001 // Copyright 2004, 2005 The Apache Software Foundation
002 //
003 // Licensed under the Apache License, Version 2.0 (the "License");
004 // you may not use this file except in compliance with the License.
005 // You may obtain a copy of the License at
006 //
007 // http://www.apache.org/licenses/LICENSE-2.0
008 //
009 // Unless required by applicable law or agreed to in writing, software
010 // distributed under the License is distributed on an "AS IS" BASIS,
011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012 // See the License for the specific language governing permissions and
013 // limitations under the License.
014
015 package org.apache.tapestry.engine;
016
017 import java.io.IOException;
018 import java.util.ArrayList;
019 import java.util.List;
020 import java.util.Locale;
021
022 import org.apache.commons.logging.Log;
023 import org.apache.commons.logging.LogFactory;
024 import org.apache.hivemind.ApplicationRuntimeException;
025 import org.apache.hivemind.ClassResolver;
026 import org.apache.hivemind.util.Defense;
027 import org.apache.hivemind.util.ToStringBuilder;
028 import org.apache.tapestry.Constants;
029 import org.apache.tapestry.IEngine;
030 import org.apache.tapestry.IPage;
031 import org.apache.tapestry.IRequestCycle;
032 import org.apache.tapestry.PageRedirectException;
033 import org.apache.tapestry.RedirectException;
034 import org.apache.tapestry.StaleLinkException;
035 import org.apache.tapestry.StaleSessionException;
036 import org.apache.tapestry.listener.ListenerMap;
037 import org.apache.tapestry.services.DataSqueezer;
038 import org.apache.tapestry.services.Infrastructure;
039 import org.apache.tapestry.spec.IApplicationSpecification;
040 import org.apache.tapestry.web.WebRequest;
041 import org.apache.tapestry.web.WebResponse;
042
043 /**
044 * Basis for building real Tapestry applications. Immediate subclasses provide different strategies
045 * for managing page state and other resources between request cycles.
046 * <p>
047 * Note: much of this description is <em>in transition</em> as part of Tapestry 4.0. All ad-hoc
048 * singletons and such are being replaced with HiveMind services.
049 * <p>
050 * Uses a shared instance of {@link ITemplateSource},{@link ISpecificationSource},
051 * {@link IScriptSource}and {@link IComponentMessagesSource}stored as attributes of the
052 * {@link ServletContext}(they will be shared by all sessions).
053 * <p>
054 * An engine is designed to be very lightweight. Particularily, it should <b>never </b> hold
055 * references to any {@link IPage}or {@link org.apache.tapestry.IComponent}objects. The entire
056 * system is based upon being able to quickly rebuild the state of any page(s).
057 * <p>
058 * Where possible, instance variables should be transient. They can be restored inside
059 * {@link #setupForRequest(RequestContext)}.
060 * <p>
061 * In practice, a subclass (usually {@link BaseEngine}) is used without subclassing. Instead, a
062 * visit object is specified. To facilitate this, the application specification may include a
063 * property, <code>org.apache.tapestry.visit-class</code> which is the class name to instantiate
064 * when a visit object is first needed. See {@link #createVisit(IRequestCycle)}for more details.
065 * <p>
066 * Some of the classes' behavior is controlled by JVM system properties (typically only used during
067 * development): <table border=1>
068 * <tr>
069 * <th>Property</th>
070 * <th>Description</th>
071 * </tr>
072 * <tr>
073 * <td>org.apache.tapestry.enable-reset-service</td>
074 * <td>If true, enabled an additional service, reset, that allow page, specification and template
075 * caches to be cleared on demand. See {@link #isResetServiceEnabled()}.</td>
076 * </tr>
077 * <tr>
078 * <td>org.apache.tapestry.disable-caching</td>
079 * <td>If true, then the page, specification, template and script caches will be cleared after each
080 * request. This slows things down, but ensures that the latest versions of such files are used.
081 * Care should be taken that the source directories for the files preceeds any versions of the files
082 * available in JARs or WARs.</td>
083 * </tr>
084 * </table>
085 *
086 * @author Howard Lewis Ship
087 */
088
089 public abstract class AbstractEngine implements IEngine
090 {
091 /**
092 * The name of the application specification property used to specify the class of the visit
093 * object.
