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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 }