Java tutorial
/* Index ECM Engine - A system for managing the capture (when created * or received), classification (cataloguing), storage, retrieval, * revision, sharing, reuse and disposition of documents. * * Copyright (C) 2008 Regione Piemonte * Copyright (C) 2008 Provincia di Torino * Copyright (C) 2008 Comune di Torino * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version 2, * or (at your option) any later version. * * 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 General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. * */ package it.doqui.index.ecmengine.client.engine; import it.doqui.index.ecmengine.client.engine.exception.EcmEngineDelegateInstantiationException; import it.doqui.index.ecmengine.client.engine.util.EcmEngineDelegateConstants; import java.lang.reflect.Constructor; import java.lang.reflect.InvocationTargetException; import java.util.ResourceBundle; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; /** * Classe factory utilizzabile per caricare una nuova istanza * del client delegate dei servizi di gestione e ricerca di contenuti. * * <p>Questa classe non è istanziabile, ma fornisce un metodo * {@code static} che restituisce la nuova istanza. Alcuni dei parametri * di funzionamento della factory sono definiti nell'interfaccia * {@link EcmEngineDelegateConstants}, altri vengono caricati da * un file di proprietà il cui nome predefinito è * {@code ecmengine-engine-delegate.properties} * (vedere anche {@link EcmEngineDelegateConstants#ECMENGINE_PROPERTIES_FILE}). * * @author Doqui * * @see EcmEngineDelegateConstants#ECMENGINE_PROPERTIES_FILE */ public class EcmEngineDelegateFactory implements EcmEngineDelegateConstants { /** * Costruttore protected definito per nascondere il costruttore * pubblico di default poiché la classe non deve essere * istanziabile. */ protected EcmEngineDelegateFactory() { throw new UnsupportedOperationException(); } /** * Metodo factory che crea una nuova istanza del client delegate. * * <p>La factory cerca di istanziare la classe di implementazione * specificata dall'utente nel file di proprietà * {@code ecmengine-engine-delegate.properties}. Se tale operazione fallisce * la factory cerca di istanziare la classe di default definita * in {@link it.doqui.index.ecmengine.client.engine.util.EcmEngineDelegateConstants#ECMENGINE_DELEGATE_CLASS_NAME_DEFAULT}. * </p> * * @return Una nuova istanza del client delegate. * * @throws EcmEngineDelegateInstantiationException Se si verifica un * errore nell'istanziazione del client delegate. */ public static EcmEngineDelegate getEcmEngineDelegate() throws EcmEngineDelegateInstantiationException { final ResourceBundle resources = ResourceBundle.getBundle(ECMENGINE_PROPERTIES_FILE); final String caller = resources.getString(ECMENGINE_DELEGATE_CALLER); final Log logger = LogFactory.getLog(caller + ECMENGINE_DELEGATE_LOG_CATEGORY); final String implClass = resources.getString(ECMENGINE_DELEGATE_CLASS); EcmEngineDelegate ecmEngineDelegateImpl = null; logger.debug("[EcmEngineDelegateFactory::getEcmEngineDelegate] BEGIN"); logger.debug("[EcmEngineDelegateFactory::getEcmEngineDelegate] " + "Classe delegate: " + implClass); try { ecmEngineDelegateImpl = getClassInstance(implClass, logger); } catch (EcmEngineDelegateInstantiationException e) { logger.warn("[EcmEngineDelegateFactory::getEcmEngineDelegate] " + "Impossibile caricare la classe \"" + implClass + "\": " + e.getMessage()); logger.debug("[EcmEngineDelegateFactory::getEcmEngineDelegate] " + "Classe delegate di default: " + ECMENGINE_DELEGATE_CLASS_NAME_DEFAULT); try { ecmEngineDelegateImpl = getClassInstance(ECMENGINE_DELEGATE_CLASS_NAME_DEFAULT, logger); } catch (EcmEngineDelegateInstantiationException ex) { logger.error("[EcmEngineDelegateFactory::getEcmEngineDelegate] " + "Impossibile caricare la classe di default \"" + ECMENGINE_DELEGATE_CLASS_NAME_DEFAULT + "\": " + ex.getMessage()); throw ex; // Rilancia l'eccezione al chiamante } } finally { logger.debug("[EcmEngineDelegateFactory::getEcmEngineDelegate] END"); } return ecmEngineDelegateImpl; } private static EcmEngineDelegate getClassInstance(String ecmEngineDelegateImplName, Log logger) throws EcmEngineDelegateInstantiationException { EcmEngineDelegate classInstance = null; logger.debug("[EcmEngineDelegateFactory::getClassInstance] BEGIN"); try { logger.debug("[EcmEngineDelegateFactory::getClassInstance] " + "Caricamento classe: " + ecmEngineDelegateImplName); final Class delegateClass = Class.forName(ecmEngineDelegateImplName); final Constructor constructor = delegateClass.getConstructor(new Class[] { Log.class }); classInstance = (EcmEngineDelegate) constructor.newInstance(new Object[] { logger }); } catch (ClassNotFoundException e) { logger.error("[EcmEngineDelegateFactory::getClassInstance] " + "FATAL: classe non trovata."); throw new EcmEngineDelegateInstantiationException("Classe non trovata.", e); } catch (NoSuchMethodException e) { logger.error( "[EcmEngineDelegateFactory::getClassInstance] " + "FATAL: nessun costruttore compatibile."); throw new EcmEngineDelegateInstantiationException("Nessun costruttore compatibile.", e); } catch (InstantiationException e) { logger.error("[EcmEngineDelegateFactory::getClassInstance] " + "FATAL: errore di istanziazione."); throw new EcmEngineDelegateInstantiationException("Errore di istanziazione.", e); } catch (IllegalAccessException e) { logger.error("[EcmEngineDelegateFactory::getClassInstance] " + "FATAL: errore di accesso."); throw new EcmEngineDelegateInstantiationException("Errore di accesso.", e); } catch (InvocationTargetException e) { logger.error("[EcmEngineDelegateFactory::getClassInstance] " + "FATAL: eccezione nel target invocato."); throw new EcmEngineDelegateInstantiationException("Eccezione nel target invocato.", e); } finally { logger.debug("[EcmEngineDelegateFactory::getClassInstance] END"); } return classInstance; } }