// Copyright 2008, 2010 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package org.apache.tapestry5.hibernate;
import java.util.List;
import org.apache.tapestry5.grid.GridDataSource;
import org.apache.tapestry5.grid.SortConstraint;
import org.hibernate.Criteria;
import org.hibernate.Session;
import org.hibernate.criterion.Order;
import org.hibernate.criterion.Projections;
/**
* A simple implementation of {@link org.apache.tapestry5.grid.GridDataSource} based on a Hibernate Session and a known
* entity class. This implementation does support multiple {@link org.apache.tapestry5.grid.SortConstraint sort
* constraints}; however it assumes a direct mapping from sort constraint property to Hibernate property.
* <p/>
* This class is <em>not</em> thread-safe; it maintains internal state.
* <p/>
* Typically, an instance of this object is created fresh as needed (that is, it is not stored between requests).
*/
public class HibernateGridDataSource implements GridDataSource
{
private final Session session;
private final Class entityType;
private int startIndex;
private List preparedResults;
public HibernateGridDataSource(Session session, Class entityType)
{
assert session != null;
assert entityType != null;
this.session = session;
this.entityType = entityType;
}
/**
* Returns the total number of rows for the configured entity type.
*/
@Override
public int getAvailableRows()
{
Criteria criteria = session.createCriteria(entityType);
applyAdditionalConstraints(criteria);
criteria.setProjection(Projections.rowCount());
Number result = (Number) criteria.uniqueResult();
return result.intValue();
}
/**
* Prepares the results, performing a query (applying the sort results, and the provided start and end index). The
* results can later be obtained from {@link #getRowValue(int)} }.
*
* @param startIndex index, from zero, of the first item to be retrieved
* @param endIndex index, from zero, of the last item to be retrieved
* @param sortConstraints zero or more constraints used to set the order of the returned values
*/
@Override
public void prepare(int startIndex, int endIndex, List<SortConstraint> sortConstraints)
{
assert sortConstraints != null;
Criteria crit = session.createCriteria(entityType);
crit.setFirstResult(startIndex).setMaxResults(endIndex - startIndex + 1);
for (SortConstraint constraint : sortConstraints)
{
String propertyName = constraint.getPropertyModel().getPropertyName();
switch (constraint.getColumnSort())
{
case ASCENDING:
crit.addOrder(Order.asc(propertyName));
break;
case DESCENDING:
crit.addOrder(Order.desc(propertyName));
break;
default:
}
}
applyAdditionalConstraints(crit);
this.startIndex = startIndex;
preparedResults = crit.list();
}
/**
* Invoked after the main criteria has been set up (firstResult, maxResults and any sort contraints). This gives
* subclasses a chance to apply additional constraints before the list of results is obtained from the criteria.
* This implementation does nothing and may be overridden.
*/
protected void applyAdditionalConstraints(Criteria crit)
{
}
/**
* Returns a row value at the given index (which must be within the range defined by the call to {@link
* #prepare(int, int, java.util.List)} ).
*
* @param index of object
* @return object at that index
*/
@Override
public Object getRowValue(int index)
{
return preparedResults.get(index - startIndex);
}
/**
* Returns the entity type, as provided via the constructor.
*/
@Override
public Class getRowType()
{
return entityType;
}
}