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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   http://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  
20  package org.apache.myfaces.orchestra.conversation.spring;
21  
22  import java.util.HashMap;
23  import java.util.Map;
24  
25  import org.aopalliance.aop.Advice;
26  import org.apache.commons.logging.Log;
27  import org.apache.commons.logging.LogFactory;
28  import org.apache.myfaces.orchestra.conversation.Conversation;
29  import org.apache.myfaces.orchestra.conversation.ConversationAware;
30  import org.apache.myfaces.orchestra.conversation.ConversationBindingEvent;
31  import org.apache.myfaces.orchestra.conversation.ConversationBindingListener;
32  import org.apache.myfaces.orchestra.conversation.ConversationContext;
33  import org.apache.myfaces.orchestra.conversation.ConversationFactory;
34  import org.apache.myfaces.orchestra.conversation.ConversationManager;
35  import org.apache.myfaces.orchestra.conversation.CurrentConversationAdvice;
36  import org.apache.myfaces.orchestra.frameworkAdapter.FrameworkAdapter;
37  import org.apache.myfaces.orchestra.lib.jsf.PortletOrchestraFacesContextFactory;
38  import org.springframework.aop.Advisor;
39  import org.springframework.aop.SpringProxy;
40  import org.springframework.aop.framework.ProxyFactory;
41  import org.springframework.aop.framework.autoproxy.AutoProxyUtils;
42  import org.springframework.aop.scope.ScopedProxyFactoryBean;
43  import org.springframework.beans.BeansException;
44  import org.springframework.beans.factory.BeanFactory;
45  import org.springframework.beans.factory.BeanFactoryAware;
46  import org.springframework.beans.factory.ObjectFactory;
47  import org.springframework.beans.factory.config.BeanDefinition;
48  import org.springframework.beans.factory.config.BeanPostProcessor;
49  import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
50  import org.springframework.beans.factory.config.Scope;
51  import org.springframework.context.ApplicationContext;
52  import org.springframework.context.ApplicationContextAware;
53  import org.springframework.context.ConfigurableApplicationContext;
54  
55  /**
56   * Abstract basis class for all the Orchestra scopes.
57   * <p>
58   * A scope object has two quite different roles:
59   * <ol>
60   * <li>It handles the lookup of beans in a scope, and creates them if needed</li>
61   * <li>It handles the creation of Conversation objects, using the spring properties
62   * configured on the scope object.</li>
63   * </ol>
64   * <p>
65   * This base class handles item 1 above, and leaves item 2 to a subclass. The
66   * declaration of interface ConversationFactory needs to be on this class, however,
67   * as the createBean method needs to invoke it.
68   */
69  public abstract class AbstractSpringOrchestraScope implements
70      ConversationFactory, // Orchestra interfaces
71      Scope, BeanFactoryAware, ApplicationContextAware // Spring interfaces
72  {
73      private static final Advice[] NO_ADVICES = new Advice[0];
74      private static final String POST_PROCESSOR_BEAN_NAME =
75          AbstractSpringOrchestraScope.class.getName() + "_BeanPostProcessor";
76  
77      private final Log log = LogFactory.getLog(AbstractSpringOrchestraScope.class);
78  
79      private ConfigurableApplicationContext applicationContext;
80      private Advice[] advices;
81      private boolean autoProxy = true;
82  
83      public AbstractSpringOrchestraScope()
84      {
85      }
86  
87      /**
88       * The advices (interceptors) which will be applied to the conversation scoped bean.
89       * These are applied whenever a method is invoked on the bean [1].
90       * <p>
91       * An application's spring configuration uses this method to control what advices are
92       * applied to beans generated from this scope. One commonly applied advice is the
93       * Orchestra persistence interceptor, which ensures that whenever a method on a
94       * conversation-scoped bean is invoked the "global persistence context" is set
95       * to the context for the conversation that bean is in.
