.turbine.util.StringUtils;
	import org.apache.turbine.util.security.AccessControlList;

	//Turbine Services
	import org.apache.turbine.services.TurbineServices;
	import org.apache.turbine.services.resources.TurbineResources;
	import org.apache.turbine.services.logging.LoggingService;
	import org.apache.turbine.services.template.TurbineTemplate;

	/**
	* Turbine is the main servlet for the entire system. It is <code>final</code>
	* because you should <i>not</i> ever need to subclass this servlet. If you
	* need to perform initialization of a service, then you should implement the
	* Services API and let your code be initialized by it.
	* If you need to override something in the <code>doGet()</code> or
	* <code>doPost()</code> methods, edit the TurbineResources.properties file and
	* specify your own classes there.
	*
	* <p> Turbine servlet recognizes the following initialization parameters.
	*
	* <ul>
	* <li><code>resources</code> the implementation of
	* {@link org.apache.turbine.services.resources.ResourceService} to be used</li>
	* <li><code>properties</code> the path to TurbineResources.properties file
	* used by the default implementation of <code>ResourceService</code>, relative
	* to the application root.</li>
	* <li><code>basedir</code> this parameter is used <strong>only</strong> if your
	* application server does not support web applications, or the or does not
	* support <code>ServletContext.getRealPath(String)</code> method correctly.
	* You can use this parameter to specify the directory within the server's
	* filesystem, that is the base of your web application.</li>
	* </ul><br>
	*
	* @author <a href="mailto:jon@latchkey.com">Jon S. Stevens</a>
	* @author <a href="mailto:bmclaugh@algx.net">Brett McLaughlin</a>
	* @author <a href="mailto:greg@shwoop.com">Greg Ritter</a>
	* @author <a href="mailto:john.mcnally@clearink.com">John D. McNally</a>
	* @author <a href="mailto:frank.kim@clearink.com">Frank Y. Kim</a>
	* @author <a href="mailto:krzewski@e-point.pl">Rafal Krzewski</a>
	* @author <a href="mailto:jvanzyl@apache.org">Jason van Zyl</a>
	* @version $Id$
	*/
	public class Turbine extends HttpServlet
	{
	/**
	* Name of path info parameter used to indicate the redirected stage of
	* a given user's initial Turbine request
	*/
	public static final String REDIRECTED_PATHINFO_NAME = "redirected";

	/**
	* The base directory key
	*/
	public static final String BASEDIR_KEY = "basedir";

	/**
	* In certain situations the init() method is called more than once,
	* somtimes even concurrently. This causes bad things to happen,
	* so we use this flag to prevent it.
	*/
	private static boolean firstInit = true;

	/**
	* Whether init succeeded or not.
	*/
	private static Throwable initFailure = null;

	/**
	* Should initialization activities be performed during doGet()
	* execution?
	*/
	private static boolean firstDoGet = true;

	/**
	* This init method will load the default resources from a
	* properties file.
	*
	* @param config typical Servlet initialization parameter.
	* @exception ServletException a servlet exception.
	*/
	public final void init(ServletConfig config)
	throws ServletException
	{
	super.init(config);

	synchronized ( this.getClass() )
	{
	if(!firstInit)
	{
	log ("Double initializaton of Turbine was attempted!");
	return;
	}
	// executing init will trigger some static initializers, so we have
	// only one chance.
	firstInit = false;

	try
	{
	// Initalize TurbineServices and init bootstrap services
	TurbineServices services =
	(TurbineServices) TurbineServices.getInstance();

	// Initialize essential services (Resources & Logging)
	services.initPrimaryServices(config);

	// Initialize other services that require early init
	services.initServices(config, false);
	}
	catch ( Exception e )
	{
	// save the exception to complain loudly later :-)
	initFailure = e;
	log ("Turbine: init() failed: " + StringUtils.stackTrace(e));
	return;
	}
	log ("Turbine: init() Ready to Rumble!");
	}
	}

