// Copyright 2004 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry.vlib;
import java.io.IOException;
import java.rmi.RemoteException;
import javax.ejb.CreateException;
import javax.ejb.FinderException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpSession;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hivemind.ApplicationRuntimeException;
import org.apache.tapestry.IRequestCycle;
import org.apache.tapestry.StaleSessionException;
import org.apache.tapestry.engine.BaseEngine;
import org.apache.tapestry.form.IPropertySelectionModel;
import org.apache.tapestry.request.ResponseOutputStream;
import org.apache.tapestry.vlib.ejb.IBookQuery;
import org.apache.tapestry.vlib.ejb.IBookQueryHome;
import org.apache.tapestry.vlib.ejb.IOperations;
import org.apache.tapestry.vlib.ejb.IOperationsHome;
import org.apache.tapestry.vlib.ejb.Person;
import org.apache.tapestry.vlib.ejb.Publisher;
import org.apache.tapestry.vlib.pages.ApplicationUnavailable;
/**
*
* The engine for the Virtual Library.
* This exists to implement the external
* service, which allows the {@link org.apache.tapestry.vlib.pages.ViewBook}
* and {@link org.apache.tapestry.vlib.pages.ViewPerson}
* pages to be bookmarked, and to provide
* a way for shutting down the application when the user logs out.
*
*
* @version $Id: VirtualLibraryEngine.java,v 1.12 2004/04/30 15:17:22 hlship Exp $
* @author Howard Lewis Ship
*
**/
public class VirtualLibraryEngine extends BaseEngine
{
public static final Log LOG = LogFactory.getLog(VirtualLibraryEngine.class);
private static final boolean DEBUG_ENABLED =
Boolean.getBoolean("org.apache.tapestry.vlib.debug-enabled");
private transient boolean _killSession;
private transient IOperations _operations;
private transient IPropertySelectionModel _publisherModel;
private transient IPropertySelectionModel _personModel;
private transient String _applicationUnavailableMessage;
/**
* Removes the operations bean instance, if accessed this request cycle.
*
* <p>May invalidate the {@link HttpSession} (see {@link #logout()}).
**/
protected void cleanupAfterRequest(IRequestCycle cycle)
{
clearCache();
_applicationUnavailableMessage = null;
if (_killSession)
{
try
{
HttpSession session = cycle.getRequestContext().getSession();
if (session != null)
session.invalidate();
}
catch (IllegalStateException ex)
{
// Ignore.
}
}
}
/**
* Sets the visit property to null, and sets a flag that
* invalidates the {@link HttpSession} at the end of the request cycle.
*
**/
public void logout()
{
Visit visit = (Visit) getVisit();
if (visit != null)
visit.setUser(null);
_killSession = true;
}
public boolean isDebugEnabled()
{
return DEBUG_ENABLED;
}
/**
* Returns an instance of the Vlib Operations beans, which is a stateless
* session bean for performing certain operations.
*
* <p>The bean is automatically removed at the end of the request cycle.
*
**/
public IOperations getOperations()
{
Global global = (Global) getGlobal();
if (_operations == null)
{
int i = 0;
while (true)
{
try
{
IOperationsHome home = global.getOperationsHome();
_operations = home.create();
break;
}
catch (CreateException ex)
{
throw new ApplicationRuntimeException("Error creating operations bean.", ex);
}
catch (RemoteException ex)
{
rmiFailure("Remote exception creating operations bean.", ex, i++);
}
}
}
return _operations;
}
/**
* Builds a model for entering in a publisher name, including an intial
* blank option.
*
**/
public IPropertySelectionModel getPublisherModel()
{
if (_publisherModel == null)
_publisherModel = buildPublisherModel();
return _publisherModel;
}
private IPropertySelectionModel buildPublisherModel()
{
Publisher[] publishers = null;
EntitySelectionModel model = new EntitySelectionModel();
// Add in a default null value, such that the user can
// not select a specific Publisher.
model.add(null, "");
int i = 0;
while (true)
{
IOperations operations = getOperations();
try
{
publishers = operations.getPublishers();
// Exit the retry loop
break;
}
catch (RemoteException ex)
{
rmiFailure("Unable to obtain list of publishers.", ex, i++);
}
}
// Add in the actual publishers. They are sorted by name.
for (i = 0; i < publishers.length; i++)
model.add(publishers[i].getId(), publishers[i].getName());
return model;
}
/**
* Invoked from {@link Visit#clearCache()} (and at the end of the request
* cycle) to clear the publisher and person
* {@link IPropertySelectionModel} models.
