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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  package org.apache.myfaces.orchestra.conversation.spring;
20  
21  import org.springframework.orm.jpa.EntityManagerHolder;
22  import org.springframework.transaction.support.TransactionSynchronizationManager;
23  
24  import javax.persistence.EntityManager;
25  import javax.persistence.EntityManagerFactory;
26  import javax.persistence.FlushModeType;
27  import java.util.Stack;
28  
29  /***
30   * A factory for PersistenceContext objects which integrates with Spring's JPA
31   * support.
32   * <p>
33   * When a bean is invoked which is associated with a conversation, but the conversation
34   * does not yet have a PersistenceContext, then this factory is used to create a
35   * PersistenceContext.
36   * <p>
37   * The returned object knows how to configure itself as the "current persistence context"
38   * within Spring when a method on that bean is invoked, and how to restore the earlier
39   * "current persistence context" after the method returns.
40   */
41  public class JpaPersistenceContextFactory implements PersistenceContextFactory
42  {
43  	private EntityManagerFactory entityManagerFactory;
44  
45  	public PersistenceContext create()
46  	{
47  		final EntityManager em = entityManagerFactory.createEntityManager();
48  		em.setFlushMode(FlushModeType.COMMIT);
49  
50  		return new PersistenceContext()
51  		{
52  			private final Stack bindings = new Stack();
53  
54  			// Store the current EntityManagerHolder on a stack, then install our own as the
55  			// current EntityManagerHolder. Storing the old one allows us to restore it when
56  			// this context is "unbound".
57  			//
58  			// Orchestra calls bind every time a method is invoked on a bean which has
59  			// a conversation with a persistence context. The unbind is invoked when the
60  			// invoked method on that bean returns.
61  			//
62  			// When a bean has a property that has been annotated as @PersistenceContext,
63  			// Spring injects a proxy that looks up the "current" persistence context whenever
64  			// a method is invoked on it. Because Orchestra has called persistencecontext.bind
65  			// when the bean was first entered, and this object's bind method has installed
66  			// itself as the "current" spring persistence context object, the bean sees the
67  			// persistence context that is associated with its conversation.
68  			//
69  			// TODO: what happens when a bean invokes a method on itself? Does bind get called
70  			// again? If so, then this implementation is inefficient as it will push itself
71  			// onto the stack over and over again. This could be optimised by checking whether
72  			// this is the current context, and if so just incrementing a counter rather than
73  			// pushing onto a stack...
74  			public void bind()
75  			{
76  				synchronized(bindings)
77  				{
78  					EntityManagerHolder current = (EntityManagerHolder)
79  						TransactionSynchronizationManager.getResource(entityManagerFactory);
80  
81  					if (current != null)
82  					{
83  						TransactionSynchronizationManager.unbindResource(entityManagerFactory);
84  					}
85  
86  					bindings.push(current);
87  
88  					TransactionSynchronizationManager.bindResource(entityManagerFactory,
89  						new EntityManagerHolder(em));
90  				}
91  			}
92  
93  			public void unbind()
94  			{
95  				synchronized(bindings)
96  				{
97  					if (TransactionSynchronizationManager.hasResource(entityManagerFactory))
98  					{
99  						TransactionSynchronizationManager.unbindResource(entityManagerFactory);
100 					}
101 
102 					Object holder = null;
103 					if (bindings.size() > 0)
104 					{
105 						holder = bindings.pop();
106 					}
107 					if (holder != null)
108 					{
109 						TransactionSynchronizationManager.bindResource(entityManagerFactory,
110 							holder);
111 					}
112 				}
113 			}
114 
115 			public void close()
116 			{
117 				em.close();
118 			}
119 		};
120 	}
121 
122 	public EntityManagerFactory getEntityManagerFactory()
123 	{
124 		return entityManagerFactory;
125 	}
126 
127 	public void setEntityManagerFactory(EntityManagerFactory entityManagerFactory)
128 	{
129 		this.entityManagerFactory = entityManagerFactory;
130 	}
131 }