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1   /*
2    * $Id: ScopeInterceptor.java 678526 2008-07-21 18:54:57Z 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.io.Serializable;
25  import java.util.IdentityHashMap;
26  import java.util.Map;
27  
28  import org.apache.struts2.ServletActionContext;
29  import org.apache.struts2.StrutsException;
30  import org.apache.struts2.dispatcher.SessionMap;
31  
32  import com.opensymphony.xwork2.ActionContext;
33  import com.opensymphony.xwork2.ActionInvocation;
34  import com.opensymphony.xwork2.ActionProxy;
35  import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
36  import com.opensymphony.xwork2.interceptor.PreResultListener;
37  import com.opensymphony.xwork2.util.ValueStack;
38  import com.opensymphony.xwork2.util.logging.Logger;
39  import com.opensymphony.xwork2.util.logging.LoggerFactory;
40  
41  /***
42   * <!-- START SNIPPET: description -->
43   *
44   * This is designed to solve a few simple issues related to wizard-like functionality in Struts. One of those issues is
45   * that some applications have a application-wide parameters commonly used, such <i>pageLen</i> (used for records per
46   * page). Rather than requiring that each action check if such parameters are supplied, this interceptor can look for
47   * specified parameters and pull them out of the session.
48   *
49   * <p/> This works by setting listed properties at action start with values from session/application attributes keyed
50   * after the action's class, the action's name, or any supplied key. After action is executed all the listed properties
51   * are taken back and put in session or application context.
52   *
53   * <p/> To make sure that each execution of the action is consistent it makes use of session-level locking. This way it
54   * guarantees that each action execution is atomic at the session level. It doesn't guarantee application level
55   * consistency however there has yet to be enough reasons to do so. Application level consistency would also be a big
56   * performance overkill.
57   *
58   * <p/> Note that this interceptor takes a snapshot of action properties just before result is presented (using a {@link
59   * PreResultListener}), rather than after action is invoked. There is a reason for that: At this moment we know that
60   * action's state is "complete" as it's values may depend on the rest of the stack and specifically - on the values of
61   * nested interceptors.
62   *
63   * <!-- END SNIPPET: description -->
64   *
65   * <p/> <u>Interceptor parameters:</u>
66   *
67   * <!-- START SNIPPET: parameters -->
68   *
69   * <ul>
70   *
71   * <li>session - a list of action properties to be bound to session scope</li>
72   *
73   * <li>application - a list of action properties to be bound to application scope</li>
74   *
75   * <li>key - a session/application attribute key prefix, can contain following values:</li>
76   *
77   * <ul>
78   *
79   * <li>CLASS - that creates a unique key prefix based on action namespace and action class, it's a default value</li>
80   *
81   * <li>ACTION - creates a unique key prefix based on action namespace and action name</li>
82   *
83   * <li>any other value is taken literally as key prefix</li>
84   *
85   * </ul>
86   *
87   * <li>type - with one of the following</li>
88   *
89   * <ul>
90   *
91   * <li>start - means it's a start action of the wizard-like action sequence and all session scoped properties are reset
92   * to their defaults</li>
93   *
94   * <li>end - means that session scoped properties are removed from session after action is run</li>
95   *
96   * <li>any other value or no value means that it's in-the-middle action that is set with session properties before it's
97   * executed, and it's properties are put back to session after execution</li>
98   *
99   * </ul>
100  *
101  * <li>sessionReset - name of a parameter (defaults to 'session.reset') which if set, causes all session values to be reset to action's default values or application
102  * scope values, note that it is similar to type="start" and in fact it does the same, but in our team it is sometimes
103  * semantically preferred. We use session scope in two patterns - sometimes there are wizard-like action sequences that
104  * have start and end, and sometimes we just want simply reset current session values.</li>
105  *
106  * <li>reset - boolean, defaults to false, if set, it has the same effect as setting all session values to be reset to action's default values or application.</li>
107  *
108  * <li>autoCreateSession - boolean value, sets if the session should be automatically created.</li>
109  * </ul>
110  *
111  * <!-- END SNIPPET: parameters -->
112  *
113  * <p/> <u>Extending the interceptor:</u>
114  *
115  * <p/>
116  *
117  * <!-- START SNIPPET: extending -->
118  *
119  * There are no know extension points for this interceptor.
