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;
016
017 import org.apache.tapestry.engine.IEngineService;
018 import org.apache.tapestry.engine.IMonitor;
019 import org.apache.tapestry.request.RequestContext;
020 import org.apache.tapestry.services.Infrastructure;
021
022 /**
023 * Controller object that manages a single request cycle. A request cycle is one 'hit' on the web
024 * server. In the case of a Tapestry application, this will involve:
025 * <ul>
026 * <li>Responding to the URL by finding an {@link IEngineService}object
027 * <li>Determining the result page
028 * <li>Renderring the result page
029 * <li>Releasing any resources
030 * </ul>
031 * <p>
032 * Mixed in with this is:
033 * <ul>
034 * <li>Exception handling
035 * <li>Loading of pages and templates from resources
036 * <li>Tracking changes to page properties, and restoring pages to prior states
037 * <li>Pooling of page objects
038 * </ul>
039 * <p>
040 * A request cycle is broken up into two phases. The <em>rewind</em> phase is optional, as it tied
041 * to {@link org.apache.tapestry.link.ActionLink}or {@link org.apache.tapestry.form.Form}
042 * components. In the rewind phase, a previous page render is redone (discarding output) until a
043 * specific component of the page is reached. This rewinding ensures that the page is restored to
044 * the exact state it had when the URL for the request cycle was generated, taking into account the
045 * dynamic nature of the page ({@link org.apache.tapestry.components.Foreach},
046 * {@link org.apache.tapestry.components.Conditional}, etc.). Once this component is reached, it
047 * can notify its {@link IActionListener}. The listener has the ability to update the state of any
048 * pages and select a new result page.
049 * <p>
050 * Following the rewind phase is the <em>render</em> phase. During the render phase, a page is
051 * actually rendered and output sent to the client web browser.
052 *
053 * @author Howard Lewis Ship
054 */
055
056 public interface IRequestCycle
057 {
058 /**
059 * Invoked after the request cycle is no longer needed, to release any resources it may have.
060 * This includes releasing any loaded pages back to the page source.
061 */
062
063 public void cleanup();
064
065 /**
066 * Passes the String through
067 * {@link javax.servlet.http.HttpServletResponse#encodeURL(java.lang.String)}, which ensures
068 * that the session id is encoded in the URL (if necessary).
069 */
070
071 public String encodeURL(String URL);
072
073 /**
074 * Returns the engine which is processing this request cycle.
075 */
076
077 public IEngine getEngine();
078
079 /**
080 * Retrieves a previously stored attribute, returning null if not found. Attributes allow
081 * components to locate each other; primarily they allow a wrapped component to locate a
082 * component which wraps it. Attributes are cleared at the end of the render (or rewind).
083 */
084
085 public Object getAttribute(String name);
086
087 public IMonitor getMonitor();
088
089 /**
090 * Returns the next action id. ActionLink ids are used to identify different actions on a page
091 * (URLs that are related to dynamic page state).
092 *
093 * @deprecated To be removed in release 4.1 with no replacement.
094 * @see #getUniqueId(String)
095 */
096
097 public String getNextActionId();
098
099 /**
100 * Identifies the active page, the page which will ultimately render the response.
101 */
102
103 public IPage getPage();
104
105 /**
106 * Returns the page with the given name. If the page has been previously loaded in the current
107 * request cycle, that page is returned. Otherwise, the engine's page loader is used to load the
108 * page.
109 *
110 * @throws PageNotFoundException
111 * if the page does not exist.
112 * @see org.apache.tapestry.engine.IPageSource#getPage(IRequestCycle, String, IMonitor)
113 */
114
115 public IPage getPage(String name);
116
117 /**
118 * Returns true if the context is being used to rewind a prior state of the page. This is only
119 * true when there is a target action id.
120 */
121
122 public boolean isRewinding();
123
124 /**
125 * Checks to see if the current action id matches the target action id. Returns true only if
126 * they match. Returns false if there is no target action id (that is, during page rendering).
