foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/config/ResultType.java

/*
 * Copyright (c) 1998, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     James Sutherland - initial impl
package org.eclipse.persistence.config;

import org.eclipse.persistence.sessions.DataRecord;

/**
 * Result type hint values.
 *
 * The class contains all the valid values for QueryHints.RESULT_TYPE query hint.
 * By default in JPA for non-single select queries an Array of values is returned.
 * If getSingleResult() is called the first array is returned, for getResultList() a List of arrays is returned.
 * <p>i.e. "Select e.firstName, e.lastName from Employee e" returns {@literal List<Object[]>}
 * <p>or the native query, "SELECT * FROM EMPLOYEE" returns {@literal List<Object[]>}
 * <p>The ResultType can be used to instead return a Map of values (DatabaseRecord, ReportQueryResult).
 * <p>It can also be used to return a single column, or single value.
 *
 * JPA Query Hint Usage:
 *
 * <p><code>query.setHint(QueryHints.RESULT_TYPE, ResultType.Map);</code>
 * <p>or
 * <p><code>@QueryHint(name=QueryHints.RESULT_TYPE, value=ResultType.Map)</code>
 *
 * <p>Hint values are case-insensitive.
 * "" could be used instead of default value ResultType.Array.
 *
 * @see QueryHints#RESULT_TYPE
 * @see DataRecord
 * @see org.eclipse.persistence.sessions.DatabaseRecord
 * @see org.eclipse.persistence.queries.ReportQueryResult
 * @see org.eclipse.persistence.queries.ReportQuery#setReturnType(int)
 * @see org.eclipse.persistence.queries.DataReadQuery#setResultType
 *
 * @author James Sutherland
 */
public class ResultType {
    /**
     * An Object array of values is returned {@literal (List<Object[]> or Object[])}.
     */
    public static final String  Array = "Array";

    /**
     * A Map of key value pairs is returned.
     * For a native queries the keys are the column names, ({@literal List<DatabaseRecord>}, or DatabaseRecord).
     * For JPQL queries the keys are the attribute names, ({@literal List<ReportQueryResult>}, or ReportQueryResult).
     */
    public static final String  Map = "Map";

    /**
     * A List of the first selected value is returned.
     */
    public static final String  Attribute = "Attribute";

    /**
     * The first value of the first rows is returned.
     */
    public static final String  Value = "Value";


    /**
     * The default type is Array.
     */
    public static final String DEFAULT = Array;
}