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      1 /**
      2  * Copyright (C) 2010 Google, Inc.
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.inject.persist.jpa;
     18 
     19 import com.google.common.annotations.VisibleForTesting;
     20 import com.google.common.base.Preconditions;
     21 import com.google.inject.Inject;
     22 import com.google.inject.Provider;
     23 import com.google.inject.Singleton;
     24 import com.google.inject.persist.PersistService;
     25 import com.google.inject.persist.UnitOfWork;
     26 
     27 import java.lang.annotation.Documented;
     28 import java.lang.annotation.ElementType;
     29 import java.lang.annotation.Retention;
     30 import java.lang.annotation.RetentionPolicy;
     31 import java.lang.annotation.Target;
     32 import java.util.Map;
     33 
     34 import javax.persistence.EntityManager;
     35 import javax.persistence.EntityManagerFactory;
     36 import javax.persistence.Persistence;
     37 
     38 /**
     39  * @author Dhanji R. Prasanna (dhanji (at) gmail.com)
     40  */
     41 @Singleton
     42 class JpaPersistService implements Provider<EntityManager>, UnitOfWork, PersistService {
     43   private final ThreadLocal<EntityManager> entityManager = new ThreadLocal<EntityManager>();
     44 
     45   private final String persistenceUnitName;
     46   private final Map<?,?> persistenceProperties;
     47 
     48   @Inject
     49   public JpaPersistService(@Jpa String persistenceUnitName,
     50       @Nullable @Jpa Map<?,?> persistenceProperties) {
     51     this.persistenceUnitName = persistenceUnitName;
     52     this.persistenceProperties = persistenceProperties;
     53   }
     54 
     55   public EntityManager get() {
     56     if (!isWorking()) {
     57       begin();
     58     }
     59 
     60     EntityManager em = entityManager.get();
     61     Preconditions.checkState(null != em, "Requested EntityManager outside work unit. "
     62         + "Try calling UnitOfWork.begin() first, or use a PersistFilter if you "
     63         + "are inside a servlet environment.");
     64 
     65     return em;
     66   }
     67 
     68   public boolean isWorking() {
     69     return entityManager.get() != null;
     70   }
     71 
     72   public void begin() {
     73     Preconditions.checkState(null == entityManager.get(),
     74         "Work already begun on this thread. Looks like you have called UnitOfWork.begin() twice"
     75          + " without a balancing call to end() in between.");
     76 
     77     entityManager.set(emFactory.createEntityManager());
     78   }
     79 
     80   public void end() {
     81     EntityManager em = entityManager.get();
     82 
     83     // Let's not penalize users for calling end() multiple times.
     84     if (null == em) {
     85       return;
     86     }
     87 
     88     try {
     89       em.close();
     90     }
     91     finally {
     92       entityManager.remove();
     93     }
     94   }
     95 
     96   private volatile EntityManagerFactory emFactory;
     97 
     98   @VisibleForTesting
     99   synchronized void start(EntityManagerFactory emFactory) {
    100     this.emFactory = emFactory;
    101   }
    102 
    103   public synchronized void start() {
    104     Preconditions.checkState(null == emFactory, "Persistence service was already initialized.");
    105 
    106     if (null != persistenceProperties) {
    107       this.emFactory = Persistence
    108           .createEntityManagerFactory(persistenceUnitName, persistenceProperties);
    109     } else {
    110       this.emFactory = Persistence.createEntityManagerFactory(persistenceUnitName);
    111     }
    112   }
    113 
    114   public synchronized void stop() {
    115     Preconditions.checkState(emFactory.isOpen(), "Persistence service was already shut down.");
    116     emFactory.close();
    117   }
    118 
    119   @Singleton
    120   public static class EntityManagerFactoryProvider implements Provider<EntityManagerFactory> {
    121     private final JpaPersistService emProvider;
    122 
    123     @Inject
    124     public EntityManagerFactoryProvider(JpaPersistService emProvider) {
    125       this.emProvider = emProvider;
    126     }
    127 
    128     public EntityManagerFactory get() {
    129       assert null != emProvider.emFactory;
    130       return emProvider.emFactory;
    131     }
    132   }
    133 
    134   @Documented
    135   @Retention(RetentionPolicy.RUNTIME)
    136   @Target(ElementType.PARAMETER)
    137   private @interface Nullable { }
    138 
    139 }
    140