AbstractJpaDataProvider.java

/*
 * Copyright 2010, Andrew M Gibson
 *
 * www.andygibson.net
 *
 * This file is part of DataValve.
 *
 * DataValve is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 * 
 * DataValve is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 * 
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with DataValve.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package org.fluttercode.datavalve.provider.jpa;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.Query;

import org.fluttercode.datavalve.params.Parameter;
import org.fluttercode.datavalve.provider.AbstractQueryDataProvider;
import org.fluttercode.datavalve.provider.QueryDataProvider;
import org.fluttercode.datavalve.provider.util.DataQuery;

/**
 * Base class for a JPA based {@link QueryDataProvider}. Override and implement
 * {@link #createJpaQuery(String)} to create a query of the type needed.
 * 
 * @see JpaDataProvider
 * @see JpaNativeProvider
 * 
 * @author Andy Gibson
 * 
 * @param <T>
 */
public abstract class AbstractJpaDataProvider<T> extends
		AbstractQueryDataProvider<T> implements JpaDataProvider<T> {

	private static final long serialVersionUID = 1L;

	private EntityManager entityManager;

	public AbstractJpaDataProvider() {		
	}
	
	public AbstractJpaDataProvider(EntityManager entityManager) {
		super();
		this.entityManager = entityManager;
	}

	/**
	 * Override to create the specific type of query to use.
	 * 
	 * @see JpaDataProvider
	 * @see JpaNativeProvider
	 * 
	 * @param ql
	 *            Statement the query must execute (could be EJBQL or Native
	 *            depending on subclass)
	 * @return Query object created from the
	 *         {@link AbstractJpaDataProvider#entityManager} and configured with
	 *         the passed in sql.
	 */
	protected abstract Query createJpaQuery(String ql);

	public EntityManager getEntityManager() {
		return entityManager;
	}

	public void setEntityManager(EntityManager entityManager) {
		this.entityManager = entityManager;
	}

	/**
	 * Initializes a JPA {@link Query} using the passed in {@link DataQuery}.
	 * The type of query returned is determined from the
	 * {@link AbstractJpaDataProvider#createJpaQuery(String)} method which can
	 * return a native or EJBQL query depending on the subclass.
	 * 
	 * @param dataQuery
	 *            The {@link DataQuery} to initialize the query with
	 * @return The initialized {@link Query}
	 */
	private final Query buildJpaQuery(DataQuery dataQuery) {
		Query qry = createJpaQuery(dataQuery.getStatement());
		for (Parameter param : dataQuery.getParameters()) {
			qry.setParameter(param.getName(), param.getValue());
		}
		return qry;
	}

	@Override
	protected Integer queryForCount(DataQuery query) {
		Query qry = buildJpaQuery(query);
		Long result = (Long) qry.getSingleResult();
		return new Integer(result.intValue());
	}

	@SuppressWarnings("unchecked")
	@Override
	protected List<T> queryForResults(DataQuery query, Integer firstResult,
			Integer count) {
		Query qry = buildJpaQuery(query);
		if (firstResult != null) {
			qry.setFirstResult(firstResult.intValue());
		}

		if (count != null) {
			qry.setMaxResults(count);
		}

		return qry.getResultList();
	}
}