96       * <p>
97       * Note [1]: the advices are only applied when the bean is invoked via its proxy. If
98       * invoked via the "this" pointer of the object the interceptors will not run. This
99       * is generally a good thing, as they are not wanted when a method on the bean invokes
100      * another method on the same bean. However it is bad if the bean passes "this" as a
101      * parameter to some other object that makes a callback on it at some later time. In
102      * that case, the bean must take care to pass its proxy to the remote object, not
103      * itself. See method ConversationUtils.getCurrentBean().
104      */
105     public void setAdvices(Advice[] advices)
106     {
107         this.advices = advices;
108     }
109 
110     /**
111      * @since 1.1
112      */
113     protected Advice[] getAdvices()
114     {
115         return advices;
116     }
117 
118     /**
119      * Configuration for a scope object to control whether "scoped proxy" objects are
120      * automatically wrapped around each conversation bean.
121      * <p>
122      * Automatically applying scope proxies solves a lot of tricky problems with "stale"
123      * beans, and should generally be used. However it does require CGLIB to be present
124      * in the classpath. It also can impact performance in some cases. Where this is a
125      * problem, this flag can turn autoproxying off. Note that the standard spring
126      * aop:scoped-proxy bean can then be used on individual beans to re-enable
127      * proxying for specific beans if desired.
128      * <p>
129      * This defaults to true.
130      *
131      * @since 1.1
132      */
133     public void setAutoProxy(boolean state)
134     {
135         autoProxy = state;
136     }
137 
138     /**
139      * Return the conversation context id.
140      * <p>
141      * Note: This conversationId is something spring requires. It has nothing to do with the Orchestra
142      * conversation id.
143      * <p>
144      * TODO: what does Spring use this for????
145      */
146     public String getConversationId()
147     {
148         ConversationManager manager = ConversationManager.getInstance();
149         ConversationContext ctx = manager.getCurrentConversationContext();
150         if (ctx != null)
151         {
152             return Long.toString(ctx.getId(), 10);
153         }
154 
155         return null;
156     }
157 
158     /**
159      * This is invoked by Spring whenever someone calls getBean(name) on a bean-factory
160      * and the bean-definition for that bean has a scope attribute that maps to an
161      * instance of this class.
162      * <p>
163      * In the normal case, this method returns an internally-created proxy object
164      * that fetches the "real" bean every time a method is invoked on the proxy
165      * (see method getRealBean). This does obviously have some performance impact.
166      * However it is necessary when beans from one conversation are referencing beans
167      * from another conversation as the conversation lifetimes are not the same;
168      * without this proxying there are many cases where "stale" references end up
169      * being used. Most references to conversation-scoped objects are made via EL
170      * expressions, and in this case the performance impact is not significant
171      * relative to the overhead of EL. Note that there is one case where this
172      * proxying is not "transparent" to user code: if a proxied object passes a
173      * "this" pointer to a longer-lived object that retains that pointer then
174      * that reference can be "stale", as it points directly to an instance rather
175      * than to the proxy.
176      * <p>
177      * When the Spring aop:scoped-proxy feature is applied to conversation-scoped
178      * beans, then this functionality is disabled as aop:scoped-proxy has a very
179      * similar effect. Therefore, when this method detects that it has been invoked
180      * by a proxy object generated by aop:scoped-proxy then it returns the real
181      * object (see getRealBean) rather than another proxy. Using aop:scoped-proxy
182      * is somewhat less efficient than Orchestra's customised proxying.
183      * <p>
184      * And when the orchestra proxy needs to access the real object, it won't
185      * call this method; instead, getRealBean is called directly. See class
186      * ScopedBeanTargetSource.
187      */
188     public Object get(String name, ObjectFactory objectFactory)
189     {
190         if (log.isDebugEnabled())
191         {
192             log.debug("Method get called for bean " + name);
193         }
194 
195         if (_SpringUtils.isModifiedBeanName(name))
196         {
197             // Backwards compatibility with aop:scoped-proxy tag.
198             //
199             // The user must have included an aop:scoped-proxy within the bean definition,
200             // and here the proxy is firing to try to get the underlying bean. In this
201             // case, return a non-proxied instance of the referenced bean.
