// Copyright 2011 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.jpa;
import java.util.List;
import javax.persistence.EntityManager;
import javax.persistence.TypedQuery;
import javax.persistence.criteria.CriteriaBuilder;
import javax.persistence.criteria.CriteriaQuery;
import javax.persistence.criteria.Path;
import javax.persistence.criteria.Root;
import org.apache.tapestry5.grid.GridDataSource;
import org.apache.tapestry5.grid.SortConstraint;
/**
* A simple implementation of {@link org.apache.tapestry5.grid.GridDataSource} based on a
* {@linkplain javax.persistence.EntityManager} and a known
* entity class. This implementation does support multiple
* {@link org.apache.tapestry5.grid.SortConstraint sort
* constraints}.
* <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).
*
* @since 5.3
*/
public class JpaGridDataSource<E> implements GridDataSource
{
private final EntityManager entityManager;
private final Class<E> entityType;
private int startIndex;
private List<E> preparedResults;
public JpaGridDataSource(final EntityManager entityManager, final Class<E> entityType)
{
super();
this.entityManager = entityManager;
this.entityType = entityType;
}
/**
* {@inheritDoc}
*/
@Override
public int getAvailableRows()
{
final CriteriaBuilder builder = entityManager.getCriteriaBuilder();
CriteriaQuery<Long> criteria = builder.createQuery(Long.class);
final Root<E> root = criteria.from(entityType);
criteria = criteria.select(builder.count(root));
applyAdditionalConstraints(criteria, root, builder);
return entityManager.createQuery(criteria).getSingleResult().intValue();
}
/**
* {@inheritDoc}
*/
@Override
public void prepare(final int startIndex, final int endIndex,
final List<SortConstraint> sortConstraints)
{
final CriteriaBuilder builder = entityManager.getCriteriaBuilder();
final CriteriaQuery<E> criteria = builder.createQuery(entityType);
final Root<E> root = criteria.from(entityType);
applyAdditionalConstraints(criteria.select(root), root, builder);
for (final SortConstraint constraint : sortConstraints)
{
final String propertyName = constraint.getPropertyModel().getPropertyName();
final Path<Object> propertyPath = root.get(propertyName);
switch (constraint.getColumnSort())
{
case ASCENDING:
criteria.orderBy(builder.asc(propertyPath));
break;
case DESCENDING:
criteria.orderBy(builder.desc(propertyPath));
break;
default:
}
}
final TypedQuery<E> query = entityManager.createQuery(criteria);
query.setFirstResult(startIndex);
query.setMaxResults(endIndex - startIndex + 1);
this.startIndex = startIndex;
preparedResults = query.getResultList();
}
protected void applyAdditionalConstraints(final CriteriaQuery<?> criteria, final Root<E> root,
final CriteriaBuilder builder)
{
}
/**
* {@inheritDoc}
*/
@Override
public Object getRowValue(final int index)
{
return preparedResults.get(index - startIndex);
}
/**
* {@inheritDoc}
*/
@Override
public Class<E> getRowType()
{
return entityType;
}
}