org.hibernate.spatial.criterion.SpatialProjections.java Source code

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Here is the source code for org.hibernate.spatial.criterion.SpatialProjections.java

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/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
 * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
 */
package org.hibernate.spatial.criterion;

import org.hibernate.Criteria;
import org.hibernate.HibernateException;
import org.hibernate.criterion.CriteriaQuery;
import org.hibernate.criterion.Projection;
import org.hibernate.criterion.SimpleProjection;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.spatial.SpatialAggregate;
import org.hibernate.spatial.SpatialDialect;
import org.hibernate.type.Type;

/**
 * A factory for spatial projections.
 *
 * @author Karel Maesen
 */
public class SpatialProjections {

    private SpatialProjections() {
    }

    /**
     * Applies an extent projection to the specified geometry function
     * <p>
     * <p>The extent of a set of {@code Geometry}s is the union of their bounding boxes.</p>
     *
     * @param propertyName The property to use for calculating the extent
     *
     * @return an extent-projection for the specified property.
     */
    public static Projection extent(final String propertyName) {
        return new SimpleProjection() {

            public Type[] getTypes(Criteria criteria, CriteriaQuery criteriaQuery) throws HibernateException {
                return new Type[] { criteriaQuery.getType(criteria, propertyName) };
            }

            public String toSqlString(Criteria criteria, int position, CriteriaQuery criteriaQuery)
                    throws HibernateException {
                final StringBuilder stbuf = new StringBuilder();

                final SessionFactoryImplementor factory = criteriaQuery.getFactory();
                final String[] columns = criteriaQuery.getColumnsUsingProjection(criteria, propertyName);
                final Dialect dialect = factory.getDialect();
                if (dialect instanceof SpatialDialect) {
                    final SpatialDialect seDialect = (SpatialDialect) dialect;
                    stbuf.append(seDialect.getSpatialAggregateSQL(columns[0], SpatialAggregate.EXTENT));
                    stbuf.append(" as y").append(position).append('_');
                    return stbuf.toString();
                }
                return null;
            }

        };

    }

}