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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 org.apache.commons.logging.Log;
23  import org.apache.commons.logging.LogFactory;
24  import org.apache.myfaces.orchestra.conversation.Conversation;
25  import org.springframework.aop.Advisor;
26  import org.springframework.aop.TargetSource;
27  import org.springframework.aop.framework.autoproxy.AbstractAutoProxyCreator;
28  import org.springframework.beans.BeansException;
29  import org.springframework.beans.factory.NoSuchBeanDefinitionException;
30  import org.springframework.beans.factory.config.BeanDefinition;
31  import org.springframework.context.ConfigurableApplicationContext;
32  
33  /**
34   * Define a BeanPostProcessor that is run when any bean is created by Spring.
35   * <p>
36   * This checks whether the scope of the bean is an Orchestra scope. If not, it has
37   * no effect.
38   * <p>
39   * For orchestra-scoped beans, this ensures that a CGLIB-generated proxy object is
40   * returned that wraps the real bean requested (ie holds an internal reference to
41   * an instance of the real bean). The proxy has the CurrentConversationAdvice
42   * attached to it always, plus any other advices that are configured for the scope
43   * that the bean is associated with.
44   * <p>
45   * These advices then run on each invocation of any method on the proxy.
46   * <p>
47   * Note that the proxy may have other advices attached to it to, as specified by
48   * any other BeanPostProcessor objects that happen to be registered and relevant
49   * to the created bean (eg an advice to handle declarative transactions).
50   */
51  class OrchestraAdvisorBeanPostProcessor extends AbstractAutoProxyCreator
52  {
53      private static final long serialVersionUID = 1;
54      private final Log log = LogFactory.getLog(OrchestraAdvisorBeanPostProcessor.class);
55      private ConfigurableApplicationContext appContext;
56  
57  
58      public OrchestraAdvisorBeanPostProcessor(ConfigurableApplicationContext appContext)
59      {
60          this.appContext = appContext;
61  
62          // Always force CGLIB to be used to generate proxies, rather than java.lang.reflect.Proxy.
63          //
64          // Without this, the Orchestra scoped-proxy instance will not work; it requires
65          // the target to fully implement the same class it is proxying, not just the
66          // interfaces on the target class.
67          //
68          //
69          // Alas, this is not sufficient to solve all the problems. If a BeanPostProcessor runs
70          // before this processor, and it creates a CGLIB based proxy, then this class creates
71          // a new proxy that *replaces* that one by peeking into the preceding proxy to find
72          // its real target class/interfaces and its advices and merging that data with the
73          // settings here (see method Cglib2AopProxy.getProxy for details). However if an
74          // earlier BeanPostProcessor has created a java.lang.reflect.Proxy proxy instance
75          // then this merging does not occur; instead this class just tries to wrap that proxy
76          // in another cglib proxy, but that fails because java.lang.reflect.Proxy creates
77          // final (unsubclassable) classes. So in short either this BeanPostProcessor needs to
78          // be the *first* processor, or some trick is needed to force all BeanPostProcessors
79          // to use cglib. This can be done by setting a special attribute in the BeanDefinition
80          // for a bean, and AbstractSpringOrchestraScope does this.
81          //
82          // Note that forging cglib to be used for proxies is also necessary when creating a
83          // "scoped proxy" for an object. The aop:scoped-proxy class also has the same needs
84          // as the Orchestra scoped-proxy, and also forces CGLIB usage, using the same method
85          // (setting AutoProxyUtils.PRESERVE_TARGET_CLASS_ATTRIBUTE in the attributes of the
86          // BeanDefinition of the target bean).
87          setProxyTargetClass(true);
88      }
89  
90      protected Object[] getAdvicesAndAdvisorsForBean(Class beanClass, String beanName,
91              TargetSource customTargetSource) throws BeansException
92      {
93          BeanDefinition bd;
94          try 
95          {
96              bd = appContext.getBeanFactory().getBeanDefinition(beanName);
97          }
98          catch(NoSuchBeanDefinitionException e)
99          {
100             // odd. However it appears that there are some "special" beans that Spring
101             // creates that cause the BeanPostProcessor to be run even though they do
102             // not have a corresponding definition. The name "(inner bean)" is one of them,
103             // but there are also names of form "example.classname#xyz123" passed to here.
104             if (log.isDebugEnabled())
105             {
106                 log.debug("Bean has no definition:" + beanName);
107             }
108             return null;
109         }
110 
111         String scopeName = bd.getScope();
112         if (scopeName == null)
113         {
114             // does this ever happen?
115             if (log.isDebugEnabled())
116             {
117                 log.debug("no scope associated with bean " + beanName);
118             }
119             return null;
120         }
121 
122         if (log.isDebugEnabled())
123         {
124             log.debug("Processing scope [" + scopeName + "]");
125         }
126 
127         Object scopeObj = appContext.getBeanFactory().getRegisteredScope(scopeName);
128         if (scopeObj == null)
129         {
130             // Ok, this is not an orchestra-scoped bean. This happens for standard scopes
131             // like Singleton.
132             if (log.isDebugEnabled())
133             {
134                 log.debug("No scope object for scope [" + scopeName + "]");
135             }
136             return null;
137         }
138         else if (scopeObj instanceof AbstractSpringOrchestraScope == false)
139         {
140             // ok, this is not an orchestra-scoped bean
141             if (log.isDebugEnabled())
142             {
143                 log.debug(
144                     "scope associated with bean " + beanName +
145                     " is not orchestra:" + scopeObj.getClass().getName());
146             }
147             return null;
148         }
149 
150         AbstractSpringOrchestraScope scopeForThisBean = (AbstractSpringOrchestraScope) scopeObj;
151         Conversation conversation = scopeForThisBean.getConversationForBean(beanName);
152             
153         if (conversation == null)
154         {
155             // In general, getConversationForBean is allowed to return null. However in this case
156             // that is really not expected. Calling getBean for a bean in a scope only ever calls
157             // the get method on the scope object. The only way an instance can *really* be
158             // created is by invoking the ObjectFactory that is passed to the scope object. And
159             // the AbstractSpringOrchestraScope type only ever does that after ensuring that the
160             // conversation object has been created.
161             //
162             // Therefore, this is theoretically impossible..
163             throw new IllegalStateException("Internal error: null conversation for bean " + beanName);
164         }
165 
166         Advisor[] advisors = scopeForThisBean.getAdvisors(conversation, beanName);
167         return advisors;
168     }
169 }