202             try
203             {
204                 String originalBeanName = _SpringUtils.getOriginalBeanName(name);
205                 String conversationName = getConversationNameForBean(name);
206                 return getRealBean(conversationName, originalBeanName, objectFactory);
207             }
208             catch(RuntimeException e)
209             {
210                 log.error("Exception while accessing bean '" + name + "'");
211                 throw e;
212             }
213         }
214         else if (!autoProxy)
215         {
216             String conversationName = getConversationNameForBean(name);
217             return getRealBean(conversationName, name, objectFactory);
218         }
219         else
220         {
221             // A call has been made by the user to the Spring getBean method
222             // (directly, or via an EL expression). Or the bean is being fetched
223             // as part of spring injection into another object.
224             //
225             // In all these cases, just return a proxy.
226             return getProxy(name, objectFactory);
227         }
228     }
229 
230     /**
231      * Return a CGLIB-generated proxy class for the beanclass that is
232      * specified by the provided beanName.
233      * <p>
234      * When any method is invoked on this proxy, it invokes method
235      * getRealBean on this same instance in order to locate a proper
236      * instance, then forwards the method call to it.
237      * <p>
238      * There is a separate proxy instance per beandef (shared across all
239      * instances of that bean). This instance is created when first needed,
240      * and cached for reuse.
241      *
242      * @since 1.1
243      */
244     protected Object getProxy(String beanName, ObjectFactory objectFactory)
245     {
246         if (log.isDebugEnabled())
247         {
248             log.debug("getProxy called for bean " + beanName);
249         }
250 
251         BeanDefinition beanDefinition = applicationContext.getBeanFactory().getBeanDefinition(beanName);
252         String conversationName = getConversationNameForBean(beanName);
253 
254         // deal with proxies required for multiple conversations.
255         // This is required to make the viewController scope work where proxies are
256         // required for each conversation a bean has been requested.
257         Map proxies = (Map) beanDefinition.getAttribute(ScopedBeanTargetSource.class.getName());
258         if (proxies == null)
259         {
260             proxies = new HashMap();
261             beanDefinition.setAttribute(ScopedBeanTargetSource.class.getName(), proxies);
262         }
263 
264         Object proxy = proxies.get(conversationName);
265         if (proxy == null)
266         {
267             if (log.isDebugEnabled())
268             {
269                 log.debug("getProxy: creating proxy for " + beanName);
270             }
271             BeanFactory beanFactory = applicationContext.getBeanFactory();
272             proxy = _SpringUtils.newProxy(this, conversationName, beanName, objectFactory, beanFactory);
273             proxies.put(conversationName, proxy);
274         }
275 
276         // Register the proxy in req scope. The first lookup of a variable using an EL expression during a
277         // request will therefore take the "long" path through JSF's VariableResolver and Spring to get here.
278         // But later lookups of this variable in the same request find the proxy directly in the request scope.
279         // The proxy could potentially be placed in the session or app scope, as there is just one instance
280         // for this spring context, and there is normally only one spring context for a webapp. However
281         // using the request scope is almost as efficient and seems safer.
282         //
283         // Note that the framework adapter might not be initialised during the Spring context initialisation
284         // phase (ie instantiation of singletons during startup), so just skip registration in those cases.
285         //
286         // Note also that when a conversation is invalidated, these objects cached in the request are NOT
287         // removed (the conversation management code is not aware that this code hidden deep in the spring
288         // adapters has done this caching). Leaving stale references in the request scope would be a very bad
289         // thing if they were real object references - which is why we do not do this caching when !autoProxy
290         // is set, or when the beandef is marked with the standard spring aop:scoped-proxy [see method
291         // get(String,ObjectFactory)]. However as these proxies always look up their target again, it is safe
292         // to leave them the request; a new bean will still be created if they are dereferenced after the target
293         // conversation is invalidated.
294         FrameworkAdapter fa = FrameworkAdapter.getCurrentInstance();
295         if (fa != null)
296         {
297             // ORCHESTRA-15 -= Leonardo Uribe =- 
298             // If it is inside a portlet using JSR-301 bridge do not add it 
299             // because there are portlet containers like liferay that 
300             // could scan request attribute map to put in xml form. In that
301             // case, FrameworkAdapter will not be found and an exception is
302             // thrown when resolving its proxy.
