View Javadoc

1   /*
2    * $Id: ExecuteAndWaitInterceptor.java 722961 2008-12-03 16:38:57Z musachy $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  
22  package org.apache.struts2.interceptor;
23  
24  import java.util.Collections;
25  import java.util.Map;
26  
27  import com.opensymphony.xwork2.ActionContext;
28  import com.opensymphony.xwork2.ActionInvocation;
29  import com.opensymphony.xwork2.ActionProxy;
30  import com.opensymphony.xwork2.config.entities.ResultConfig;
31  import com.opensymphony.xwork2.interceptor.MethodFilterInterceptor;
32  import com.opensymphony.xwork2.util.logging.Logger;
33  import com.opensymphony.xwork2.util.logging.LoggerFactory;
34  import org.apache.struts2.util.TokenHelper;
35  import org.apache.struts2.ServletActionContext;
36  
37  import javax.servlet.http.HttpSession;
38  
39  
40  /***
41   * <!-- START SNIPPET: description -->
42   *
43   * The ExecuteAndWaitInterceptor is great for running long-lived actions in the background while showing the user a nice
44   * progress meter. This also prevents the HTTP request from timing out when the action takes more than 5 or 10 minutes.
45   *
46   * <p/> Using this interceptor is pretty straight forward. Assuming that you are including struts-default.xml, this
47   * interceptor is already configured but is not part of any of the default stacks. Because of the nature of this
48   * interceptor, it must be the <b>last</b> interceptor in the stack.
49   *
50   * <p/> This interceptor works on a per-session basis. That means that the same action name (myLongRunningAction, in the
51   * above example) cannot be run more than once at a time in a given session. On the initial request or any subsequent
52   * requests (before the action has completed), the <b>wait</b> result will be returned. <b>The wait result is
53   * responsible for issuing a subsequent request back to the action, giving the effect of a self-updating progress
54   * meter</b>.
55   *
56   * <p/> If no "wait" result is found, Struts will automatically generate a wait result on the fly. This result is
57   * written in FreeMarker and cannot run unless FreeMarker is installed. If you don't wish to deploy with FreeMarker, you
58   * must provide your own wait result. This is generally a good thing to do anyway, as the default wait page is very
59   * plain.
60   *
61   * <p/>Whenever the wait result is returned, the <b>action that is currently running in the background will be placed on
62   * top of the stack</b>. This allows you to display progress data, such as a count, in the wait page. By making the wait
63   * page automatically reload the request to the action (which will be short-circuited by the interceptor), you can give
64   * the appearance of an automatic progress meter.
65   *
66   * <p/>This interceptor also supports using an initial wait delay. An initial delay is a time in milliseconds we let the
67   * server wait before the wait page is shown to the user. During the wait this interceptor will wake every 100 millis
68   * to check if the background process is done premature, thus if the job for some reason doesn't take to long the wait
69   * page is not shown to the user.
70   * <br/> This is useful for e.g. search actions that have a wide span of execution time. Using a delay time of 2000
71   * millis we ensure the user is presented fast search results immediately and for the slow results a wait page is used.
72   *
73   * <p/><b>Important</b>: Because the action will be running in a seperate thread, you can't use ActionContext because it
74   * is a ThreadLocal. This means if you need to access, for example, session data, you need to implement SessionAware
75   * rather than calling ActionContext.getSession().
76   *
77   * <p/>The thread kicked off by this interceptor will be named in the form <b><u>actionName</u>BackgroundProcess</b>.
78   * For example, the <i>search</i> action would run as a thread named <i>searchBackgroundProcess</i>.
