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Apache Solr (module: core)

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.solr.update.processor;

import java.lang.invoke.MethodHandles;
import java.util.Collection;
import java.util.function.Function;
import org.apache.solr.common.SolrInputField;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Abstract subclass of FieldMutatingUpdateProcessor for implementing UpdateProcessors that will
 * mutate all individual values of a selected field independently
 *
 * @see FieldMutatingUpdateProcessorFactory
 */
public abstract class FieldValueMutatingUpdateProcessor extends FieldMutatingUpdateProcessor {

  private static final Logger log = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

  public static final Object DELETE_VALUE_SINGLETON =
      new Object() {
        @Override
        public String toString() {
          return "!!Singleton Object Triggering Value Deletion!!";
        }
      };

  public FieldValueMutatingUpdateProcessor(
      FieldNameSelector selector, UpdateRequestProcessor next) {
    super(selector, next);
  }

  /**
   * Mutates individual values of a field as needed, or returns the original value.
   *
   * @param src a value from a matched field which should be mutated
   * @return the value to use as a replacement for src, or DELETE_VALUE_SINGLETON to
   *     indicate that the value should be removed completely.
   * @see #DELETE_VALUE_SINGLETON
   */
  protected abstract Object mutateValue(final Object src);

  @Override
  protected final SolrInputField mutate(final SolrInputField src) {
    Collection