127 * <p>
128 * If theres a match on action id, then the component is compared against the target component.
129 * If there's a mismatch then a {@link StaleLinkException}is thrown.
130 */
131
132 public boolean isRewound(IComponent component) throws StaleLinkException;
133
134 /**
135 * Removes a previously stored attribute, if one with the given name exists.
136 */
137
138 public void removeAttribute(String name);
139
140 /**
141 * Renders the given page. Applications should always use this method to render the page, rather
142 * than directly invoking {@link IPage#render(IMarkupWriter, IRequestCycle)}since the request
143 * cycle must perform some setup before rendering.
144 */
145
146 public void renderPage(IMarkupWriter writer);
147
148 /**
149 * Rewinds a page and executes some form of action when the component with the specified action
150 * id is reached.
151 *
152 * @see IAction
153 * @see org.apache.tapestry.link.ActionLink
154 * @deprecated To be removed in 4.1 with no replacement.
155 */
156
157 public void rewindPage(String targetActionId, IComponent targetComponent);
158
159 /**
160 * Allows a temporary object to be stored in the request cycle, which allows otherwise unrelated
161 * objects to communicate. This is similar to <code>HttpServletRequest.setAttribute()</code>,
162 * except that values can be changed and removed as well.
163 * <p>
164 * This is used by components to locate each other. A component, such as
165 * {@link org.apache.tapestry.html.Body}, will write itself under a well-known name into the
166 * request cycle, and components it wraps can locate it by that name.
167 * <p>
168 * Attributes are cleared at the end of each render or rewind phase.
169 */
170
171 public void setAttribute(String name, Object value);
172
173 /**
174 * Invoked just before rendering the response page to get all
175 * {@link org.apache.tapestry.engine.IPageRecorder page recorders}touched in this request cycle
176 * to commit their changes (save them to persistant storage).
177 *
178 * @see org.apache.tapestry.engine.IPageRecorder#commit()
179 */
180
181 public void commitPageChanges();
182
183 /**
184 * Returns the service which initiated this request cycle.
185 *
186 * @since 1.0.1
187 */
188
189 public IEngineService getService();
190
191 /**
192 * Used by {@link IForm forms}to perform a <em>partial</em> rewind so as to respond to the
193 * form submission (using the direct service).
194 * <p>
195 * Note: the targetActionId parameter was removed in release 4.0.
196 *
197 * @since 1.0.2
198 */
199
200 public void rewindForm(IForm form);
201
202 /**
203 * Much like {@link #forgetPage(String)}, but the page stays active and can even record
204 * changes, until the end of the request cycle, at which point it is discarded (and any recorded
205 * changes are lost). This is used in certain rare cases where a page has persistent state but
206 * is being renderred "for the last time".
207 *
208 * @since 2.0.2
209 * @deprecated To be removed in 4.1. Use {@link #forgetPage(String)}.
210 */
211
212 public void discardPage(String name);
213
214 /**
215 * Invoked by a {@link IEngineService service} to store an array of application-specific
216 * parameters. These can later be retrieved (typically, by an application-specific listener
217 * method) by invoking {@link #getServiceParameters()}.
218 * <p>
219 * Through release 2.1, parameters was of type String[]. This is an incompatible change in 2.2.
220 *
221 * @see org.apache.tapestry.engine.DirectService
222 * @since 2.0.3
223 * @deprecated To be removed in 4.1. Use {@link #setListenerParameters(Object[])}instead.
224 */
225
226 public void setServiceParameters(Object[] parameters);
227
228 /**
229 * Invoked by a {@link IEngineService service} to store an array of application-specific
230 * parameters. These can later be retrieved (typically, by an application-specific listener
231 * method) by invoking {@link #getListenerParameters()}.