79   *
80   * <!-- END SNIPPET: description -->
81   *
82   * <p/> <u>Interceptor parameters:</u>
83   *
84   * <!-- START SNIPPET: parameters -->
85   *
86   * <ul>
87   *
88   * <li>threadPriority (optional) - the priority to assign the thread. Default is <code>Thread.NORM_PRIORITY</code>.</li>
89   * <li>delay (optional) - an initial delay in millis to wait before the wait page is shown (returning <code>wait</code> as result code). Default is no initial delay.</li>
90   * <li>delaySleepInterval (optional) - only used with delay. Used for waking up at certain intervals to check if the background process is already done. Default is 100 millis.</li>
91   *
92   * </ul>
93   *
94   * <!-- END SNIPPET: parameters -->
95   *
96   * <p/> <u>Extending the interceptor:</u>
97   *
98   * <p/>
99   *
100  * <!-- START SNIPPET: extending -->
101  *
102  * If you wish to make special preparations before and/or after the invocation of the background thread, you can extend
103  * the BackgroundProcess class and implement the beforeInvocation() and afterInvocation() methods. This may be useful
104  * for obtaining and releasing resources that the background process will need to execute successfully. To use your
105  * background process extension, extend ExecuteAndWaitInterceptor and implement the getNewBackgroundProcess() method.
106  *
107  * <!-- END SNIPPET: extending -->
108  *
109  * <p/> <u>Example code:</u>
110  *
111  * <pre>
112  * <!-- START SNIPPET: example -->
113  * &lt;action name="someAction" class="com.examples.SomeAction"&gt;
114  *     &lt;interceptor-ref name="completeStack"/&gt;
115  *     &lt;interceptor-ref name="execAndWait"/&gt;
116  *     &lt;result name="wait"&gt;longRunningAction-wait.jsp&lt;/result&gt;
117  *     &lt;result name="success"&gt;longRunningAction-success.jsp&lt;/result&gt;
118  * &lt;/action&gt;
119  *
120  * &lt;%@ taglib prefix="s" uri="/struts" %&gt;
121  * &lt;html&gt;
122  *   &lt;head&gt;
123  *     &lt;title&gt;Please wait&lt;/title&gt;
124  *     &lt;meta http-equiv="refresh" content="5;url=&lt;s:url includeParams="all" /&gt;"/&gt;
125  *   &lt;/head&gt;
126  *   &lt;body&gt;
127  *     Please wait while we process your request.
128  *     Click &lt;a href="&lt;s:url includeParams="all" /&gt;">&lt;/a&gt; if this page does not reload automatically.
129  *   &lt;/body&gt;
130  * &lt;/html&gt;
131  * </pre>
132  *
133  * <p/> <u>Example code2:</u>
134  * This example will wait 2 second (2000 millis) before the wait page is shown to the user. Therefore
135  * if the long process didn't last long anyway the user isn't shown a wait page.
136  *
137  * <pre>
138  * &lt;action name="someAction" class="com.examples.SomeAction"&gt;
139  *     &lt;interceptor-ref name="completeStack"/&gt;
140  *     &lt;interceptor-ref name="execAndWait"&gt;
141  *         &lt;param name="delay"&gt;2000&lt;param&gt;
142  *     &lt;interceptor-ref&gt;
143  *     &lt;result name="wait"&gt;longRunningAction-wait.jsp&lt;/result&gt;
144  *     &lt;result name="success"&gt;longRunningAction-success.jsp&lt;/result&gt;
145  * &lt;/action&gt;
146  * </pre>
147  *
148  * <p/> <u>Example code3:</u>
149  * This example will wait 1 second (1000 millis) before the wait page is shown to the user.
150  * And at every 50 millis this interceptor will check if the background process is done, if so
151  * it will return before the 1 second has elapsed, and the user isn't shown a wait page.
