org.hibernate.shards.strategy.exit.AggregateExitOperation.java Source code

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Here is the source code for org.hibernate.shards.strategy.exit.AggregateExitOperation.java

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/**
 * Copyright (C) 2007 Google Inc.
 *
 * This library 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 2.1 of the License, or (at your option) any later version.
    
 * This library 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 this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
 */

package org.hibernate.shards.strategy.exit;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.criterion.AggregateProjection;

import java.math.BigDecimal;
import java.util.Collections;
import java.util.List;

/**
 * @author Maulik Shah
 */
public class AggregateExitOperation implements ProjectionExitOperation {

    private final SupportedAggregations aggregate;

    private final String fieldName;

    private final Log log = LogFactory.getLog(getClass());

    private enum SupportedAggregations {

        SUM("sum"), MIN("min"), MAX("max");

        private final String aggregate;

        private SupportedAggregations(String s) {
            this.aggregate = s;
        }

        public String getAggregate() {
            return aggregate;
        }

    }

    public AggregateExitOperation(AggregateProjection projection) {
        /**
         * an aggregateProjection's toString returns
         * min( ..., max( ..., sum( ..., or avg( ...
         * we just care about the name of the function
         * which happens to be before the first left parenthesis
         */
        String projectionAsString = projection.toString();
        String aggregateName = projectionAsString.substring(0, projectionAsString.indexOf("("));
        this.fieldName = projectionAsString.substring(projectionAsString.indexOf("(") + 1,
                projectionAsString.indexOf(")"));
        try {
            this.aggregate = SupportedAggregations.valueOf(aggregateName.toUpperCase());
        } catch (IllegalArgumentException e) {
            log.error("Use of unsupported aggregate: " + aggregateName);
            throw e;
        }
    }

    public List<Object> apply(List<Object> results) {

        List<Object> nonNullResults = ExitOperationUtils.getNonNullList(results);

        switch (aggregate) {
        case MAX:
            return Collections
                    .singletonList((Object) Collections.max(ExitOperationUtils.getComparableList(nonNullResults)));
        case MIN:
            return Collections
                    .singletonList((Object) Collections.min(ExitOperationUtils.getComparableList(nonNullResults)));
        case SUM:
            return Collections.<Object>singletonList(getSum(nonNullResults, fieldName));
        default:
            log.error("Aggregation Projection is unsupported: " + aggregate);
            throw new UnsupportedOperationException("Aggregation Projection is unsupported: " + aggregate);
        }
    }

    private BigDecimal getSum(List<Object> results, String fieldName) {
        BigDecimal sum = new BigDecimal(0.0);
        for (Object obj : results) {
            Number num = getNumber(obj, fieldName);
            sum = sum.add(new BigDecimal(num.toString()));
        }
        return sum;
    }

    private Number getNumber(Object obj, String fieldName) {
        return (Number) ExitOperationUtils.getPropertyValue(obj, fieldName);
    }

}