094 */
095
096 public static final String VISIT_CLASS_PROPERTY_NAME = "org.apache.tapestry.visit-class";
097
098 private static final Log LOG = LogFactory.getLog(AbstractEngine.class);
099
100 /**
101 * The link to the world of HiveMind services.
102 *
103 * @since 4.0
104 */
105 private Infrastructure _infrastructure;
106
107 private ListenerMap _listeners;
108
109 /**
110 * The curent locale for the engine, which may be changed at any time.
111 */
112
113 private Locale _locale;
114
115 /**
116 * @see org.apache.tapestry.error.ExceptionPresenter
117 */
118
119 protected void activateExceptionPage(IRequestCycle cycle, Throwable cause)
120 {
121 _infrastructure.getExceptionPresenter().presentException(cycle, cause);
122 }
123
124 /**
125 * Writes a detailed report of the exception to <code>System.err</code>.
126 *
127 * @see org.apache.tapestry.error.RequestExceptionReporter
128 */
129
130 public void reportException(String reportTitle, Throwable ex)
131 {
132 _infrastructure.getRequestExceptionReporter().reportRequestException(reportTitle, ex);
133 }
134
135 /**
136 * Invoked at the end of the request cycle to release any resources specific to the request
137 * cycle. This implementation does nothing and may be overriden freely.
138 */
139
140 protected void cleanupAfterRequest(IRequestCycle cycle)
141 {
142
143 }
144
145 /**
146 * Returns the locale for the engine. This is initially set by the {@link ApplicationServlet}
147 * but may be updated by the application.
148 */
149
150 public Locale getLocale()
151 {
152 return _locale;
153 }
154
155 /**
156 * Returns a service with the given name.
157 *
158 * @see Infrastructure#getServiceMap()
159 * @see org.apache.tapestry.services.ServiceMap
160 */
161
162 public IEngineService getService(String name)
163 {
164 return _infrastructure.getServiceMap().getService(name);
165 }
166
167 /** @see Infrastructure#getApplicationSpecification() */
168
169 public IApplicationSpecification getSpecification()
170 {
171 return _infrastructure.getApplicationSpecification();
172 }
173
174 /** @see Infrastructure#getSpecificationSource() */
175
176 public ISpecificationSource getSpecificationSource()
177 {
178 return _infrastructure.getSpecificationSource();
179 }
180
181 /**
182 * Invoked, typically, when an exception occurs while servicing the request. This method resets
183 * the output, sets the new page and renders it.
184 */
185
186 protected void redirect(String pageName, IRequestCycle cycle,
187 ApplicationRuntimeException exception) throws IOException
188 {
189 IPage page = cycle.getPage(pageName);
190
191 cycle.activate(page);
192
193 renderResponse(cycle);
194 }
195
196 /**
197 * Delegates to
198 * {@link org.apache.tapestry.services.ResponseRenderer#renderResponse(IRequestCycle)}.
199 */
200
201 public void renderResponse(IRequestCycle cycle) throws IOException
202 {
203 _infrastructure.getResponseRenderer().renderResponse(cycle);
204 }
205
206 /**
207 * Delegate method for the servlet. Services the request.
208 */
209
210 public void service(WebRequest request, WebResponse response) throws IOException
211 {
212 IRequestCycle cycle = null;
213 IEngineService service = null;
214
215 if (_infrastructure == null)
216 _infrastructure = (Infrastructure) request.getAttribute(Constants.INFRASTRUCTURE_KEY);
217
218 // Create the request cycle; if this fails, there's not much that can be done ... everything
219 // else in Tapestry relies on the RequestCycle.
220
221 try
222 {
223 cycle = _infrastructure.getRequestCycleFactory().newRequestCycle(this);
224 }
225 catch (RuntimeException ex)
226 {
227 throw ex;
228 }
229 catch (Exception ex)
230 {
231 throw new IOException(ex.getMessage());
232 }
233
234 try
235 {
236 try
237 {
238 service = cycle.getService();
239 // Let the service handle the rest of the request.