	/**
	* Initializes the services which need <code>RunData</code> to
	* initialize themselves (post startup).
	*
	* @param data The first <code>GET</code> request.
	*/
	public final void init(RunData data)
	{
	if (firstDoGet)
	{
	synchronized (Turbine.class)
	{
	if (firstDoGet)
	{
	log("Turbine: Starting HTTP initialization of services");
	TurbineServices.getInstance().initServices(data);
	log("Turbine: Completed HTTP initialization of services");

	// Mark that we're done.
	firstDoGet = false;
	}
	}
	}
	}

	/**
	* The <code>Servlet</code> destroy method. Invokes
	* <code>ServiceBroker</code> tear down method.
	*/
	public final void destroy()
	{
	// Shut down all Turbine Services.
	TurbineServices.getInstance().shutdownServices();
	System.gc();

	log("Turbine: Done shutting down!");
	}

	/**
	* The primary method invoked when the Turbine servlet is executed.
	*
	* @param req Servlet request.
	* @param res Servlet response.
	* @exception IOException a servlet exception.
	* @exception ServletException a servlet exception.
	*/
	public final void doGet (HttpServletRequest req,
	HttpServletResponse res)
	throws IOException,
	ServletException
	{
	// Placeholder for the RunData object.
	RunData data = null;
	try
	{
	// Check to make sure that we started up properly.
	if (initFailure != null)
	{
	throw initFailure;
	}

	// Get general RunData here...
	// Perform turbine specific initialization below.
	data = RunDataFactory.getRunData( req, res,
	getServletConfig() );

	// If this is the first invocation, perform some
	// initialization. Certain services need RunData to initialize
	// themselves.
	init(data);

	// Get the instance of the Session Validator.
	SessionValidator sessionValidator = (SessionValidator)ActionLoader
	.getInstance().getInstance(TurbineResources.getString(
	"action.sessionvalidator"));

	// if this is the redirected stage of the initial request,
	// check that the session is now not new.
	// If it is not, then redirect back to the
	// original URL (i.e. remove the "redirected" pathinfo)
	if (data.getParameters()
	.getString(REDIRECTED_PATHINFO_NAME, "false").equals("true"))
	{
	if (data.getSession().isNew())
	{
	String message = "Infinite redirect detected...";
	log(message);
	Log.error(message);
	throw new Exception(message);
	}
	else
	{
	DynamicURI duri = new DynamicURI (data, true);

	// Pass on the sent data in pathinfo.
	for (Enumeration e = data.getParameters().keys() ;
	e.hasMoreElements() ;)
	{
	String key = (String) e.nextElement();
	if (!key.equals(REDIRECTED_PATHINFO_NAME))
	{
	String value =
	(String) data.getParameters().getString ( key );
	duri.addPathInfo((String)key, (String)value );
	}
	}

	data.getResponse().sendRedirect( duri.toString() );
	return;
	}
	}
	else
	{
	// Insist that the client starts a session before access
	// to data is allowed. this is done by redirecting them to
	// the "screen.homepage" page but you could have them go
	// to any page as a starter (ie: the homepage)
	// "data.getResponse()" represents the HTTP servlet
	// response.
	if ( sessionValidator.requiresNewSession(data) &&
	data.getSession().isNew() )
	{
	DynamicURI duri = new DynamicURI (data, true);

	// Pass on the sent data in pathinfo.
	for (Enumeration e = data.getParameters().keys() ;
	e.hasMoreElements() ;)
	{
	String key = (String) e.nextElement();
	String value =
	(String) data.getParameters().getString ( key );
	duri.addPathInfo((String)key, (String)value );
	}

	// add a dummy bit of path info to fool browser into
	// thinking this is a new URL
	if (!data.getParameters()
	.containsKey(REDIRECTED_PATHINFO_NAME))
	{
	duri.addPathInfo(REDIRECTED_PATHINFO_NAME, "true");
	}

	// as the session is new take this opportunity to
	// set the session timeout if specified in TR.properties
	int timeout =
	TurbineResources.getInt("session.timeout", -1);

	if (timeout != -1)
	{
	data.getSession().setMaxInactiveInterval(timeout);
	}

	data.getResponse().sendRedirect( duri.toString() );
	return;
	}
	}

	// Fill in the screen and action variables.
	data.setScreen ( data.getParameters().getString("screen") );
	data.setAction ( data.getParameters().getString("action") );

