AbstractFactory.java

/**
 * OpenSpotLight - Open Source IT Governance Platform
 *
 * Copyright (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA
 * or third-party contributors as indicated by the @author tags or express
 * copyright attribution statements applied by the authors.  All third-party
 * contributions are distributed under license by CARAVELATECH CONSULTORIA E
 * TECNOLOGIA EM INFORMATICA LTDA.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * 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 Lesser General Public License  for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 *
 ***********************************************************************
 * OpenSpotLight - Plataforma de Governança de TI de Código Aberto
 *
 * Direitos Autorais Reservados (c) 2009, CARAVELATECH CONSULTORIA E TECNOLOGIA
 * EM INFORMATICA LTDA ou como contribuidores terceiros indicados pela etiqueta
 * @author ou por expressa atribuição de direito autoral declarada e atribuída pelo autor.
 * Todas as contribuições de terceiros estão distribuídas sob licença da
 * CARAVELATECH CONSULTORIA E TECNOLOGIA EM INFORMATICA LTDA.
 *
 * Este programa é software livre; você pode redistribuí-lo e/ou modificá-lo sob os
 * termos da Licença Pública Geral Menor do GNU conforme publicada pela Free Software
 * Foundation.
 *
 * Este programa é distribuído na expectativa de que seja útil, porém, SEM NENHUMA
 * GARANTIA; nem mesmo a garantia implícita de COMERCIABILIDADE OU ADEQUAÇÃO A UMA
 * FINALIDADE ESPECÍFICA. Consulte a Licença Pública Geral Menor do GNU para mais detalhes.
 *
 * Você deve ter recebido uma cópia da Licença Pública Geral Menor do GNU junto com este
 * programa; se não, escreva para:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */

package org.openspotlight.common.util;

import java.io.IOException;
import java.io.InputStream;
import java.util.HashMap;
import java.util.Map;
import java.util.Properties;

import org.openspotlight.common.exception.AbstractFactoryException;

/**
 * A factory for creating Abstract objects.
 */
public abstract class AbstractFactory {

    /** The factory map. */
    private static Map<Class<? extends AbstractFactory>, AbstractFactory> factoryMap =
                                                                                         new HashMap<Class<? extends AbstractFactory>, AbstractFactory>();

    /**
     * Load props.
     * 
     * @param clazz the clazz
     * @return the properties
     * @throws AbstractFactoryException the abstract factory exception
     */
    private static Properties loadProps(final Class<?> clazz)
        throws AbstractFactoryException {
        final String resource = clazz.getName().replace('.', '/').concat(".properties");
        try {
            final InputStream inputStream = AbstractFactory.class.getClassLoader().getResourceAsStream(resource);
            final Properties props = new Properties();
            props.load(inputStream);
            return props;
        } catch (final IOException e) {
            throw new AbstractFactoryException("Error on attempt to load factory properties file " + resource, e);
        }
    }

    /**
     * Gets the default instance.
     * 
     * @param clazz the clazz
     * @return the default instance
     * @throws AbstractFactoryException the abstract factory exception
     */
    @SuppressWarnings("unchecked")
    public static <T extends AbstractFactory> T getDefaultInstance(final Class<T> clazz)
        throws AbstractFactoryException {
        T factory = null;
        try {
            factory = (T) factoryMap.get(clazz);
            if (factory == null) {
                final Properties props = loadProps(clazz);
                final String implClassName = props.getProperty("defaultImpl");
                final Class<? extends T> implClass = (Class<? extends T>) Class.forName(implClassName, true,
                                                                                       clazz.getClassLoader());
                factory = implClass.newInstance();
                factoryMap.put(clazz, factory);
            }
        } catch (final Exception e) {
            throw new AbstractFactoryException("Error on attempt to newPair the factory.", e);
        }
        return factory;
    }
}