303             // It is possible we could have this case too with other portlet
304             // bridge implementation (myfaces 1.1 and so) but since from this
305             // point we should not call for jsf specific code, we only can
306             // check if the current request contains the key "javax.portlet.faces.phase"
307             if (fa.containsRequestAttribute(PortletOrchestraFacesContextFactory.PORTLET_LIFECYCLE_PHASE))
308             {
309                 fa.setRequestAttribute(beanName, proxy);
310             }
311         }
312 
313 
314         return proxy;
315     }
316 
317     /**
318      * Get a real bean instance (not a scoped-proxy).
319      * <p>
320      * The appropriate Conversation is retrieved; if it does not yet exist then
321      * it is created and started. The conversation name is either specified on the
322      * bean-definition via a custom attribute, or defaults to the bean name.
323      * <p>
324      * Then if the bean already exists in the Conversation it is returned. Otherwise
325      * a new instance is created, stored into the Conversation and returned.
326      * <p>
327      * When a bean is created, a proxy is actually created for it which has one or
328      * more AOP "advices" (ie method interceptors). The CurrentConversationAdvice class
329      * is always attached. Note that if the bean definition contains the aop:proxy
330      * tag (and most do) then the bean that spring creates is already a proxy, ie
331      * what is returned is a proxy of a proxy.
332      *
333      * @param conversationName
334      * @param beanName is the key within the conversation of the bean we are interested in.
335      *
336      * @since 1.1
337      */
338     protected Object getRealBean(String conversationName, String beanName, ObjectFactory objectFactory)
339     {
340         if (log.isDebugEnabled())
341         {
342             log.debug("getRealBean called for bean " + beanName);
343         }
344         ConversationManager manager = ConversationManager.getInstance();
345         Conversation conversation;
346 
347         // check if we have a conversation
348         synchronized(manager)
349         {
350             conversation = manager.getConversation(conversationName);
351             if (conversation == null)
352             {
353                 // Start the conversation. This eventually results in a
354                 // callback to the createConversation method on this class.
355                 conversation = manager.startConversation(conversationName, this);
356             }
357             else
358             {
359                 // sanity check: verify that two beans with the different scopes
360                 // do not declare the same conversationName.
361                 assertSameScope(beanName, conversation);
362             }
363         }
364 
365         // get the conversation
366         notifyAccessConversation(conversation);
367         synchronized(conversation)
368         {
369             if (!conversation.hasAttribute(beanName))
370             {
371                 Object value;
372 
373                 // Set the magic property that forces all proxies of this bean to be CGLIB proxies.
374                 // It doesn't matter if we do this multiple times..
375                 BeanDefinition beanDefinition = applicationContext.getBeanFactory().getBeanDefinition(beanName);
376                 beanDefinition.setAttribute(AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE, Boolean.TRUE);
377 
378                 try
379                 {
380                     // Create the new bean. Note that this will run the
381                     // OrchestraAdvisorBeanPostProcessor processor, which
382                     // will cause the returned object to actually be a proxy
383                     // with the CurrentConversationAdvice (at least) attached to it.
384                     value = objectFactory.getObject();
385                 }
386                 catch(org.springframework.aop.framework.AopConfigException e)
387                 {
388                     throw new IllegalStateException(
389                         "Unable to create Orchestra proxy"
390                             + " for bean " + beanName, e);
391                 }
392 
393                 conversation.setAttribute(beanName, value);
394 
395                 if (value instanceof ConversationAware)
396                 {
397                     ((ConversationAware) value).setConversation(conversation);
398                 }
399             }
400         }
401 
402         // get the bean
403         return conversation.getAttribute(beanName);
404     }
405 
406     /**
407      * Verify that the specified conversation was created by this scope object.
408      *
409      * @param beanName is just used when generating an error message on failure.
410      * @param conversation is the conversation to validate.
411      */
412     protected void assertSameScope(String beanName, Conversation conversation)
413     {
414         // Check that the conversation's factory is this one.
