org.hibernate.transform.DistinctRootEntityResultTransformer.java Source code

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Here is the source code for org.hibernate.transform.DistinctRootEntityResultTransformer.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.transform;

import java.util.List;

/**
 * Much like {@link RootEntityResultTransformer}, but we also distinct
 * the entity in the final result.
 * <p/>
 * Since this transformer is stateless, all instances would be considered equal.
 * So for optimization purposes we limit it to a single, singleton {@link #INSTANCE instance}.
 *
 * @author Gavin King
 * @author Steve Ebersole
 */
public class DistinctRootEntityResultTransformer implements TupleSubsetResultTransformer {

    public static final DistinctRootEntityResultTransformer INSTANCE = new DistinctRootEntityResultTransformer();

    /**
     * Disallow instantiation of DistinctRootEntityResultTransformer.
     */
    private DistinctRootEntityResultTransformer() {
    }

    /**
     * Simply delegates to {@link RootEntityResultTransformer#transformTuple}.
     *
     * @param tuple The tuple to transform
     * @param aliases The tuple aliases
     * @return The transformed tuple row.
     */
    @Override
    public Object transformTuple(Object[] tuple, String[] aliases) {
        return RootEntityResultTransformer.INSTANCE.transformTuple(tuple, aliases);
    }

    /**
     * Simply delegates to {@link DistinctResultTransformer#transformList}.
     *
     * @param list The list to transform.
     * @return The transformed List.
     */
    @Override
    public List transformList(List list) {
        return DistinctResultTransformer.INSTANCE.transformList(list);
    }

    @Override
    public boolean[] includeInTransform(String[] aliases, int tupleLength) {
        return RootEntityResultTransformer.INSTANCE.includeInTransform(aliases, tupleLength);
    }

    @Override
    public boolean isTransformedValueATupleElement(String[] aliases, int tupleLength) {
        return RootEntityResultTransformer.INSTANCE.isTransformedValueATupleElement(null, tupleLength);
    }

    /**
     * Serialization hook for ensuring singleton uniqueing.
     *
     * @return The singleton instance : {@link #INSTANCE}
     */
    private Object readResolve() {
        return INSTANCE;
    }

}