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    
094        public String getNextActionId();
095    
096        /**
097         * Identifies the active page, the page which will ultimately render the response.
098         */
099    
100        public IPage getPage();
101    
102        /**
103         * Returns the page with the given name. If the page has been previously loaded in the current
104         * request cycle, that page is returned. Otherwise, the engine's page loader is used to load the
105         * page.
106         * 
107         * @throws PageNotFoundException
108         *             if the page does not exist.
109         * @see org.apache.tapestry.engine.IPageSource#getPage(IRequestCycle, String, IMonitor)
110         */
111    
112        public IPage getPage(String name);
113    
114        /**
115         * Returns true if the context is being used to rewind a prior state of the page. This is only
116         * true when there is a target action id.
117         */
118    
119        public boolean isRewinding();
120    
121        /**
122         * Checks to see if the current action id matches the target action id. Returns true only if
123         * they match. Returns false if there is no target action id (that is, during page rendering).
124         * <p>
125         * If theres a match on action id, then the component is compared against the target component.
126         * If there's a mismatch then a {@link StaleLinkException}is thrown.
127         */
128    
129        public boolean isRewound(IComponent component) throws StaleLinkException;
130    
131        /**
132         * Removes a previously stored attribute, if one with the given name exists.
133         */
134    
135        public void removeAttribute(String name);
136    
137        /**
138         * Renders the given page. Applications should always use this method to render the page, rather
139         * than directly invoking {@link IPage#render(IMarkupWriter, IRequestCycle)}since the request
140         * cycle must perform some setup before rendering.
141         */
142    
143        public void renderPage(IMarkupWriter writer);
144    
145        /**
146         * Rewinds a page and executes some form of action when the component with the specified action
147         * id is reached.
148         * 
149         * @see IAction
150         * @see org.apache.tapestry.link.ActionLink
151         */
152    
153        public void rewindPage(String targetActionId, IComponent targetComponent);
154    
155        /**
156         * Allows a temporary object to be stored in the request cycle, which allows otherwise unrelated
157         * objects to communicate. This is similar to <code>HttpServletRequest.setAttribute()</code>,
158         * except that values can be changed and removed as well.
159         * <p>
160         * This is used by components to locate each other. A component, such as
161         * {@link org.apache.tapestry.html.Body}, will write itself under a well-known name into the
162         * request cycle, and components it wraps can locate it by that name.
163         * <p>
164         * Attributes are cleared at the end of each render or rewind phase.
165         */
166    
167        public void setAttribute(String name, Object value);
168    
169        /**
170         * Invoked just before rendering the response page to get all
171         * {@link org.apache.tapestry.engine.IPageRecorder page recorders}touched in this request cycle
172         * to commit their changes (save them to persistant storage).
173         * 
174         * @see org.apache.tapestry.engine.IPageRecorder#commit()
175         */
176    
177        public void commitPageChanges();
178    
179        /**
180         * Returns the service which initiated this request cycle.
181         * 
182         * @since 1.0.1
183         */
184    
185        public IEngineService getService();
186    
187        /**
188         * Used by {@link IForm forms}to perform a <em>partial</em> rewind so as to respond to the
189         * form submission (using the direct service).
190         * <p>
191         * Note: the targetActionId parameter was removed in release 4.0.
192         * 
193         * @since 1.0.2
194         */
195    
196        public void rewindForm(IForm form);
197    
198        /**
199         * Much like {@link #forgetPage(String)}, but the page stays active and can even record
200         * changes, until the end of the request cycle, at which point it is discarded (and any recorded
201         * changes are lost). This is used in certain rare cases where a page has persistent state but
202         * is being renderred "for the last time".
203         * 
204         * @since 2.0.2
205         * @deprecated To be removed in 4.1. Use {@link #forgetPage(String)}.
206         */
207    
208        public void discardPage(String name);
209    
210        /**
211         * Invoked by a {@link IEngineService service}&nbsp;to store an array of application-specific
212         * parameters. These can later be retrieved (typically, by an application-specific listener
213         * method) by invoking {@link #getServiceParameters()}.
214         * <p>
215         * Through release 2.1, parameters was of type String[]. This is an incompatible change in 2.2.
216         * 
217         * @see org.apache.tapestry.engine.DirectService
218         * @since 2.0.3
219         * @deprecated To be removed in 4.1. Use {@link #setListenerParameters(Object[])}instead.