415         //
416         // This handles the case where two different beans declare themselves
417         // as belonging to the same named conversation but with different scope
418         // objects. Allowing that would be nasty, as the conversation
419         // properties (eg lifetime of access or manual) would depend upon which
420         // bean got created first; some other ConversationFactory would have
421         // created the conversation using its configured properties then
422         // we are now adding to that conversation a bean that really wants
423         // the conversation properties defined on this ConversationFactory.
424         //
425         // Ideally the conversation properties would be defined using
426         // the conversation name, not the scope name; this problem would
427         // then not exist. However that would lead to some fairly clumsy
428         // configuration, particularly where lots of beans without explicit
429         // conversationName attributes are used.
430 
431         if (conversation.getFactory() != this)
432         {
433             throw new IllegalArgumentException(
434                 "Inconsistent scope and conversation name detected for bean "
435                     + beanName);
436         }
437     }
438 
439     protected void notifyAccessConversation(Conversation conversation)
440     {
441     }
442 
443     /**
444      * Invoked by Spring to notify this object of the BeanFactory it is associated with.
445      * <p>
446      * This method is redundant as we also have setApplicationContext. However as this
447      * method (and the BeanFactoryAware interface on this class) were present in release
448      * 1.0 this needs to be kept for backwards compatibility.
449      */
450     public void setBeanFactory(BeanFactory beanFactory) throws BeansException
451     {
452     }
453 
454     /**
455      * Register any BeanPostProcessors that are needed by this scope.
456      * <p>
457      * This is an alternative to requiring users to also add an orchestra BeanPostProcessor element
458      * to their xml configuration file manually.
459      * <p>
460      * When a bean <i>instance</i> is created by Spring, it always runs every single BeanPostProcessor
461      * that has been registered with it.
462      *
463      * @since 1.1
464      */
465     public void defineBeanPostProcessors(ConfigurableListableBeanFactory cbf) throws BeansException
466     {
467         if (!cbf.containsSingleton(POST_PROCESSOR_BEAN_NAME))
468         {
469             BeanPostProcessor processor = new OrchestraAdvisorBeanPostProcessor(applicationContext);
470 
471             // Adding the bean to the singletons set causes it to be picked up by the standard
472             // AbstractApplicationContext.RegisterBeanPostProcessors method; that calls
473             // getBeanNamesForType(BeanPostProcessor.class, ...) which finds stuff in the
474             // singleton map even when there is no actual BeanDefinition for it.
475             //
476             // We cannot call cbf.addBeanPostProcessor even if we want to, as the singleton
477             // registration will be added again, making the processor run twice on each bean.
478             // And we need the singleton registration in order to avoid registering this once
479             // for each scope object defined in spring.
480             cbf.registerSingleton(POST_PROCESSOR_BEAN_NAME, processor);
481         }
482     }
483 
484     /**
485      * Get the conversation for the given beanName.
486      * Returns null if the conversation does not exist.
487      */
488     protected Conversation getConversationForBean(String beanDefName)
489     {
490         ConversationManager manager = ConversationManager.getInstance();
491         String conversationName = getConversationNameForBean(beanDefName);
492         Conversation conversation = manager.getConversation(conversationName);
493         return conversation;
494     }
495 
496     /**
497      * Get the conversation-name for bean instances created using the specified
498      * bean definition.
499      */
500     public String getConversationNameForBean(String beanName)
501     {
502         if (applicationContext == null)
503         {
504             throw new IllegalStateException("Null application context");
505         }
506 
507         // Look up the definition with the specified name.
508         BeanDefinition beanDefinition = applicationContext.getBeanFactory().getBeanDefinition(beanName);
509 
510         if (ScopedProxyFactoryBean.class.getName().equals(beanDefinition.getBeanClassName()))
511         {
512             // Handle unusual case.
513             //
514             // The user bean must have been defined like this:
515             //  <bean name="foo" class="example.Foo">
516             //    <....>
517             //    <aop:scopedProxy/>
518             //  </bean>
519             // In this case, Spring's ScopedProxyUtils class creates two BeanDefinition objects, one
520             // with name "foo" that creates a proxy object, and one with name "scopedTarget.foo"
521             // that actually defines the bean of type example.Foo.