120  *
121  * <!-- END SNIPPET: extending -->
122  *
123  * <p/> <u>Example code:</u>
124  *
125  * <pre>
126  * <!-- START SNIPPET: example -->
127  * &lt;!-- As the filter and orderBy parameters are common for all my browse-type actions,
128  *      you can move control to the scope interceptor. In the session parameter you can list
129  *      action properties that are going to be automatically managed over session. You can
130  *      do the same for application-scoped variables--&gt;
131  * &lt;action name="someAction" class="com.examples.SomeAction"&gt;
132  *     &lt;interceptor-ref name="basicStack"/&gt;
133  *     &lt;interceptor-ref name="hibernate"/&gt;
134  *     &lt;interceptor-ref name="scope"&gt;
135  *         &lt;param name="session"&gt;filter,orderBy&lt;/param&gt;
136  *         &lt;param name="autoCreateSession"&gt;true&lt;/param&gt;
137  *     &lt;/interceptor-ref&gt;
138  *     &lt;result name="success"&gt;good_result.ftl&lt;/result&gt;
139  * &lt;/action&gt;
140  * <!-- END SNIPPET: example -->
141  * </pre>
142  *
143  */
144 public class ScopeInterceptor extends AbstractInterceptor implements PreResultListener {
145 
146     private static final long serialVersionUID = 9120762699600054395L;
147 
148     private static final Logger LOG = LoggerFactory.getLogger(ScopeInterceptor.class);
149 
150     private String[] application = null;
151     private String[] session = null;
152     private String key;
153     private String type = null;
154     private boolean autoCreateSession = true;
155     private String sessionReset = "session.reset";
156     private boolean reset = false;
157 
158     /***
159      * Sets a list of application scoped properties
160      *
161      * @param s A comma-delimited list
162      */
163     public void setApplication(String s) {
164         if (s != null) {
165             application = s.split(" *, *");
166         }
167     }
168 
169     /***
170      * Sets a list of session scoped properties
171      *
172      * @param s A comma-delimited list
173      */
174     public void setSession(String s) {
175         if (s != null) {
176             session = s.split(" *, *");
177         }
178     }
179 
180     /***
181      * Sets if the session should be automatically created
182      *
183      * @param value True if it should be created
184      */
185     public void setAutoCreateSession(String value) {
186         if (value != null && value.length() > 0) {
187             this.autoCreateSession = Boolean.valueOf(value).booleanValue();
188         }
189     }
190 
191     private String getKey(ActionInvocation invocation) {
192         ActionProxy proxy = invocation.getProxy();
193         if (key == null || "CLASS".equals(key)) {
194             return "struts.ScopeInterceptor:" + proxy.getAction().getClass();
195         } else if ("ACTION".equals(key)) {
196             return "struts.ScopeInterceptor:" + proxy.getNamespace() + ":" + proxy.getActionName();
197         }
198         return key;
199     }
200 
201     /***
202      * The constructor
203      */
204     public ScopeInterceptor() {
205         super();
206     }
207 
208     // Since 2.0.7. Avoid null references on session serialization (WW-1803).
209     private static class NULLClass implements Serializable {
210       public String toString() {
211         return "NULL";
212       }
213       public boolean equals(Object obj) {
214         return obj == null || (obj instanceof NULLClass);
215       }
216     }
217 
218     private static final Object NULL = new NULLClass();
219 
220     private static final Object nullConvert(Object o) {
221         if (o == null) {
222             return NULL;
223         }
224 
225         if (o == NULL || NULL.equals(o)) {
226             return null;
227         }
228 
229         return o;
230     }
231 
232     private static Map locks = new IdentityHashMap();
233 
234     static final void lock(Object o, ActionInvocation invocation) throws Exception {
235         synchronized (o) {
236             int count = 3;
237             Object previous = null;
238             while ((previous = locks.get(o)) != null) {
239                 if (previous == invocation) {
240                     return;
241                 }
242                 if (count-- <= 0) {
243                     locks.remove(o);
244                     o.notify();
245 
246                     throw new StrutsException("Deadlock in session lock");
247                 }
248                 o.wait(10000);
249             }
250             ;
251             locks.put(o, invocation);
252         }
253     }
254 
255     static final void unlock(Object o) {
256         synchronized (o) {
257             locks.remove(o);
258             o.notify();
259         }
260     }
261 
262     protected void after(ActionInvocation invocation, String result) throws Exception {
263         Map ses = ActionContext.getContext().getSession();
264         if ( ses != null) {
265             unlock(ses);
266         }
267     }
268 
269 
270     protected void before(ActionInvocation invocation) throws Exception {
271         invocation.addPreResultListener(this);
272         Map ses = ActionContext.getContext().getSession();
273         if (ses == null && autoCreateSession) {
274             ses = new SessionMap(ServletActionContext.getRequest());
275             ActionContext.getContext().setSession(ses);
276         }
277 
278         if ( ses != null) {
279             lock(ses, invocation);
280         }
281 
282         String key = getKey(invocation);
283         Map app = ActionContext.getContext().getApplication();
284         final ValueStack stack = ActionContext.getContext().getValueStack();
285 
286         if (LOG.isDebugEnabled()) {
287             LOG.debug("scope interceptor before");
288         }
289 
