package info.ejava.examples.ejb.tx.ejb;
   
   import info.ejava.examples.ejb.tx.bo.BeanCount;
   
   import javax.annotation.PostConstruct;
   import javax.annotation.PreDestroy;
   import javax.ejb.EJB;
   import javax.ejb.Stateless;
   import javax.ejb.TransactionAttribute;
  import javax.ejb.TransactionAttributeType;
  import javax.ejb.TransactionManagement;
  import javax.ejb.TransactionManagementType;
  import javax.persistence.EntityManager;
  import javax.persistence.LockModeType;
  import javax.persistence.PersistenceContext;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  @Stateless
  @TransactionManagement(TransactionManagementType.CONTAINER)
  public class WarehouseTxEJB {
      private static final Logger logger = LoggerFactory.getLogger(WarehouseTxEJB.class);
      
      @PersistenceContext(unitName="ejbtx-warehouse")
      private EntityManager em;
      
      @EJB
      private TxWatcherEJB txWatcher;
  
      @TransactionAttribute(TransactionAttributeType.REQUIRED)
      @PostConstruct
      public void init() {
          logger.debug("*** {}:init({}) ***", getClass().getSimpleName(), super.hashCode());
          txWatcher.watchTransaction(getClass(), super.hashCode());
          updateBeanCount(1);
      }
      @TransactionAttribute(TransactionAttributeType.REQUIRED)
      @PreDestroy
      public void destroy() {
          logger.debug("*** {}:destroy({}) ***", getClass().getSimpleName(), super.hashCode());
          txWatcher.watchTransaction(getClass(), super.hashCode());
          updateBeanCount(-1);
      }
      
      /**
       * This method will remove all data from all tables associated with the example
       * @return
       */
      @TransactionAttribute(TransactionAttributeType.REQUIRED)
      public int cleanup() {
          String entities[] = new String[]{ "Product", "Shipment"};
          int count=0;
          for (String entity : entities) {
              count+=em.createQuery(String.format("delete from %s", entity)).executeUpdate();
          }
          return count;
      }
      
      private void updateBeanCount(int value) {
          String beanName = getClass().getSimpleName();
          BeanCount count=em.find(BeanCount.class, 
                  beanName, 
                  LockModeType.PESSIMISTIC_WRITE);
          if (count!=null) {
              count.setCount(count.getCount()+value);
          } else {
              count = new BeanCount(beanName);
              count.setCount(value);
              em.persist(count);
          }
          logger.debug("updatedBeanCount({}) to {}", count.getName(), count.getCount());
      }
  }