/*
    * EL4J, the Extension Library for the J2EE, adds incremental enhancements to
    * the spring framework, http://el4j.sf.net
    * Copyright (C) 2010 by ELCA Informatique SA, Av. de la Harpe 22-24,
    * 1000 Lausanne, Switzerland, http://www.elca.ch
    *
    * EL4J is published under the GNU Lesser General Public License (LGPL)
    * Version 2.1. See http://www.gnu.org/licenses/
    *
   * 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 Lesser General Public License for more details.
   *
   * For alternative licensing, please contact info@elca.ch
   */
  package ch.elca.el4j.services.persistence.jpa.dao;
  
  import java.lang.reflect.Method;
  
  import javax.persistence.EntityManagerFactory;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.springframework.beans.BeansException;
  import org.springframework.beans.factory.config.BeanPostProcessor;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextAware;
  import org.springframework.core.Ordered;
  import org.springframework.core.PriorityOrdered;
  
  import ch.elca.el4j.services.persistence.generic.dao.GenericDao;
  import ch.elca.el4j.services.persistence.jpa.dao.extentstrategies.ExtentFetcher;
  import ch.elca.el4j.util.codingsupport.Reject;
  
  /**
   * Inject the ExtentFetcher in GenericDaos.
   * It gets the extentFetcher from the spring context
   * by using the default name {@link EXTENT_FETCHER_BEAN_DEFAULT_NAME}.
   *
   * @svnLink $Revision: 4253 $;$Date: 2010-12-21 11:08:04 +0100 (Di, 21. Dez 2010) $;$Author: swismer $;$URL: https://el4j.svn.sourceforge.net/svnroot/el4j/branches/el4j_3_1/el4j/framework/modules/hibernate/src/main/java/ch/elca/el4j/services/persistence/jpa/dao/JpaExtentFetcherInjectorBeanPostProcessor.java $
   *
   * @author Simon Stelling (SST)
   */
  public class JpaExtentFetcherInjectorBeanPostProcessor
  		implements BeanPostProcessor, PriorityOrdered, ApplicationContextAware {
  
  	/**
  	 * The default name for the property of the session factory.
  	 */
  	public static final String EXTENT_FETCHER_BEAN_DEFAULT_NAME = "extentFetcher";
  	
  	/**
  	 * private logger.
  	 */
  	private static final Logger s_logger = LoggerFactory.getLogger(JpaExtentFetcherInjectorBeanPostProcessor.class);
  	
  	/**
  	 * Caches the 'extentFetcher' bean from the application context. 
  	 */
  	protected ExtentFetcher extentFetcher;
  	
  	/**
  	 * the order of this BeanPostProcessor.
  	 */
  	private int order = Ordered.LOWEST_PRECEDENCE;
  
  	/**
  	 * The ApplicationContext from which the extentFetcher bean is obtained.
  	 */
  	private ApplicationContext m_applicationContext;
  	
  	/**
  	 * Initiates the real work.
  	 * @param bean the bean to postprocess
  	 * @param beanName the name of the bean
  	 * @return the bean
  	 * @throws BeansException
  	 */
  	public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
  		s_logger.debug("Treating bean with name:" + beanName);
  		if (GenericJpaDao.class.isAssignableFrom(bean.getClass())) {
  			s_logger.debug("init dao with name:" + beanName);
  			initDao((GenericJpaDao<?, ?>) bean);
  		}
  		return bean;
  	}
  
  	/** {@inheritDoc} */
  	public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
  		return bean;
  	}
  
  
  	/**
  	 * Try to inject the extentFetcher into the given dao.
  	 * @param dao the dao to inject the extentFetcher
  	 */
  	protected void initDao(GenericJpaDao<?, ?> dao) {
 		if (getExtentFetcher() != null) {
 			try {
 				Method setter = dao.getClass().getMethod(
 					"setExtentFetcher", ExtentFetcher.class);
 				setter.invoke(dao, getExtentFetcher());
 				s_logger.debug("value set in dao");
 				
 			} catch (Exception e) {
 				// ignore problems
 				s_logger.error("problem when auto-setting extentFetcher", e);
 
 			}
 		} else {
 			s_logger.error("no extentFetcher available -- cannot use extent-based fetch methods");
 		}
 	}
 
 	/**
 	 * Gets the session factory (from spring context if needed).
 	 * @return the extentFetcher
 	 */
 	public ExtentFetcher getExtentFetcher() {
 		if ((extentFetcher == null) && (m_applicationContext != null)) {
 			// try to locate the session factory
 			if (m_applicationContext.containsBean(EXTENT_FETCHER_BEAN_DEFAULT_NAME)) {
 				extentFetcher = (ExtentFetcher)
 					m_applicationContext.getBean(EXTENT_FETCHER_BEAN_DEFAULT_NAME);
 			} else {
 				s_logger.error("failed to obtain extentFetcher from application context "
 					+ "-- cannot use Extent-based fetching");
 			}
 		}
 		return extentFetcher;
 	}
 
 	/**
 	 * If you do not set the extent fetcher explicitly,
 	 * it will be obtained from the application's context.
 	 * @param extentFetcher the fetcher to use
 	 */
 	public void setExtentFetcher(ExtentFetcher extentFetcher) {
 		this.extentFetcher = extentFetcher;
 	}
 
 	/** {@inheritDoc} */
 	public void setOrder(int order) {
 		this.order = order;
 	}
 
 	/** {@inheritDoc} */
 	public int getOrder() {
 		return this.order;
 	}
 
 	/** {@inheritDoc} */
 	public void setApplicationContext(ApplicationContext applicationContext)
 		throws BeansException {
 		
 		m_applicationContext = applicationContext;
 	}
 }