*
**/
public void clearCache()
{
_publisherModel = null;
_personModel = null;
Visit visit = (Visit) getVisit();
if (visit != null)
visit.clearCache();
}
/**
* Returns a model that contains all the known Person's, sorted by last name,
* then first. The label for the model matches the user's natural name.
*
**/
public IPropertySelectionModel getPersonModel()
{
if (_personModel == null)
_personModel = buildPersonModel(false);
return _personModel;
}
public IPropertySelectionModel buildPersonModel(boolean includeEmpty)
{
Person[] persons = null;
int i = 0;
while (true)
{
IOperations operations = getOperations();
try
{
persons = operations.getPersons();
break;
}
catch (RemoteException ex)
{
rmiFailure("Unable to obtain list of persons.", ex, i++);
}
}
EntitySelectionModel model = new EntitySelectionModel();
if (includeEmpty)
model.add(null, "");
for (i = 0; i < persons.length; i++)
model.add(persons[i].getId(), persons[i].getNaturalName());
return model;
}
/**
* Creates a new {@link IBookQuery} EJB instance.
*
**/
public IBookQuery createNewQuery()
{
Global global = (Global) getGlobal();
IBookQuery result = null;
int i = 0;
while (true)
{
IBookQueryHome home = global.getBookQueryHome();
try
{
result = home.create();
break;
}
catch (CreateException ex)
{
throw new ApplicationRuntimeException("Could not create BookQuery bean.", ex);
}
catch (RemoteException ex)
{
rmiFailure("Remote exception creating BookQuery bean.", ex, i++);
}
}
return result;
}
/**
* Invoked in various places to present an error message to the user.
* This sets the error property of either the
* {@link org.apache.tapestry.vlib.pages.Home} or
* {@link org.apache.tapestry.vlib.pages.MyLibrary} page
* (the latter only if the user is logged in),
* and sets the selected page for rendering the response.
*
**/
public void presentError(String error, IRequestCycle cycle)
{
String pageName = "Home";
// Get, but don't create, the visit.
Visit visit = (Visit) getVisit();
if (visit != null && visit.isUserLoggedIn())
pageName = "MyLibrary";
IErrorProperty page = (IErrorProperty) cycle.getPage(pageName);
page.setError(error);
cycle.activate(page);
}
/**
* Invoked after an operation on a home or remote interface
* throws a RemoteException; this clears any cache of
* home and remote interfaces.
*
* @param message the message for the exception, or for the log message
* @param ex the exception thrown
* @param attempt the attempt number. Attempt #0 simply clears the EJBs,
* attempt #1 is the real failure.
*
**/
public void rmiFailure(String message, RemoteException ex, int attempt)
{
LOG.error(message, ex);
clearEJBs();
if (attempt > 0)
punt(message, ex);
}
private void punt(String message, Throwable ex)
{
_applicationUnavailableMessage = message;
throw new ApplicationRuntimeException(message, ex);
}
private void clearEJBs()
{
Global global = (Global) getGlobal();
global.clear();
_operations = null;
}
/**
* Invoked when any kind of runtime exception percolates up to the
* top level service method. Normally, the standard Exception
* page is displayed; we logout and setup our own version of the page
* instead.
*
**/
protected void activateExceptionPage(
IRequestCycle cycle,
ResponseOutputStream output,
Throwable cause)
throws ServletException
{
try
{
logout();
ApplicationUnavailable page =
(ApplicationUnavailable) cycle.getPage("ApplicationUnavailable");
String message = _applicationUnavailableMessage;
if (message == null)
message = cause.getMessage();
if (message == null)
message = cause.getClass().getName();
page.activate(message, cause);
cycle.activate(page);
renderResponse(cycle, output);
}
catch (Throwable t)
{
super.activateExceptionPage(cycle, output, cause);
}
}
/**
* Reads a person by id.
*
**/
public Person readPerson(Integer personId)
{
Person result = null;
int i = 0;
while (true)
{
IOperations operations = getOperations();
try
{
result = operations.getPerson(personId);
break;
}
catch (FinderException ex)
{
throw new ApplicationRuntimeException("No such Person #" + personId + ".", ex);
}
catch (RemoteException ex)
{
rmiFailure("Unable to read Person #" + personId + ".", ex, i++);
}
}
return result;
}
protected void handleStaleSessionException(
StaleSessionException ex,
IRequestCycle cycle,
ResponseOutputStream output)
throws IOException, ServletException
{
IMessageProperty home = (IMessageProperty)cycle.getPage("Home");
home.setMessage("You have been logged out due to inactivity.");
redirect("Home", cycle, output, ex);
}
}