522             //
523             // So what we do here is find the renamed bean definition and look there.
524             //
525             // This case does not occur when this method is invoked from within this class; the
526             // spring scope-related callbacks always deal with the beandef that is scoped to
527             // this scope - which is the original (though renamed) beandef.
528             beanName = _SpringUtils.getModifiedBeanName(beanName);
529             beanDefinition = applicationContext.getBeanFactory().getBeanDefinition(beanName); // NON-NLS
530         }
531 
532         String convName = getExplicitConversationName(beanDefinition);
533         if (convName == null)
534         {
535             // The beanname might have been of form "scopedTarget.foo" (esp from registerDestructionCallback).
536             // But in this case, the conversation name will just be "foo", so strip the prefix off.
537             //
538             // Note that this does happen quite often for calls from within this class when aop:scoped-proxy
539             // is being used (which is not recommended but is supported).
540             convName = _SpringUtils.getOriginalBeanName(beanName);
541         }
542         return convName;
543     }
544 
545     /**
546      * Return the explicit conversation name for this bean definition, or null if there is none.
547      * <p>
548      * This is a separate method so that subclasses can determine conversation names via alternate methods.
549      * In particular, a subclass may want to look for an annotation on the class specified by the definition.
550      *
551      * @since 1.1
552      */
553     protected String getExplicitConversationName(BeanDefinition beanDef)
554     {
555         String attr = (String) beanDef.getAttribute(
556                 BeanDefinitionConversationNameAttrDecorator.CONVERSATION_NAME_ATTRIBUTE);
557         return attr;
558     }
559 
560     /**
561      * Strip off any Spring namespace (eg scopedTarget).
562      * <p>
563      * This method will simply strip off anything before the first dot.
564      *
565      * @deprecated Should not be necessary in user code.
566      */
567     protected String buildBeanName(String name)
568     {
569         if (name == null)
570         {
571             return null;
572         }
573 
574         int pos = name.indexOf('.');
575         if (pos < 0)
576         {
577             return name;
578         }
579 
580         return name.substring(pos + 1);
581     }
582 
583     public Object remove(String name)
584     {
585         throw new UnsupportedOperationException();
586     }
587 
588     /**
589      * Add the given runnable wrapped within an
590      * {@link org.apache.myfaces.orchestra.conversation.ConversationBindingListener} to
591      * the conversation map.
592      * <p>
593      * This ensures it will be called during conversation destroy.
594      * <p>
595      * Spring calls this method whenever a bean in this scope is created, if that bean
596      * has a "destroy method". Note however that it appears that it can also call it even
597      * for beans that do not have a destroy method when there is a "destruction aware"
598      * BeanPostProcessor attached to the context (spring version 2.5 at least).
599      * <p>
600      * When an aop:scoped-proxy has been used inside the bean, then the "new" definition
601      * does not have any scope attribute, so orchestra is not invoked for it. However
602      * the "renamed" bean does, and so this is called.
603      */
604     public void registerDestructionCallback(String name, final Runnable runnable)
605     {
606         if (log.isDebugEnabled())
607         {
608             log.debug("registerDestructionCallback for [" + name + "]");
609         }
610 
611         Conversation conversation = getConversationForBean(name);
612         if (conversation == null)
613         {
614             // This should never happen because this should only be called after the bean
615             // instance has been created via scope.getBean, which always creates the
616             // conversation for the bean.
617             throw new IllegalStateException("No conversation for bean [" + name + "]");
618         }
619         if (runnable == null)
620         {
621             throw new IllegalStateException("No runnable object for bean [" + name + "]");
622         }
623 
624         // Add an object to the conversation as a bean so that when the conversation is removed
625         // its valueUnbound method will be called. However we never need to retrieve this object
626         // from the context by name, so use a totally unique name as the bean key.