	// Special case for login and logout, this must happen before the
	// session validator is executed in order either to allow a user to
	// even login, or to ensure that the session validator gets to
	// mandate its page selection policy for non-logged in users
	// after the logout has taken place.
	if ( data.hasAction()
	&& data.getAction().equalsIgnoreCase(TurbineResources
	.getString("action.login"))
	\|\| data.getAction().equalsIgnoreCase(TurbineResources
	.getString("action.logout")))
	{
	// If a User is logging in, we should refresh the
	// session here. Invalidating session and starting a
	// new session would seem to be a good method, but I
	// (JDM) could not get this to work well (it always
	// required the user to login twice). Maybe related
	// to JServ? If we do not clear out the session, it
	// is possible a new User may accidently (if they
	// login incorrectly) continue on with information
	// associated with the previous User. Currently the
	// only keys stored in the session are "turbine.user"
	// and "turbine.acl".
	if (data.getAction().equalsIgnoreCase(TurbineResources
	.getString("action.login")))
	{
	String[] names = data.getSession().getValueNames();
	if (names != null)
	{
	for (int i=0; i< names.length; i++)
	{
	data.getSession().removeValue(names[i]);
	}
	}
	}
	ActionLoader.getInstance().exec ( data, data.getAction() );
	data.setAction(null);
	}

	// This is where the validation of the Session information
	// is performed if the user has not logged in yet, then
	// the screen is set to be Login. This also handles the
	// case of not having a screen defined by also setting the
	// screen to Login. If you want people to go to another
	// screen other than Login, you need to change that within
	// TurbineResources.properties...screen.homepage; or, you
	// can specify your own SessionValidator action.
	ActionLoader.getInstance().exec(
	data,TurbineResources.getString("action.sessionvalidator") );

	// Put the Access Control List into the RunData object, so
	// it is easily available to modules. It is also placed
	// into the session for serialization. Modules can null
	// out the ACL to force it to be rebuilt based on more
	// information.
	ActionLoader.getInstance().exec(
	data,TurbineResources.getString("action.accesscontroller"));

	// Start the execution phase. DefaultPage will execute the
	// appropriate action as well as get the Layout from the
	// Screen and then execute that. The Layout is then
	// responsible for executing the Navigation and Screen
	// modules.
	//
	// Note that by default, this cannot be overridden from
	// parameters passed in via post/query data. This is for
	// security purposes. You should really never need more
	// than just the default page. If you do, add logic to
	// DefaultPage to do what you want.

	String defaultPage = TurbineTemplate.getDefaultPageName(data);

	if (defaultPage == null)
	{
	/*
	* In this case none of the template services are running.
	* The application may be using ECS for views, or a
	* decendent of RawScreen is trying to produce output.
	* If there is a 'page.default' property in the TR.props
	* then use that, otherwise return DefaultPage which will
	* handle ECS view scenerios and RawScreen scenerios. The
	* app developer can still specify the 'page.default'
	* if they wish but the DefaultPage should work in
	* most cases.
	*/
	defaultPage = TurbineResources.getString(
	"page.default", "DefaultPage");
	}

	PageLoader.getInstance().exec(data, defaultPage);

	// If a module has set data.acl = null, remove acl from
	// the session.
	if ( data.getACL() == null )
	{
	data.getSession().removeValue(
	AccessControlList.SESSION_KEY);
	}

	try
	{
	if ( data.isPageSet() == false &&
	data.isOutSet() == false )
	throw new Exception ( "Nothing to output" );

	// We are all done! if isPageSet() output that way
	// otherwise, data.getOut() has already been written
	// to the data.getOut().close() happens below in the
	// finally.
	if ( data.isPageSet() && data.isOutSet() == false )
	{
	// Modules can override these.
	data.getResponse()
	.setLocale( data.getLocale() );
	data.getResponse()
	.setContentType( data.getContentType() );

	// Handle the case where a module may want to send
	// a redirect.
	if ( ( data.getStatusCode() == 301 \|\|
	data.getStatusCode() == 302 ) &&
	data.getRedirectURI() != null )
	{
	data.getResponse()
	.sendRedirect ( data.getRedirectURI() );
	}