240
241 service.service(cycle);
242
243 return;
244 }
245 catch (PageRedirectException ex)
246 {
247 handlePageRedirectException(cycle, ex);
248 }
249 catch (RedirectException ex)
250 {
251 handleRedirectException(cycle, ex);
252 }
253 catch (StaleLinkException ex)
254 {
255 handleStaleLinkException(cycle, ex);
256 }
257 catch (StaleSessionException ex)
258 {
259 handleStaleSessionException(cycle, ex);
260 }
261 }
262 catch (Exception ex)
263 {
264 // Attempt to switch to the exception page. However, this may itself
265 // fail for a number of reasons, in which case an ApplicationRuntimeException is
266 // thrown.
267
268 if (LOG.isDebugEnabled())
269 LOG.debug("Uncaught exception", ex);
270
271 activateExceptionPage(cycle, ex);
272 }
273 finally
274 {
275 try
276 {
277 cycle.cleanup();
278 _infrastructure.getApplicationStateManager().flush();
279 }
280 catch (Exception ex)
281 {
282 reportException(EngineMessages.exceptionDuringCleanup(ex), ex);
283 }
284 }
285 }
286
287 /**
288 * Handles {@link PageRedirectException} which involves executing
289 * {@link IRequestCycle#activate(IPage)} on the target page (of the exception), until either a
290 * loop is found, or a page succesfully activates.
291 * <p>
292 * This should generally not be overriden in subclasses.
293 *
294 * @since 3.0
295 */
296
297 protected void handlePageRedirectException(IRequestCycle cycle, PageRedirectException exception)
298 throws IOException
299 {
300 List pageNames = new ArrayList();
301
302 String pageName = exception.getTargetPageName();
303
304 while (true)
305 {
306 if (pageNames.contains(pageName))
307 {
308 pageNames.add(pageName);
309
310 throw new ApplicationRuntimeException(EngineMessages.validateCycle(pageNames));
311 }
312
313 // Record that this page has been a target.
314
315 pageNames.add(pageName);
316
317 try
318 {
319 // Attempt to activate the new page.
320
321 cycle.activate(pageName);
322
323 break;
324 }
325 catch (PageRedirectException secondRedirectException)
326 {
327 pageName = secondRedirectException.getTargetPageName();
328 }
329 }
330
331 renderResponse(cycle);
332 }
333
334 /**
335 * Invoked by {@link #service(WebRequest, WebResponse)} if a {@link StaleLinkException} is
336 * thrown by the {@link IEngineService service}. This implementation sets the message property
337 * of the StaleLink page to the message provided in the exception, then invokes
338 * {@link #redirect(String, IRequestCycle, ApplicationRuntimeException)} to render the StaleLink
339 * page.
340 * <p>
341 * Subclasses may overide this method (without invoking this implementation). A better practice
342 * is to contribute an alternative implementation of
343 * {@link org.apache.tapestry.error.StaleLinkExceptionPresenter} to the
344 * tapestry.InfrastructureOverrides configuration point.
345 * <p>
346 * A common practice is to present an error message on the application's Home page. Alternately,
347 * the application may provide its own version of the StaleLink page, overriding the framework's
348 * implementation (probably a good idea, because the default page hints at "application errors"
349 * and isn't localized). The overriding StaleLink implementation must implement a message
350 * property of type String.
351 *
352 * @since 0.2.10
353 */
354
355 protected void handleStaleLinkException(IRequestCycle cycle, StaleLinkException exception)
356 throws IOException
357 {
358 _infrastructure.getStaleLinkExceptionPresenter()
359 .presentStaleLinkException(cycle, exception);
360 }
361
362 /**
363 * Invoked by {@link #service(WebRequest, WebResponse)} if a {@link StaleSessionException} is
364 * thrown by the {@link IEngineService service}. This implementation uses the
365 * {@link org.apache.tapestry.error.StaleSessionExceptionPresenter} to render the StaleSession
366 * page.
367 * <p>
368 * Subclasses may overide this method (without invoking this implementation), but it is better
369 * to override the tapestry.error.StaleSessionExceptionReporter service instead (or contribute a
370 * replacement to the tapestry.InfrastructureOverrides configuration point).
371 *
372 * @since 0.2.10
373 */
374
375 protected void handleStaleSessionException(IRequestCycle cycle, StaleSessionException exception)
376 throws IOException
377 {
378 _infrastructure.getStaleSessionExceptionPresenter().presentStaleSessionException(
379 cycle,
380 exception);
381 }
382
383 /**
384 * Changes the locale for the engine.
