TeeTokenFilter.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;

import java.io.IOException;


/**
 * Works in conjunction with the SinkTokenizer to provide the ability to set aside tokens
 * that have already been analyzed.  This is useful in situations where multiple fields share
 * many common analysis steps and then go their separate ways.
 * <p/>
 * It is also useful for doing things like entity extraction or proper noun analysis as
 * part of the analysis workflow and saving off those tokens for use in another field.
 *
 * <pre>
SinkTokenizer sink1 = new SinkTokenizer();
SinkTokenizer sink2 = new SinkTokenizer();

TokenStream source1 = new TeeTokenFilter(new TeeTokenFilter(new WhitespaceTokenizer(reader1), sink1), sink2);
TokenStream source2 = new TeeTokenFilter(new TeeTokenFilter(new WhitespaceTokenizer(reader2), sink1), sink2);

TokenStream final1 = new LowerCaseFilter(source1);
TokenStream final2 = source2;
TokenStream final3 = new EntityDetect(sink1);
TokenStream final4 = new URLDetect(sink2);

d.add(new Field("f1", final1));
d.add(new Field("f2", final2));
d.add(new Field("f3", final3));
d.add(new Field("f4", final4));
 * </pre>
 * In this example, <code>sink1</code> and <code>sink2<code> will both get tokens from both
 * <code>reader1</code> and <code>reader2</code> after whitespace tokenizer
 * and now we can further wrap any of these in extra analysis, and more "sources" can be inserted if desired.
 * It is important, that tees are consumed before sinks (in the above example, the field names must be
 * less the sink's field names).
 * Note, the EntityDetect and URLDetect TokenStreams are for the example and do not currently exist in Lucene
 <p/>
 *
 * See <a href="http://issues.apache.org/jira/browse/LUCENE-1058">LUCENE-1058</a>.
 * <p/>
 * WARNING: {@link TeeTokenFilter} and {@link SinkTokenizer} only work with the old TokenStream API.
 * If you switch to the new API, you need to use {@link TeeSinkTokenFilter} instead, which offers 
 * the same functionality.

 * @see SinkTokenizer
 * @deprecated Use {@link TeeSinkTokenFilter} instead
 **/
public class TeeTokenFilter extends TokenFilter {
  SinkTokenizer sink;

  public TeeTokenFilter(TokenStream input, SinkTokenizer sink) {
    super(input);
    this.sink = sink;
  }
  
  public Token next(final Token reusableToken) throws IOException {
    assert reusableToken != null;
    Token nextToken = input.next(reusableToken);
    sink.add(nextToken);
    return nextToken;
  }

}