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The Drools and jBPM internal API which is NOT backwards compatible between releases.

There is a newer version: 9.44.0.Final

/*
 * Copyright 2015 Red Hat, Inc. and/or its affiliates.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.kie.internal.utils;

import java.util.List;

/**
 * Variable indexer that allows to transform variable instance into other representation (usually string)
 * to be able to use it for queries.
 *
 * @param  type of the object that will represent indexed variable
 */
public interface VariableIndexer {

    /**
     * Tests if given variable shall be indexed by this indexer
     *
     * NOTE: only one indexer can be used for given variable
     *
     * @param variable variable to be indexed
     * @return true if variable should be indexed with this indexer
     */
    boolean accept(Object variable);

    /**
     * Performs index/transform operation of the variable. Result of this operation can be
     * either single value or list of values to support complex type separation.
     * For example when variable is of type Person that has name, address phone indexer could
     * build three entries out of it to represent individual fields:
     * person = person.name
     * address = person.address.street
     * phone = person.phone
     * that will allow more advanced queries to be used to find relevant entries.
     * @param name name of the variable
     * @param variable actual variable value
     * @return
     */
    List index(String name, Object variable);
}