290         if (application != null)
291             for (int i = 0; i < application.length; i++) {
292                 String string = application[i];
293                 Object attribute = app.get(key + string);
294                 if (attribute != null) {
295                     if (LOG.isDebugEnabled()) {
296                         LOG.debug("application scoped variable set " + string + " = " + String.valueOf(attribute));
297                     }
298 
299                     stack.setValue(string, nullConvert(attribute));
300                 }
301             }
302 
303         if (ActionContext.getContext().getParameters().get(sessionReset) != null) {
304             return;
305         }
306 
307         if (reset) {
308             return;
309         }
310 
311         if (ses == null) {
312             LOG.debug("No HttpSession created... Cannot set session scoped variables");
313             return;
314         }
315 
316         if (session != null && (!"start".equals(type))) {
317             for (int i = 0; i < session.length; i++) {
318                 String string = session[i];
319                 Object attribute = ses.get(key + string);
320                 if (attribute != null) {
321                     if (LOG.isDebugEnabled()) {
322                         LOG.debug("session scoped variable set " + string + " = " + String.valueOf(attribute));
323                     }
324                     stack.setValue(string, nullConvert(attribute));
325                 }
326             }
327         }
328     }
329 
330     public void setKey(String key) {
331         this.key = key;
332     }
333 
334     /* (non-Javadoc)
335      * @see com.opensymphony.xwork2.interceptor.PreResultListener#beforeResult(com.opensymphony.xwork2.ActionInvocation, java.lang.String)
336      */
337     public void beforeResult(ActionInvocation invocation, String resultCode) {
338         String key = getKey(invocation);
339         Map app = ActionContext.getContext().getApplication();
340         final ValueStack stack = ActionContext.getContext().getValueStack();
341 
342         if (application != null)
343             for (int i = 0; i < application.length; i++) {
344                 String string = application[i];
345                 Object value = stack.findValue(string);
346                 if (LOG.isDebugEnabled()) {
347                     LOG.debug("application scoped variable saved " + string + " = " + String.valueOf(value));
348                 }
349 
350                 //if( value != null)
351                 app.put(key + string, nullConvert(value));
352             }
353 
354         boolean ends = "end".equals(type);
355 
356         Map ses = ActionContext.getContext().getSession();
357         if (ses != null) {
358 
359             if (session != null) {
360                 for (int i = 0; i < session.length; i++) {
361                     String string = session[i];
362                     if (ends) {
363                         ses.remove(key + string);
364                     } else {
365                         Object value = stack.findValue(string);
366 
367                         if (LOG.isDebugEnabled()) {
368                             LOG.debug("session scoped variable saved " + string + " = " + String.valueOf(value));
369                         }
370 
371                         // Null value should be scoped too
372                         //if( value != null)
373                         ses.put(key + string, nullConvert(value));
374                     }
375                 }
376             }
377             unlock(ses);
378         } else {
379             LOG.debug("No HttpSession created... Cannot save session scoped variables.");
380         }
381         if (LOG.isDebugEnabled()) {
382             LOG.debug("scope interceptor after (before result)");
383         }
384     }
385 
386     /***
387      * @return The type of scope operation, "start" or "end"
388      */
389     public String getType() {
390         return type;
391     }
392 
393     /***
394      * Sets the type of scope operation
395      *
396      * @param type Either "start" or "end"
397      */
398     public void setType(String type) {
399         type = type.toLowerCase();
400         if ("start".equals(type) || "end".equals(type)) {
401             this.type = type;
402         } else {
403             throw new IllegalArgumentException("Only start or end are allowed arguments for type");
404         }
405     }
406 
407     /***
408      * @return Gets the session reset parameter name
409      */
410     public String getSessionReset() {
411         return sessionReset;
412     }
413 
414     /***
415      * @param sessionReset The session reset parameter name
416      */
417     public void setSessionReset(String sessionReset) {
418         this.sessionReset = sessionReset;
419     }
420 
421     /* (non-Javadoc)
422      * @see com.opensymphony.xwork2.interceptor.Interceptor#intercept(com.opensymphony.xwork2.ActionInvocation)
423      */
424     public String intercept(ActionInvocation invocation) throws Exception {
425         String result = null;
426         Map ses = ActionContext.getContext().getSession();
427         before(invocation);
428         try {
429             result = invocation.invoke();
430             after(invocation, result);
431         } finally {
432             if (ses != null) {
433                 unlock(ses);
434             }
435         }
436 
437         return result;
438     }
439 
440     /***
441      * @return True if the scope is reset
442      */
443     public boolean isReset() {
444         return reset;
445     }
446 
447     /***
448      * @param reset True if the scope should be reset
449      */
450     public void setReset(boolean reset) {
451         this.reset = reset;
452     }
453 }