	// Set the status code.
	data.getResponse().setStatus ( data.getStatusCode() );
	// Output the Page.
	data.getPage().output (data.getOut());
	}
	}
	catch ( Exception e )
	{
	// The output stream was probably closed by the client
	// end of things ie: the client clicked the Stop
	// button on the browser, so ignore any errors that
	// result.
	}
	}
	catch ( Exception e )
	{
	handleException(data, res, e);
	}
	catch (Throwable t)
	{
	handleException(data, res, t);
	}
	finally
	{
	// Make sure to close the outputstream when we are done.
	try
	{
	data.getOut().close();
	}
	catch (Exception e)
	{
	// Ignore.
	}

	// Return the used RunData to the factory for recycling.
	RunDataFactory.putRunData(data);
	}
	}

	/**
	* In this application doGet and doPost are the same thing.
	*
	* @param req Servlet request.
	* @param res Servlet response.
	* @exception IOException a servlet exception.
	* @exception ServletException a servlet exception.
	*/
	public final void doPost (HttpServletRequest req,
	HttpServletResponse res)
	throws IOException,
	ServletException
	{
	doGet ( req, res );
	}

	/**
	* Return the servlet info.
	*
	* @return a string with the servlet information.
	*/
	public final String getServletInfo()
	{
	return "Turbine Servlet";
	}

	/**
	* This method is about making sure that we catch and display
	* errors to the screen in one fashion or another. What happens is
	* that it will attempt to show the error using your user defined
	* Error Screen. If that fails, then it will resort to just
	* displaying the error and logging it all over the place
	* including the servlet engine log file, the Turbine log file and
	* on the screen.
	*
	* @param data A Turbine RunData object.
	* @param res Servlet response.
	* @param e The exception to report.
	*/
	private final void handleException(RunData data,
	HttpServletResponse res,
	Throwable t)
	{
	// make sure that the stack trace makes it the log
	Log.error("Turbine.handleException: "+t.getMessage());
	Log.error(t);

	String mimeType = "text/plain";
	try
	{
	// This is where we capture all exceptions and show the
	// Error Screen.
	data.setStackTrace(StringUtils.stackTrace(t),t);

	// setup the screen
	data.setScreen(TurbineResources
	.getString("screen.error"));

	// do more screen setup for template execution if needed
	if (data.getTemplateInfo() != null)
	data.getTemplateInfo()
	.setScreenTemplate(TurbineResources
	.getString("template.error"));

	// Make sure to not execute an action.
	data.setAction ("");

	PageLoader.getInstance()
	.exec(data,
	TurbineResources.getString("page.default",
	"DefaultPage"));

	data.getResponse().setContentType( data.getContentType() );
	data.getResponse().setStatus ( data.getStatusCode() );
	if( data.isPageSet() )
	data.getOut().print ( data.getPage().toString() );
	}
	// Catch this one because it occurs if some code hasn't been
	// completely re-compiled after a change..
	catch ( java.lang.NoSuchFieldError e )
	{
	try
	{
	data.getResponse().setContentType( mimeType );
	data.getResponse().setStatus ( 200 );
	}
	catch (Exception ignored) {}

	try
	{
	data.getOut().print ("java.lang.NoSuchFieldError: " +
	"Please recompile all of your " +
	"source code.");
	}
	catch (IOException ignored) {}

	log ( data.getStackTrace() );
	org.apache.turbine.util.Log.error ( e.getMessage(), e );
	}
	// Attempt to do something at this point...
	catch ( Throwable reallyScrewedNow )
	{
	StringBuffer msg = new StringBuffer();
	msg.append("Horrible Exception: ");
	if (data != null)
	{
	msg.append(data.getStackTrace());
	}
	else
	{
	msg.append(t);
	}
	try
	{
	res.setContentType( mimeType );
	res.setStatus ( 200 );
	res.getWriter().print (msg.toString());
	}
	catch (Exception ignored) {}
	org.apache.turbine.util.Log.error (
	reallyScrewedNow.getMessage(), reallyScrewedNow );
	}
	}
	}