lucene/analysis/common/src/java/org/apache/lucene/analysis/miscellaneous/KeywordRepeatFilterFactory.java

/*
 * 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.lucene.analysis.miscellaneous;

import java.util.Map;
import org.apache.lucene.analysis.TokenFilterFactory;
import org.apache.lucene.analysis.TokenStream;

/**
 * Factory for {@link KeywordRepeatFilter}.
 *
 * <p>Since {@link KeywordRepeatFilter} emits two tokens for every input token, and any tokens that
 * aren't transformed later in the analysis chain will be in the document twice. Therefore, consider
 * adding {@link RemoveDuplicatesTokenFilterFactory} later in the analysis chain.
 *
 * @since 4.3.0
 * @lucene.spi {@value #NAME}
 */
public final class KeywordRepeatFilterFactory extends TokenFilterFactory {

  /** SPI name */
  public static final String NAME = "keywordRepeat";

  /** Creates a new KeywordRepeatFilterFactory */
  public KeywordRepeatFilterFactory(Map<String, String> args) {
    super(args);
    if (!args.isEmpty()) {
      throw new IllegalArgumentException("Unknown parameters: " + args);
    }
  }

  /** Default ctor for compatibility with SPI */
  public KeywordRepeatFilterFactory() {
    throw defaultCtorException();
  }

  @Override
  public TokenStream create(TokenStream input) {
    return new KeywordRepeatFilter(input);
  }
}