eu.lp0.cursus.db.DatabaseSession.java Source code

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Here is the source code for eu.lp0.cursus.db.DatabaseSession.java

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/*
   cursus - Race series management program
   Copyright 2011, 2013-2014  Simon Arlott
    
   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU Affero General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
    
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU Affero General Public License for more details.
    
   You should have received a copy of the GNU Affero General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package eu.lp0.cursus.db;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.EntityTransaction;

import com.google.common.base.Preconditions;

public class DatabaseSession {
    private static final ThreadLocal<EntityManager> THREADS = new ThreadLocal<EntityManager>();
    private final EntityManagerFactory emf;
    private long openCount;

    DatabaseSession(EntityManagerFactory emf) {
        this.emf = emf;
    }

    void startSession() {
        Preconditions.checkState(THREADS.get() == null, "Session already open"); //$NON-NLS-1$
        synchronized (this) {
            Preconditions.checkState(emf.isOpen(), "Factory not open"); //$NON-NLS-1$
            openCount++;
        }
        THREADS.set(emf.createEntityManager());
    }

    public static EntityManager getEntityManager() {
        EntityManager em = THREADS.get();
        Preconditions.checkState(em != null, "Session not open"); //$NON-NLS-1$
        return em;
    }

    public static EntityTransaction getTransaction() {
        return getEntityManager().getTransaction();
    }

    public static void begin() {
        getTransaction().begin();
    }

    public static void commit() {
        getTransaction().commit();
    }

    public static void rollback() {
        getTransaction().rollback();
    }

    void endSession() {
        getEntityManager().close();
        synchronized (this) {
            openCount--;
        }
        THREADS.set(null);
    }

    boolean isFactoryActive() {
        synchronized (this) {
            return openCount > 0;
        }
    }

    boolean closeFactory(boolean force) {
        if (!emf.isOpen()) {
            return true;
        }

        synchronized (this) {
            if (openCount == 0 || force) {
                shutdown();
                return true;
            }
        }
        return false;
    }

    private void shutdown() {
        EntityManager em = emf.createEntityManager();
        try {
            em.getTransaction().begin();
            em.createNativeQuery("SHUTDOWN").executeUpdate(); //$NON-NLS-1$
        } finally {
            em.close();
        }

        emf.close();
    }

    @Override
    protected void finalize() throws Throwable {
        super.finalize();
        if (emf.isOpen()) {
            shutdown();
        }
    }
}