com.github.zhengframework.jpa.JpaService Maven / Gradle / Ivy

Go to download
package com.github.zhengframework.jpa;

/*-
 * #%L
 * zheng-jpa
 * %%
 * Copyright (C) 2020 Zheng MingHai
 * %%
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * #L%
 */

import com.google.common.base.Preconditions;
import com.google.inject.persist.PersistService;
import com.google.inject.persist.UnitOfWork;
import java.util.Iterator;
import java.util.ServiceLoader;
import javax.inject.Inject;
import javax.inject.Provider;
import javax.inject.Singleton;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.spi.PersistenceUnitInfo;

@Singleton
public class JpaService implements Provider, UnitOfWork, PersistService {

  private final ThreadLocal entityManager = new ThreadLocal<>();
  private final PersistenceUnitInfo persistenceUnitInfo;
  private volatile EntityManagerFactory emFactory;

  @Inject
  public JpaService(PersistenceUnitInfo persistenceUnitInfo) {
    this.persistenceUnitInfo = persistenceUnitInfo;
  }

  @Override
  public EntityManager get() {
    if (!isWorking()) {
      begin();
    }

    EntityManager em = entityManager.get();
    Preconditions.checkState(
        null != em,
        "Requested EntityManager outside work unit. "
            + "Try calling UnitOfWork.begin() first, or use a PersistFilter if you "
            + "are inside a servlet environment.");

    return em;
  }

  public boolean isWorking() {
    return entityManager.get() != null;
  }

  @Override
  public void begin() {
    Preconditions.checkState(
        null == entityManager.get(),
        "Work already begun on this thread. Looks like you have called UnitOfWork.begin() twice"
            + " without a balancing call to end() in between.");

    entityManager.set(emFactory.createEntityManager());
  }

  @Override
  public void end() {
    EntityManager em = entityManager.get();

    // Let's not penalize users for calling end() multiple times.
    if (null == em) {
      return;
    }

    try {
      em.close();
    } finally {
      entityManager.remove();
    }
  }

  @Override
  public synchronized void start() {
    Preconditions.checkState(null == emFactory, "Persistence service was already initialized.");
    ServiceLoader load =
        ServiceLoader.load(EntityManagerFactoryProvider.class);
    Iterator iterator = load.iterator();
    if (iterator.hasNext()) {
      EntityManagerFactoryProvider entityManagerFactoryProvider = iterator.next();
      emFactory = entityManagerFactoryProvider.get(persistenceUnitInfo);
    } else {
      throw new IllegalArgumentException("request EntityManagerFactoryProvider Implements");
    }
  }

  @Override
  public synchronized void stop() {
    if (emFactory.isOpen()) {
      emFactory.close();
    }
  }

  @Singleton
  public static class EntityManagerFactoryInternalProvider
      implements Provider {

    private final JpaService emProvider;

    @Inject
    public EntityManagerFactoryInternalProvider(JpaService emProvider) {
      this.emProvider = emProvider;
    }

    @Override
    public EntityManagerFactory get() {
      assert null != emProvider.emFactory;
      return emProvider.emFactory;
    }
  }
}