LogFormatterFactory.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.common.logging;


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





/**
 * A factory class to load the appropriate implementation of LogFormatter
 * as specified by properties.
 *
 * @author Karan Vahi
 * @version $Revision$
 */
public class LogFormatterFactory {

   
    /**
     * The default package where all the implementations reside.
     */
    public static final String DEFAULT_PACKAGE_NAME =
        "edu.isi.pegasus.common.logging.format";


    /**
     * Holds a singleton instance that is populated via the loadSingletonInstance() 
     * method.
     */
    private static LogFormatter mSingletonInstance;
  
    /**
     * Loads the appropriate LogFormatter class as specified by properties.
     * 
     * @param implementor  the name of the class implementing LogFormatter
     *
     * 
     * @return handle to the Log Formatter.
     *
     * @throws LogFormatterFactoryException that nests any error that
     *         might occur during the instantiation
     *
     * @see #DEFAULT_PACKAGE_NAME
     */
    public static LogFormatter loadSingletonInstance( String implementor ) throws
        LogFormatterFactoryException {
        
        return ( mSingletonInstance = ( mSingletonInstance == null )?
                                        loadInstance( implementor ):  
                                        mSingletonInstance 
                );
            
  
    }
    
    /**
     * Loads the appropriate LogFormatter class as specified by properties.
     * 
     * @param properties is an instance of properties to use.
     *
     * @return handle to the Log Formatter.
     *
     * @throws LogFormatterFactoryException that nests any error that
     *         might occur during the instantiation
     *
     * @see #DEFAULT_PACKAGE_NAME
     */
    public static LogFormatter loadInstance( PegasusProperties properties ) throws
        LogFormatterFactoryException {

        if( properties == null ){
            throw new LogFormatterFactoryException( "Invalid NULL properties passed" );
        }

        /* get the implementor from properties */
        String formatImplementor = properties.getLogFormatter().trim();

        /* prepend the package name if required */
        formatImplementor = ( formatImplementor.indexOf('.') == -1) ?
            //pick up from the default package
            DEFAULT_PACKAGE_NAME + "." + formatImplementor :
            //load directly
            formatImplementor;

       
        // determine the class that implements the site catalog
        return loadInstance( formatImplementor );
    }

    /**
     * Loads the Log Formatter specified.
     * 
     * @param implementor  the name of the class implementing LogFormatter
     *
     * @return handle to the Site Catalog.
     *
     * @throws LogFormatterFactoryException that nests any error that
     *         might occur during the instantiation
     *
     * @see #DEFAULT_PACKAGE_NAME
     */
    public  static LogFormatter loadInstance( String implementor ) throws
        LogFormatterFactoryException{
        
        
        LogFormatter result = null;
        try{
            if ( implementor == null ){
                throw new RuntimeException( "You need to specify the implementor " );
            }

            /* prepend the package name if required */
            implementor = ( implementor.indexOf('.') == -1) ?
                //pick up from the default package
                DEFAULT_PACKAGE_NAME + "." + implementor :
                //load directly
                implementor;

            DynamicLoader dl = new DynamicLoader( implementor );
            result = ( LogFormatter ) dl.instantiate( new Object[0] );

            if ( implementor == null ){
                throw new RuntimeException( "Unable to load " + implementor );
            }

        }
        catch( Exception e ){
            throw new LogFormatterFactoryException( "Unable to instantiate Log Formatter ",
                                            implementor,
                                            e );
        }
        
        return result;
    }

}