D-Net

package eu.dnetlib.dhp.wf.importer.facade;

import static eu.dnetlib.dhp.wf.importer.ImportWorkflowRuntimeParameters.IMPORT_FACADE_FACTORY_CLASS;

import java.lang.reflect.Constructor;

import java.util.Map;

import org.apache.commons.lang.StringUtils;

import org.apache.hadoop.conf.Configuration;

import com.google.common.collect.ImmutableMap;

import eu.dnetlib.dhp.wf.importer.ImportWorkflowRuntimeParameters;

/**

 * Service facade utility methods.

 * @author mhorst

 *

 */

public final class ServiceFacadeUtils {

    //------------------------ CONSTRUCTORS -------------------

    private ServiceFacadeUtils() {}

    //------------------------ LOGIC --------------------------

    /**

     * Instantiates service based on provided parameters.

     * 

     * Service factory class name is mandatory and has to be provided as {@value ImportWorkflowRuntimeParameters#IMPORT_FACADE_FACTORY_CLASS} parameter.

     * Other parameters will be used by factory itself. Factory must be instantiable with no-argument construtor.

     * 

     * @param parameters set of parameters required for service instantiation

     * 

     */

    public static <T> T instantiate(Map<String, String> parameters) throws ServiceFacadeException {

        String serviceFactoryClassName = parameters.get(IMPORT_FACADE_FACTORY_CLASS);

        if (StringUtils.isBlank(serviceFactoryClassName)) {

            throw new ServiceFacadeException("unknown service facade factory, no " + IMPORT_FACADE_FACTORY_CLASS + " parameter provided!");

        }

        try {

            Class<?> clazz = Class.forName(serviceFactoryClassName);

            Constructor<?> constructor = clazz.getConstructor();

            @SuppressWarnings("unchecked")

            ServiceFacadeFactory<T> serviceFactory = (ServiceFacadeFactory<T>) constructor.newInstance();

            return serviceFactory.instantiate(parameters);    

        } catch (Exception e) {

            throw new ServiceFacadeException("exception occurred while instantiating service by facade factory: " + IMPORT_FACADE_FACTORY_CLASS, e);

        }

    }

    /**

     * Instantiates service based on provided configuration.

     * 

     * Service factory class name is mandatory and has to be provided as {@value ImportWorkflowRuntimeParameters#IMPORT_FACADE_FACTORY_CLASS} configuration entry.

     * Other parameters will be used by factory itself. Factory must be instantiable with no-argument construtor.

     * 

     * @param config set of configuration entries required for service instantiation

     */

    public static <T> T instantiate(Configuration config) throws ServiceFacadeException {

        return instantiate(buildParameters(config));

    }

    // ------------------------ PRIVATE --------------------------

    /**

     * Converts configuration entries into plain map.

     */

    private static Map<String, String> buildParameters(Configuration config) {

        ImmutableMap.Builder<String, String> builder = ImmutableMap.builder();

        for (Map.Entry<String, String> entry : config) {

          builder.put(entry);

        }

        return builder.build();

    }

}