eu.ist_phosphorus.harmony.idb.database.TransactionManager.java Source code

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Here is the source code for eu.ist_phosphorus.harmony.idb.database.TransactionManager.java

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/**
*  This code is part of the Harmony System implemented in Work Package 1 
*  of the Phosphorus project. This work is supported by the European 
*  Comission under the Sixth Framework Programme with contract number 
*  IST-034115.
*
*  Copyright (C) 2006-2009 Phosphorus WP1 partners. Phosphorus Consortium.
*  http://ist-phosphorus.eu/
 *
 * This is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation; either version 2.1 of
 * the License, or (at your option) any later version.
 *
 * This software 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this software; if not, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
 */

package eu.ist_phosphorus.harmony.idb.database;

import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;

import eu.ist_phosphorus.harmony.idb.exceptions.database.DatabaseException;

/**
 * This class takes care of accessing the database in a nice and tidy
 * way. It opens a session, opens a transaction in this session,
 * executes a database operation, commits the transaction, and closes
 * the session. If anything goes wrong, the transaction is rolled back
 * and a DatabaseException is thrown.
 *
 * The actual database operation is not part of this class, but is an
 * abstract method dbOperation() that has to be defined in a child class.
 *
 * @author Christian de Waal
 *
 */
public abstract class TransactionManager {
    /** This session object can be used from within the dbOperation() method to access the database. */
    protected Session session = null;
    /** Any object that can be handed to the TransactionManager through the appropriate constructor. */
    protected Object arg = null;
    /** Any kind of result of the database operation that can be retrieved using the getResult() method. */
    protected Object result = null;

    public Set<Object> refreshObjects;

    /** Default constructor. */
    public TransactionManager() throws DatabaseException {
        start();
    }

    /** Constructor with some additional argument. */
    public TransactionManager(Object arg) throws DatabaseException {
        this.arg = arg;
        start();
    }

    /** Constructor with some additional argument. */
    public TransactionManager(HashSet<Object> arg) throws DatabaseException {
        this.refreshObjects = arg;
        start();
    }

    /** Constructor with some additional argument. */
    public TransactionManager(Object arg1, HashSet<Object> arg2) throws DatabaseException {
        this.arg = arg1;
        this.refreshObjects = arg2;
        start();
    }

    /** Retrieve result of a database operation. */
    public Object getResult() {
        return this.result;
    }

    /** Execute the database operation, take care of cleaning up in case of errors. */
    private void start() throws DatabaseException {
        this.session = DbConnectionManager.getCurrentSession();

        final Transaction trans = this.session.beginTransaction();
        DatabaseException exception = null;
        try {
            this.dbOperation();
            this.session.flush();
            trans.commit();
            //            this.session.close();
        } catch (final Exception ex) {
            exception = new DatabaseException(ex.getMessage(), ex);
        }

        if (exception != null) {
            trans.rollback();
            DbConnectionManager.closeSession();
            throw exception;
        }

        // if transaction was successfull, refres dependent object in session
        refreshObjects(this.session);
    }

    private void refreshObjects(Session sess) {
        if (refreshObjects != null) {
            for (Object o : refreshObjects) {
                sess.refresh(o);
            }
        }
    }

    /** The actual database operation to be defined in a child class. */
    protected abstract void dbOperation() throws Exception;
}