627         conversation.setAttribute(
628             runnable.getClass().getName() + "@" + System.identityHashCode(runnable),
629             new ConversationBindingListener()
630             {
631                 public void valueBound(ConversationBindingEvent event)
632                 {
633                 }
634 
635                 public void valueUnbound(ConversationBindingEvent event)
636                 {
637                     runnable.run();
638                 }
639             }
640         );
641     }
642 
643     /**
644      * Get an ApplicationContext injected by Spring. See ApplicationContextAware interface.
645      */
646     public void setApplicationContext(ApplicationContext applicationContext) throws BeansException
647     {
648         if (!(applicationContext instanceof ConfigurableApplicationContext))
649         {
650             throw new IllegalArgumentException("a ConfigurableApplicationContext is required");
651         }
652 
653         this.applicationContext = (ConfigurableApplicationContext) applicationContext;
654         defineBeanPostProcessors(this.applicationContext.getBeanFactory());
655     }
656 
657     /**
658      * @since 1.2
659      */
660     protected ConfigurableApplicationContext getApplicationContext()
661     {
662         return applicationContext;
663     }
664 
665     /**
666      * Return the Advisors that should be applied to beans associated with this scope object.
667      * <p>
668      * Note that logically Advisors are associated with a Conversation. It is an implementation
669      * artifact of the Spring implementation of Orchestra that we use a spring Scope object to
670      * hold the advices; theoretically with other dependency-injection frameworks we could
671      * configure things differently. 
672      */
673     Advisor[] getAdvisors(Conversation conversation, String beanName)
674     {
675         Advice[] advices = this.getAdvices();
676         if ((advices == null) || (advices.length == 0))
677         {
678             advices = NO_ADVICES;
679         }
680 
681         // wrap every Advice in an Advisor instance that returns it in all cases
682         int len = advices.length + 1;
683         Advisor[] advisors = new Advisor[len];
684 
685         // always add the standard CurrentConversationAdvice, and do it FIRST, so it runs first
686         Advice currConvAdvice = new CurrentConversationAdvice(conversation, beanName);
687         advisors[0] = new SimpleAdvisor(currConvAdvice);
688         for(int i=0; i<advices.length; ++i) 
689         {
690             advisors[i+1] = new SimpleAdvisor(advices[i]);
691         }
692 
693         return advisors;
694     }
695 
696     /**
697      * Return a proxy object that "enters" the specified conversation before forwarding the
698      * method call on to the specified instance.
699      * <p>
700      * Entering the conversation means running all the Advices associated with the conversation.
701      * The specified conversation object is assumed to use this Scope object.
702      */
703     Object createProxyFor(Conversation conversation, Object instance)
704     {
705         if (instance instanceof SpringProxy)
706         {
707             // This is already a proxy, so don't wrap it again. Doing this check means that
708             // user code can safely write things like
709             //    return ConversationUtils.bindToCurrent(this)
710             // without worrying about whether "this" is a spring bean marked as conversation-scoped
711             // or not. Requiring beans to know about the configuration setup is bad practice.
712             //
713             // Ideally we would check here that this instance is indeed a proxy for the
714             // specified conversation and throw an exception. However that is just a
715             // nice-to-have.
716             return instance;
717         }
718         
719         // The currentConversationAdvice constructor requires a beanName parameter. As the
720         // instance we are wrapping here is usually not defined in the dependency-injection
721         // framework configuration at all, we have to invent a dummy name here.
722         //
723         // The beanName affects ConversationUtils methods getCurrentBean and invalidateAndRestartCurrent.
724         // Neither should ever be called by beans artificially wrapped in a proxy like this, so any old
725         // "bean name" will do. Including the class-name of the bean we wrap seems helpful here..
726         String beanName = "dummy$" + instance.getClass().getName();
727 
728         ProxyFactory proxyFactory = new ProxyFactory(instance);
729         proxyFactory.setProxyTargetClass(true);
730         Advisor[] advisors = getAdvisors(conversation, beanName);
731         for(int i=0; i<advisors.length; ++i)
732         {
733             proxyFactory.addAdvisor(advisors[i]);
734         }
735 
736         proxyFactory.addInterface(SpringProxy.class);
737         return proxyFactory.getProxy(instance.getClass().getClassLoader());
738     }
739 }