public class AuditInterceptor extends EmptyInterceptor {
    public boolean onFlushDirty(Object entity, Serializable id,
            Object[] currentState, Object[] previousState,
            String[] propertyNames, Type[] types) {
        if (entity instanceof IAuditable) {
            for (int i = 0; i < propertyNames.length; i++) {
                if ("createdSignature".equals(propertyNames[i])) {
                    currentState[i] = createSignature();
                    return true;
                }
            }
        }
        return false;
    }

    public boolean onSave(Object entity, Serializable id, Object[] state,
            String[] propertyNames, Type[] types) {
        if (entity instanceof IAuditable) {
            for (int i = 0; i < propertyNames.length; i++) {
                if ("createdSignature".equals(propertyNames[i])) {
                    state[i] = createSignature();
                    return true;
                }
            }
        }
        return false;
    }

    private UserSignature createSignature() {
        UserSignature signature = new UserSignature();
        String assignID;
        try {
            assignID = SessionManager.getSession(
                    SecurityContext.getInstance().getSessionId())
                    .getMainAssignmentID();
        } catch (NoSessionException ex) {
            throw new HibernateException(ex);
        }
        signature.setAssignmentId(assignID);
        signature.setDate(Calendar.getInstance());
        return signature;
    }
}

   public boolean onSave(.....) {
      for(int i = 0; i < state.length; i++) {
         if(types != null && types[i] instanceof ComponentType) {
            handleComponentInsert(state[i]);
            continue;
         }

         ....
      }
   }

   public void onDelete(.....) {
      for(int i = 0; i < state.length; i++) {
         if(types != null && types[i] instanceof ComponentType) {
            handleComponentDelete(state[i]);
            continue;
         }


         .....
      }
   }

   public boolean onFlushDirty(.....) {
      for (int i = 0; i < currentState.length; i++) {
         if(types != null && types[i] instanceof ComponentType) {
            handleComponentDirty(previousState[i], currentState[i]);
            continue;
         }

         .....
      }
   }
   
   /**
    * Helper method that onSave() can call when it encounters a ComponentType. This method
    * organizes data about the component and calls onSave(component), since Hibernate
    * does not do this automatically.
    *
    * @param component the Component that's being inserted
    */
   private void handleComponentInsert(Object component) {
      try {
         String[] propertyNames = getPropertyNames(component);
         Object[] state = getState(component);
         this.onSave(component, null, state, propertyNames, null);
      } catch(Exception e) {
         logger.error("An error occurred while handling a component insertion in the Audit Trail", e);
      }
   }   
   
   
   /**
    * Helper method that onFlushDirty() can call when it encounters a ComponentType. This method
    * organizes data about the component and calls onFlushDirty(), since Hibernate
    * does not do this automatically.
    *
    * @param priorComponent the previous state of the Component
    * @param newComponent the current state of the Component
    */
   private void handleComponentDirty(Object priorComponent, Object newComponent) {
      try {
         String[] propertyNames = getPropertyNames(priorComponent);
         Object[] previousState = getState(priorComponent);
         Object[] currentState = getState(newComponent);
         
         this.onFlushDirty(newComponent, null, currentState, previousState, propertyNames, null);
      } catch(Exception e) {
         logger.error("An error occurred while handling a dirty component in the Audit Trail", e);
      }
   }
   
   /**
    * Helper method that onDelete() can call when it encounters a ComponentType. This method
    * organizes data about the component and calls onDelete(), since Hibernate
    * does not do this automatically.
    *
    * @param component the Component that's being deleted
    */
   private void handleComponentDelete(Object component) {
      //Object entity, Serializable id, Object[] state, String[] propertyNames, Type[] types
      try {
         String[] propertyNames = getPropertyNames(component);
         Object[] state = getState(component);
         this.onDelete(component, null, state, propertyNames, null);
      } catch(Exception e) {
         logger.error("An error occurred while handling a component insertion in the Audit Trail", e);
      }
   }
   
   /**
    * Gets all of the property values for a bean
    *
    * @param o the object whose getters will be called
    * @return the property values for a bean
    *
    * @throws IntrospectionException
    * @throws IllegalAccessException
    * @throws InvocationTargetException
    */
   private Object[] getState(Object o) throws IntrospectionException, IllegalAccessException, InvocationTargetException {
      BeanInfo bi = Introspector.getBeanInfo(o.getClass());
      PropertyDescriptor[] descriptors = bi.getPropertyDescriptors();
      
      Object[] states = new Object[descriptors.length];
      for(int i = 0; i < descriptors.length; i++) {
         Method m = descriptors[i].getReadMethod();
         
         states[i] = m.invoke(o, null);
      }
      
      return states;
   }
   
   /**
    * This method discovers all of the property names for a bean
    *
    * @param o the object whose properties will be discovered
    * @return the property names
    *
    * @throws IntrospectionException
    */
   private String[] getPropertyNames(Object o) throws IntrospectionException {
      //Use an Introspector to get all of the PropertyDescriptors
      BeanInfo bi = Introspector.getBeanInfo(o.getClass());
      PropertyDescriptor[] descriptors = bi.getPropertyDescriptors();
      
      //Use the PropertyDescriptors to get the name of each bean property
      String[] names = new String[descriptors.length];
      for(int i = 0; i < descriptors.length; i++) {
         names[i] = descriptors[i].getName();
      }
      return names;
   }