385 */
386
387 public void setLocale(Locale value)
388 {
389 Defense.notNull(value, "locale");
390
391 _locale = value;
392
393 // The locale may be set before the engine is initialized with the Infrastructure.
394
395 if (_infrastructure != null)
396 _infrastructure.setLocale(value);
397 }
398
399 /**
400 * @see Infrastructure#getClassResolver()
401 */
402
403 public ClassResolver getClassResolver()
404 {
405 return _infrastructure.getClassResolver();
406 }
407
408 /**
409 * Generates a description of the instance. Invokes {@link #extendDescription(ToStringBuilder)}
410 * to fill in details about the instance.
411 *
412 * @see #extendDescription(ToStringBuilder)
413 */
414
415 public String toString()
416 {
417 ToStringBuilder builder = new ToStringBuilder(this);
418
419 builder.append("locale", _locale);
420
421 return builder.toString();
422 }
423
424 /**
425 * Gets the visit object from the
426 * {@link org.apache.tapestry.engine.state.ApplicationStateManager}, creating it if it does not
427 * already exist.
428 * <p>
429 * As of Tapestry 4.0, this will always create the visit object, possibly creating a new session
430 * in the process.
431 */
432
433 public Object getVisit()
434 {
435 return _infrastructure.getApplicationStateManager().get("visit");
436 }
437
438 public void setVisit(Object visit)
439 {
440 _infrastructure.getApplicationStateManager().store("visit", visit);
441 }
442
443 /**
444 * Gets the visit object from the
445 * {@link org.apache.tapestry.engine.state.ApplicationStateManager}, which will create it as
446 * necessary.
447 */
448
449 public Object getVisit(IRequestCycle cycle)
450 {
451 return getVisit();
452 }
453
454 public boolean getHasVisit()
455 {
456 return _infrastructure.getApplicationStateManager().exists("visit");
457 }
458
459 /**
460 * Returns the global object for the application. The global object is created at the start of
461 * the request ({@link #setupForRequest(RequestContext)}invokes
462 * {@link #createGlobal(RequestContext)}if needed), and is stored into the
463 * {@link ServletContext}. All instances of the engine for the application share the global
464 * object; however, the global object is explicitly <em>not</em> replicated to other servers
465 * within a cluster.
466 *
467 * @since 2.3
468 */
469
470 public Object getGlobal()
471 {
472 return _infrastructure.getApplicationStateManager().get("global");
473 }
474
475 public IScriptSource getScriptSource()
476 {
477 return _infrastructure.getScriptSource();
478 }
479
480 /**
481 * Allows subclasses to include listener methods easily.
482 *
483 * @since 1.0.2
484 */
485
486 public ListenerMap getListeners()
487 {
488 if (_listeners == null)
489 _listeners = _infrastructure.getListenerMapSource().getListenerMapForObject(this);
490
491 return _listeners;
492 }
493
494 /**
495 * Invoked when a {@link RedirectException} is thrown during the processing of a request.
496 *
497 * @throws ApplicationRuntimeException
498 * if an {@link IOException},{@link ServletException}is thrown by the redirect,
499 * or if no {@link RequestDispatcher}can be found for local resource.
500 * @since 2.2
501 */
502
503 protected void handleRedirectException(IRequestCycle cycle, RedirectException redirectException)
504 {
505 String location = redirectException.getRedirectLocation();
506
507 if (LOG.isDebugEnabled())
508 LOG.debug("Redirecting to: " + location);
509
510 _infrastructure.getRequest().forward(location);
511 }
512
513 /**
514 * @see Infrastructure#getDataSqueezer()
515 */
516
517 public DataSqueezer getDataSqueezer()
518 {
519 return _infrastructure.getDataSqueezer();
520 }
521
522 /** @since 2.3 */
523
524 public IPropertySource getPropertySource()
525 {
526 return _infrastructure.getApplicationPropertySource();
527 }
528
529 /** @since 4.0 */
530 public Infrastructure getInfrastructure()
531 {
532 return _infrastructure;
533 }
534
535 public String getOutputEncoding()
536 {
537 return _infrastructure.getOutputEncoding();
538 }
539 }