PPSFactory.java

/**
 *  Copyright 2007-2008 University Of Southern California
 *
 *  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 edu.isi.pegasus.planner.provenance.pasoa.pps;

import edu.isi.pegasus.planner.common.PegasusProperties;
import edu.isi.pegasus.common.util.DynamicLoader;

import edu.isi.pegasus.planner.provenance.pasoa.PPS;

/**
 * The factory for instantiating an XMLProducer.
 *
 * @author Karan Vahi
 * @version $Revision$
 */
public class PPSFactory {

    /**
     * The default package where all the implementations reside.
     */
    public static final String DEFAULT_PACKAGE_NAME = "edu.isi.pegasus.planner.provenance.pasoa.pps";


    /**
     * The default PPS implementation to be used.
     */
    public static final String DEFAULT_PPS_PROVIDER = "Empty";

    /**
     * The default Pasoa PPS implementation to be used.
     */
    public static final String PASOA_PPS_PROVIDER = "Pasoa";


    /**
     * The singleton instance of the PPS implementation that is returned.
     */
    private static PPS mInstance = null;


    /**
     * Loads the appropriate PPS implementation on the basis of the property set in the
     * properties.
     *
     *
     * @param properties the <code>PegasusProperties</code> object containing all
     *                   the properties required by Pegasus.
     *
     * @return the instance of the appropriate XML Producer.
     *
     * @throws PPSFactoryException that nests any error that
     *         might occur during the instantiation
     *
     * @see #DEFAULT_PACKAGE_NAME
     */
    public static PPS loadPPS( PegasusProperties properties )
                                              throws PPSFactoryException{

        //sanity check
        if( properties == null ){
            throw new PPSFactoryException( "No properties passed to factory " );
        }


        //check for singleton
        if( mInstance != null ){
            return mInstance;
        }


        String className = properties.getRefinementProvenanceStore();
        if( className == null ){
            className = DEFAULT_PPS_PROVIDER;
        }
        else if ( className.equalsIgnoreCase( "pasoa" ) ){
            className = PASOA_PPS_PROVIDER;
        }

        PPS pps = null;
        try{
            //prepend the package name if required
            className = ( className.indexOf('.') == -1 )?
                        //pick up from the default package
                        DEFAULT_PACKAGE_NAME + "." + className:
                        //load directly
                        className;

            //try loading the class dynamically
            DynamicLoader dl = new DynamicLoader( className );
            pps = ( PPS ) dl.instantiate( new Object[0] );
        }
        catch( Exception e ){
            throw new PPSFactoryException( " Unable to instantiate PPS ",
                                                 className,
                                                 e );
        }
        mInstance = pps;
        return pps;
    }


}