package ejava.examples.webtier.jpa;
   
   import java.util.HashMap;
   import java.util.Map;
   import java.util.Properties;
   
   import javax.persistence.EntityManager;
   import javax.persistence.EntityManagerFactory;
   import javax.persistence.Persistence;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * This class is used to create and hold open EntityManagerFactory objects 
   * when not running within a Java EE environment.
   *
   * @author jcstaff
   */
  public class JPAUtil {
      private static final Log log = LogFactory.getLog(JPAUtil.class);
      private static final Map<String, EntityManagerFactory> factories = 
          new HashMap<String, EntityManagerFactory>();
      private static ThreadLocal<EntityManager> em = 
          new ThreadLocal<EntityManager>();
      private static Properties emfProperties = new Properties();
      
      /**
       * This method defines the properties to pass to createEntityManagerFactory
       */
      public static void setEntityManagerFactoryProperties(Properties props) {
          emfProperties = (Properties)props.clone();
      }
      
      /**
       * This method will create or return the EntityManagerFactory for 
       * the specified persistence unit.
       * 
       * @param puName matches value in persistence.xml
       * @return
       */
      public static EntityManagerFactory getEntityManagerFactory(String puName) {
          EntityManagerFactory emf = factories.get(puName);
          if (emf == null) {
              synchronized(factories) {
                  emf = factories.get(puName);
                  if (emf == null) {
                      log.debug("creating EntityManagerFactory(" + puName + ")");
                      emf = (emfProperties != null && emfProperties.size() > 0) ?
                              Persistence.createEntityManagerFactory(puName, 
                                      emfProperties) :
                              Persistence.createEntityManagerFactory(puName);                                
                      factories.put(puName, emf);
                  }
              }
          }
          return emf;
      }
          
      public static void setEntityManager(EntityManager emgr) {
          em.set(emgr);
      }    
  
      public static EntityManager getEntityManager(String puName) {
          EntityManager emgr = em.get();
          if (emgr == null) {
              synchronized (em) {
                  if (emgr == null) {
                      //okay-nobody gave us one, use JavaSE technique to get one
                      emgr = getEntityManagerFactory(puName).createEntityManager();
                      setEntityManager(emgr);
                  }
              }
          }
          return em.get();
      }
      public static EntityManager getEntityManager() {
          EntityManager emgr = em.get();
          if (emgr == null) {
              log.fatal("EntityManager not initialized for Thread!!!");
          }
          return em.get();
      }
      /**
       * This method just allows the caller to look at entity manager to see
       * if it is currently set.
       * @return
       */
      public static EntityManager peekEntityManager() {
          return em.get();
      }
      public static void closeEntityManager() {
          EntityManager emgr = em.get();
          if (emgr != null) {
              em.remove();
              emgr.close();
          }
      }
  
     
     /**
      * This method closes all EntityManagerFactory objects and clears them
      * from the cache.
      * 
      */
     public static void close() {
         log.debug("closing " + factories.size() + " EntityManagerFactories");
         synchronized(factories) {
             for(String puName : factories.keySet()) {
                 factories.get(puName).close();
                 log.debug(puName + " closed");
             }
             factories.clear();
         }
     }
     
     
 }