220         */
221    
222        public void setServiceParameters(Object[] parameters);
223    
224        /**
225         * Invoked by a {@link IEngineService service}&nbsp;to store an array of application-specific
226         * parameters. These can later be retrieved (typically, by an application-specific listener
227         * method) by invoking {@link #getListenerParameters()}.
228         * 
229         * @see org.apache.tapestry.engine.DirectService
230         * @since 4.0
231         */
232        public void setListenerParameters(Object[] parameters);
233    
234        /**
235         * Returns parameters previously stored by {@link #setServiceParameters(Object[])}.
236         * <p>
237         * Through release 2.1, the return type was String[]. This is an incompatible change in 2.2.
238         * 
239         * @since 2.0.3
240         * @deprecated To be removed in 4.1. Use {@link #getListenerParameters()}instead.
241         */
242    
243        public Object[] getServiceParameters();
244    
245        /**
246         * Returns parameters previously stored by {@link #setListenerParameters(Object[])}.
247         * 
248         * @since 4.0
249         */
250    
251        public Object[] getListenerParameters();
252    
253        /**
254         * A convienience for invoking {@link #activate(IPage)}. Invokes {@link #getPage(String)}to
255         * get an instance of the named page.
256         * 
257         * @since 3.0
258         */
259    
260        public void activate(String name);
261    
262        /**
263         * Sets the active page for the request. The active page is the page which will ultimately
264         * render the response. The activate page is typically set by the {@link IEngineService service}.
265         * Frequently, the active page is changed (from a listener method) to choose an alternate page
266         * to render the response).
267         * <p>
268         * {@link IPage#validate(IRequestCycle)}is invoked on the page to be activated.
269         * {@link PageRedirectException}is caught and the page specified in the exception will be the
270         * active page instead (that is, a page may "pass the baton" to another page using the
271         * exception). The new page is also validated. This continues until a page does not throw
272         * {@link PageRedirectException}.
273         * <p>
274         * Validation loops can occur, where page A redirects to page B and then page B redirects back
275         * to page A (possibly with intermediate steps). This is detected and results in an
276         * {@link ApplicationRuntimeException}.
277         * 
278         * @since 3.0
279         */
280        public void activate(IPage page);
281    
282        /**
283         * Returns a query parameter value, or null if not provided in the request. If multiple values
284         * are provided, returns the first value.
285         * 
286         * @since 4.0
287         */
288        public String getParameter(String name);
289    
290        /**
291         * Returns all query parameter values for the given name. Returns null if no values were
292         * provided.
293         * 
294         * @since 4.0
295         */
296        public String[] getParameters(String name);
297    
298        /**
299         * Converts a partial URL into an absolute URL. Prefixes the provided URL with servlet context
300         * path (if any), then expands it to a full URL by prepending with the scheme, server and port
301         * (determined from the current {@link org.apache.tapestry.web.WebRequest request}.
302         * 
303         * @since 4.0
304         */
305    
306        public String getAbsoluteURL(String partialURL);
307    
308        /**
309         * Forgets any stored changes to the specified page. If the page has already been loaded (and
310         * rolled back) then the loaded page instance is not affected; if the page is only loaded
311         * subsequently, the page instance will not see any persisted property changes.
312         * 
313         * @since 4.0
314         */
315    
316        public void forgetPage(String name);
317    
318        /**
319         * Returns the central {@link org.apache.tapestry.services.Infrastructure}&nbsp;object used to
320         * manage the processing of the request.
321         * 
322         * @since 4.0
323         */
324    
325        public Infrastructure getInfrastructure();
326    
327        /**
328         * Returns the {@link RequestContext}. This is provided to ease the upgrade from Tapestry 3.0.
329         * 
330         * @deprecated To be removed in 4.1.
331         */
332    
333        public RequestContext getRequestContext();
334    
335        /**
336         * Returns the provided string, possibly modified (with an appended suffix) to make it unique.
337         * 
338         * @param baseId
339         *            the base id from which to generate the unique string.
340         * @return baseId, or baseId with a suffix appended (if the method has been previously invoked
341         *         with the same baseId).
342         */
343    
344        public String getUniqueId(String baseId);
345    
346        /**
347         * Sends a redirect to the client web browser. This is currently a convinience for constructing
348         * and throwing a {@link RedirectException}, but may change in a later release.
349         * 
350         * @since 4.0
351         * @throws RedirectException
352         */
353    
354        public void sendRedirect(String URL);
355    }