232 *
233 * @see org.apache.tapestry.engine.DirectService
234 * @since 4.0
235 */
236 public void setListenerParameters(Object[] parameters);
237
238 /**
239 * Returns parameters previously stored by {@link #setServiceParameters(Object[])}.
240 * <p>
241 * Through release 2.1, the return type was String[]. This is an incompatible change in 2.2.
242 *
243 * @since 2.0.3
244 * @deprecated To be removed in 4.1. Use {@link #getListenerParameters()}instead.
245 */
246
247 public Object[] getServiceParameters();
248
249 /**
250 * Returns parameters previously stored by {@link #setListenerParameters(Object[])}.
251 *
252 * @since 4.0
253 */
254
255 public Object[] getListenerParameters();
256
257 /**
258 * A convienience for invoking {@link #activate(IPage)}. Invokes {@link #getPage(String)}to
259 * get an instance of the named page.
260 *
261 * @since 3.0
262 */
263
264 public void activate(String name);
265
266 /**
267 * Sets the active page for the request. The active page is the page which will ultimately
268 * render the response. The activate page is typically set by the {@link IEngineService service}.
269 * Frequently, the active page is changed (from a listener method) to choose an alternate page
270 * to render the response).
271 * <p>
272 * {@link IPage#validate(IRequestCycle)}is invoked on the page to be activated.
273 * {@link PageRedirectException}is caught and the page specified in the exception will be the
274 * active page instead (that is, a page may "pass the baton" to another page using the
275 * exception). The new page is also validated. This continues until a page does not throw
276 * {@link PageRedirectException}.
277 * <p>
278 * Validation loops can occur, where page A redirects to page B and then page B redirects back
279 * to page A (possibly with intermediate steps). This is detected and results in an
280 * {@link ApplicationRuntimeException}.
281 *
282 * @since 3.0
283 */
284 public void activate(IPage page);
285
286 /**
287 * Returns a query parameter value, or null if not provided in the request. If multiple values
288 * are provided, returns the first value.
289 *
290 * @since 4.0
291 */
292 public String getParameter(String name);
293
294 /**
295 * Returns all query parameter values for the given name. Returns null if no values were
296 * provided.
297 *
298 * @since 4.0
299 */
300 public String[] getParameters(String name);
301
302 /**
303 * Converts a partial URL into an absolute URL. Prefixes the provided URL with servlet context
304 * path (if any), then expands it to a full URL by prepending with the scheme, server and port
305 * (determined from the current {@link org.apache.tapestry.web.WebRequest request}.
306 *
307 * @since 4.0
308 */
309
310 public String getAbsoluteURL(String partialURL);
311
312 /**
313 * Forgets any stored changes to the specified page. If the page has already been loaded (and
314 * rolled back) then the loaded page instance is not affected; if the page is only loaded
315 * subsequently, the page instance will not see any persisted property changes.
316 *
317 * @since 4.0
318 */
319
320 public void forgetPage(String name);
321
322 /**
323 * Returns the central {@link org.apache.tapestry.services.Infrastructure} object used to
324 * manage the processing of the request.
325 *
326 * @since 4.0
327 */
328
329 public Infrastructure getInfrastructure();
330
331 /**
332 * Returns the {@link RequestContext}. This is provided to ease the upgrade from Tapestry 3.0.
333 *
334 * @deprecated To be removed in 4.1.
335 */
336
337 public RequestContext getRequestContext();
338
339 /**
340 * Returns the provided string, possibly modified (with an appended suffix) to make it unique.
341 *
342 * @param baseId
343 * the base id from which to generate the unique string.
344 * @return baseId, or baseId with a suffix appended (if the method has been previously invoked
345 * with the same baseId).
346 */
347
348 public String getUniqueId(String baseId);
349
350 /**
351 * Sends a redirect to the client web browser. This is currently a convinience for constructing
352 * and throwing a {@link RedirectException}, but may change in a later release.
353 *
354 * @since 4.0
355 * @throws RedirectException
356 */
357
358 public void sendRedirect(String URL);
359 }