org.traffic.database.Database.java Source code

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Here is the source code for org.traffic.database.Database.java

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/*
 * Copyright (c) 2011, Daniel Kuenne
 * 
 * This file is part of TrafficJamDroid.
 *
 * TrafficJamDroid is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * TrafficJamDroid 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with TrafficJamDroid.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.traffic.database;

import java.io.File;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;

/**
 * This class provides a bunch of methods to interact with the database. It sets
 * up the connection with a given configuration and allows the administration of
 * {@link Session} and {@link org.hibernate.Transaction}.
 * 
 * @author Daniel Kuenne
 * @version $LastChangedRevision: 220 $
 * @see SessionFactory
 * @see Session
 * @see org.hibernate.Transaction
 * @see Configuration
 */
public class Database {

    /** The factory to create new sessions */
    private static SessionFactory sessionFactory = null;

    /** The active configuration */
    private static Configuration hibernate_config;

    /**
     * Initializes the database-connection, loads the configuration-files and
     * creates the session-factory.
     * 
     * @throws IllegalStateException
     *             The database is already initialized
     */
    public static void initialize() throws IllegalStateException {
        if (isInitialized())
            throw new IllegalStateException("Database was already initialized");

        File config_file = new File("res/hibernate.cfg.xml");
        sessionFactory = buildSessionFactory(config_file);
    }

    /**
     * Checks whether the connection is initialized or not.
     * 
     * @return The status of the initialization
     */
    public static boolean isInitialized() {
        return hibernate_config != null;
    }

    /**
     * Resets the connection to the default-values.
     */
    public static void reset() {
        if (hibernate_config == null)
            throw new ExceptionInInitializerError("No config present, cant reset!");

        SchemaExport ex = new SchemaExport(hibernate_config);
        ex.create(false, true);
    }

    /**
     * Creates the session-factory with the given configuration.
     * 
     * @param config_file
     *            The file containing the configuration
     * @return The {@link SessionFactory}
     */
    protected static SessionFactory buildSessionFactory(File config_file) {
        try {
            hibernate_config = new Configuration().configure(config_file);
            return hibernate_config.buildSessionFactory();
        } catch (Throwable ex) {
            System.err.println("Initial SessionFactory creation failed. " + ex);
            throw new ExceptionInInitializerError(ex);
        }
    }

    /**
     * Returns the current session-factory.
     * 
     * @return The {@link SessionFactory}
     */
    private static SessionFactory getSessionFactory() {
        if (!isInitialized())
            initialize();

        return sessionFactory;
    }

    /**
     * Returns the current Session.
     * 
     * @return The {@link Session}
     */
    public static Session session() {
        return getSessionFactory().getCurrentSession();
    }

    /**
     * Starts a new {@link org.hibernate.Transaction} within the current
     * {@link Session}.
     */
    public static void begin() {
        getSessionFactory().getCurrentSession().beginTransaction();
    }

    /**
     * Ends an open {@link org.hibernate.Transaction}.
     * 
     * @param commit
     *            Flag to perform a commit or a rollback
     */
    public static void end(boolean commit) {
        if (commit)
            commit();
        else
            rollback();
    }

    /**
     * Revokes all changes and performs a rollback on the
     * {@link org.hibernate.Transaction}.
     */
    public static void rollback() {
        getSessionFactory().getCurrentSession().getTransaction().rollback();
    }

    /**
     * Performs a commit on the {@link org.hibernate.Transaction}.
     */
    public static void commit() {
        getSessionFactory().getCurrentSession().getTransaction().commit();
    }

    /**
     * Opens a new {@link Session}.
     * 
     * @return The new {@link Session}
     */
    public static Session openNewSession() {
        return getSessionFactory().openSession();
    }
}