152  *
153  * <pre>
154  * &lt;action name="someAction" class="com.examples.SomeAction"&gt;
155  *     &lt;interceptor-ref name="completeStack"/&gt;
156  *     &lt;interceptor-ref name="execAndWait"&gt;
157  *         &lt;param name="delay"&gt;1000&lt;param&gt;
158  *         &lt;param name="delaySleepInterval"&gt;50&lt;param&gt;
159  *     &lt;interceptor-ref&gt;
160  *     &lt;result name="wait"&gt;longRunningAction-wait.jsp&lt;/result&gt;
161  *     &lt;result name="success"&gt;longRunningAction-success.jsp&lt;/result&gt;
162  * &lt;/action&gt;
163  * </pre>
164  *
165  * <!-- END SNIPPET: example -->
166  *
167  */
168 public class ExecuteAndWaitInterceptor extends MethodFilterInterceptor {
169 
170     private static final long serialVersionUID = -2754639196749652512L;
171 
172     private static final Logger LOG = LoggerFactory.getLogger(ExecuteAndWaitInterceptor.class);
173 
174     public static final String KEY = "__execWait";
175     public static final String WAIT = "wait";
176     protected int delay;
177     protected int delaySleepInterval = 100; // default sleep 100 millis before checking if background process is done
178     protected boolean executeAfterValidationPass = false;
179 
180     private int threadPriority = Thread.NORM_PRIORITY;
181 
182     /* (non-Javadoc)
183      * @see com.opensymphony.xwork2.interceptor.Interceptor#init()
184      */
185     public void init() {
186     }
187 
188     /***
189      * Creates a new background process
190      *
191      * @param name The process name
192      * @param actionInvocation The action invocation
193      * @param threadPriority The thread priority
194      * @return The new process
195      */
196     protected BackgroundProcess getNewBackgroundProcess(String name, ActionInvocation actionInvocation, int threadPriority) {
197         return new BackgroundProcess(name + "BackgroundThread", actionInvocation, threadPriority);
198     }
199 
200     /***
201      * Returns the name to associate the background process.  Override to change the way background processes
202      * are mapped to requests.
203      *
204      * @return the name of the background thread
205      */
206     protected String getBackgroundProcessName(ActionProxy proxy) {
207         return proxy.getActionName();
208     }
209 
210     /* (non-Javadoc)
211      * @see com.opensymphony.xwork2.interceptor.MethodFilterInterceptor#doIntercept(com.opensymphony.xwork2.ActionInvocation)
212      */
213     protected String doIntercept(ActionInvocation actionInvocation) throws Exception {
214         ActionProxy proxy = actionInvocation.getProxy();
215         String name = getBackgroundProcessName(proxy);
216         ActionContext context = actionInvocation.getInvocationContext();
217         Map session = context.getSession();
218         HttpSession httpSession = ServletActionContext.getRequest().getSession(true);
219 
220         Boolean secondTime  = true;
221         if (executeAfterValidationPass) {
222             secondTime = (Boolean) context.get(KEY);
223             if (secondTime == null) {
224                 context.put(KEY, true);
225                 secondTime = false;
226             } else {
227                 secondTime = true;
228                 context.put(KEY, null);
229             }
230         }
231 
232         //sync on the real HttpSession as the session from the context is a wrap that is created
233         //on every request
234         synchronized (httpSession) {
235             BackgroundProcess bp = (BackgroundProcess) session.get(KEY + name);
236 
237             if ((!executeAfterValidationPass || secondTime) && bp == null) {
238                 bp = getNewBackgroundProcess(name, actionInvocation, threadPriority);
239                 session.put(KEY + name, bp);
240                 performInitialDelay(bp); // first time let some time pass before showing wait page
241                 secondTime = false;
242             }
243 
244             if ((!executeAfterValidationPass || !secondTime) && bp != null && !bp.isDone()) {
245                 actionInvocation.getStack().push(bp.getAction());
246                 Map results = proxy.getConfig().getResults();
247                 if (!results.containsKey(WAIT)) {
248                     LOG.warn("ExecuteAndWait interceptor has detected that no result named 'wait' is available. " +
249                             "Defaulting to a plain built-in wait page. It is highly recommend you " +
250                             "provide an action-specific or global result named '" + WAIT +
251                             "'! This requires FreeMarker support and won't work if you don't have it installed");
252                     // no wait result? hmm -- let's try to do dynamically put it in for you!
