name.marcelomorales.siqisiqi.openjpa.guice.EntityManagerProvider.java Source code

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Here is the source code for name.marcelomorales.siqisiqi.openjpa.guice.EntityManagerProvider.java

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/*
 * Copyright 2013 Marcelo Morales me@marcelomorales.name
 *
 *    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.
 */

package name.marcelomorales.siqisiqi.openjpa.guice;

import com.google.common.base.Preconditions;

import javax.inject.Inject;
import javax.inject.Provider;
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;

/**
 * @author Marcelo Morales
 *         Since: 9/17/13
 */
public class EntityManagerProvider implements Provider<EntityManager>, UnitOfWork {

    private final ThreadLocal<EntityManager> entityManager = new ThreadLocal<>();

    private final EntityManagerFactory emFactory;

    @Inject
    public EntityManagerProvider(EntityManagerFactory emFactory) {
        this.emFactory = emFactory;
    }

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

        EntityManager em = entityManager.get();
        Preconditions.checkState(null != em, "Requested EntityManager outside work unit.");

        return em;
    }

    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());
    }

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

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

        em.close();
        entityManager.remove();
    }

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

}