EstimatorFactory.java

/**
 *  Copyright 2007-2015 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.estimate;

import edu.isi.pegasus.common.util.DynamicLoader;
import edu.isi.pegasus.planner.classes.ADag;
import edu.isi.pegasus.planner.classes.PegasusBag;
        
import edu.isi.pegasus.planner.common.PegasusProperties;


/**
 * Factory class to load the estimator.
 * 
 * @author Karan Vahi
 */
public class EstimatorFactory {
     /**
     * The default package where all the implementations reside.
     */
    public static final String DEFAULT_PACKAGE_NAME = "edu.isi.pegasus.planner.estimate";

    /**
     * The name of the class implementing default estimation strategy.
     */
    public static final String DEFAULT_ESTIMATOR_CLASS = "Default";

    

    /**
     * Loads the appropriate estimator.
     *
     * @param dag        the workflow being planned for.
     * @param bag        the bag of initialization objects.
     *
     * @return the instance of the appropriate Estimator.
     *
     * @throws EstimatorFactoryException that nests any error that
     *         might occur during the instantiation
     *
     * @see #DEFAULT_PACKAGE_NAME
     */
    public static Estimator loadEstimator( ADag dag,
                                           PegasusBag bag )
                                           
                                           throws EstimatorFactoryException{

        
        if( bag == null ){
            throw new EstimatorFactoryException( "Invalid instantiation with a null PegasusBag" );
        }
        PegasusProperties props = bag.getPegasusProperties();
        if( props == null ){
            throw new EstimatorFactoryException( "Invalid instantiation with a null Pegasus Properties" );
        }
        
        String implementor = props.getEstimator();
        if( implementor == null ){
            implementor = EstimatorFactory.DEFAULT_ESTIMATOR_CLASS;
        }
        
        //now load the estimator
        Estimator estimator = null;
        String className = implementor;
        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 );
            estimator = (Estimator) dl.instantiate( new Object[0] );
            estimator.initialize( dag, bag );
        }
        catch ( Exception e ){
            throw new EstimatorFactoryException( " Unable to instantiate estimator ",
                                                 className,
                                                 e );
        }
        return estimator;
    }




}