253                     ResultConfig rc = new ResultConfig.Builder(WAIT, "org.apache.struts2.views.freemarker.FreemarkerResult")
254                             .addParams(Collections.singletonMap("location", "/org/apache/struts2/interceptor/wait.ftl"))
255                             .build();
256                     results.put(WAIT, rc);
257                 }
258 
259                 if (TokenHelper.getToken() != null) {
260                     session.put(TokenHelper.getTokenName(), TokenHelper.getToken());
261                 }
262 
263                 return WAIT;
264             } else if ((!executeAfterValidationPass || !secondTime) && bp != null && bp.isDone()) {
265                 session.remove(KEY + name);
266                 actionInvocation.getStack().push(bp.getAction());
267 
268                 // if an exception occured during action execution, throw it here
269                 if (bp.getException() != null) {
270                     throw bp.getException();
271                 }
272 
273                 return bp.getResult();
274             } else {
275                 // this is the first instance of the interceptor and there is no existing action
276                 // already run in the background, so let's just let this pass through. We assume
277                 // the action invocation will be run in the background on the subsequent pass through
278                 // this interceptor
279                 return actionInvocation.invoke();
280             }
281         }
282     }
283 
284 
285     /* (non-Javadoc)
286      * @see com.opensymphony.xwork2.interceptor.Interceptor#destroy()
287      */
288     public void destroy() {
289     }
290 
291     /***
292      * Performs the initial delay.
293      * <p/>
294      * When this interceptor is executed for the first time this methods handles any provided initial delay.
295      * An initial delay is a time in miliseconds we let the server wait before we continue.
296      * <br/> During the wait this interceptor will wake every 100 millis to check if the background
297      * process is done premature, thus if the job for some reason doesn't take to long the wait
298      * page is not shown to the user.
299      *
300      * @param bp the background process
301      * @throws InterruptedException is thrown by Thread.sleep
302      */
303     protected void performInitialDelay(BackgroundProcess bp) throws InterruptedException {
304         if (delay <= 0 || delaySleepInterval <= 0) {
305             return;
306         }
307 
308         int steps = delay / delaySleepInterval;
309         if (LOG.isDebugEnabled()) {
310             LOG.debug("Delaying for " + delay + " millis. (using " + steps + " steps)");
311         }
312         int step;
313         for (step = 0; step < steps && !bp.isDone(); step++) {
314             Thread.sleep(delaySleepInterval);
315         }
316         if (LOG.isDebugEnabled()) {
317             LOG.debug("Sleeping ended after " + step + " steps and the background process is " + (bp.isDone() ? " done" : " not done"));
318         }
319     }
320 
321     /***
322      * Sets the thread priority of the background process.
323      *
324      * @param threadPriority the priority from <code>Thread.XXX</code>
325      */
326     public void setThreadPriority(int threadPriority) {
327         this.threadPriority = threadPriority;
328     }
329 
330     /***
331      * Sets the initial delay in millis (msec).
332      *
333      * @param delay in millis. (0 for not used)
334      */
335     public void setDelay(int delay) {
336         this.delay = delay;
337     }
338 
339     /***
340      * Sets the sleep interval in millis (msec) when performing the initial delay.
341      *
342      * @param delaySleepInterval in millis (0 for not used)
343      */
344     public void setDelaySleepInterval(int delaySleepInterval) {
345         this.delaySleepInterval = delaySleepInterval;
346     }
347 
348     /***
349      * Whether to start the background process after the second pass (first being validation)
350      * or not
351      *
352      * @param executeAfterValidationPass the executeAfterValidationPass to set
353      */
354     public void setExecuteAfterValidationPass(boolean executeAfterValidationPass) {
355         this.executeAfterValidationPass = executeAfterValidationPass;
356     }
357 
358 
359 }