package org.trails.page;

 import ognl.Ognl;

 import ognl.OgnlException;

 import org.trails.TrailsRuntimeException;

 import org.trails.descriptor.IClassDescriptor;

 import org.trails.exception.EmptyModelException;

 /**

  * A page which has a model object.

  *

  * @author Chris Nelson

  */

 public abstract class ModelPage extends TrailsPage

 {

         public abstract Object getModel();

         public abstract void setModel(Object model);

         protected boolean isModelNew(Object model)

         {

                 try

                 {

                         return Ognl.getValue(getClassDescriptor().getIdentifierDescriptor().getName(), model) == null;

                 } catch (OgnlException e)

                 {

                         throw new TrailsRuntimeException(e);

                 }

         }

         public boolean isModelNew()

         {

                 return isModelNew(getModel());

         }

         public IClassDescriptor getClassDescriptor()

         {

                 if (getModel() == null) throw new EmptyModelException("Model does not exist");

                 return getDescriptorService().getClassDescriptor(getModel().getClass());

         }

 }