lucene/core/src/java/org/apache/lucene/analysis/tokenattributes/TermToBytesRefAttribute.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.tokenattributes;


import org.apache.lucene.util.Attribute;
import org.apache.lucene.util.BytesRef;

/**
 * This attribute is requested by TermsHashPerField to index the contents.
 * This attribute can be used to customize the final byte[] encoding of terms.
 * <p>
 * Consumers of this attribute call {@link #getBytesRef()} for each term. Example:
 * <pre class="prettyprint">
 *   final TermToBytesRefAttribute termAtt = tokenStream.getAttribute(TermToBytesRefAttribute.class);
 *
 *   while (tokenStream.incrementToken() {
 *     final BytesRef bytes = termAtt.getBytesRef();
 *
 *     if (isInteresting(bytes)) {
 *     
 *       // because the bytes are reused by the attribute (like CharTermAttribute's char[] buffer),
 *       // you should make a copy if you need persistent access to the bytes, otherwise they will
 *       // be rewritten across calls to incrementToken()
 *
 *       doSomethingWith(BytesRef.deepCopyOf(bytes));
 *     }
 *   }
 *   ...
 * </pre>
 * @lucene.internal This is a very expert and internal API, please use
 * {@link CharTermAttribute} and its implementation for UTF-8 terms; to
 * index binary terms, use {@link BytesTermAttribute} and its implementation.
 */
public interface TermToBytesRefAttribute extends Attribute {
  
  /**
   * Retrieve this attribute's BytesRef. The bytes are updated from the current term.
   * The implementation may return a new instance or keep the previous one.
   * @return a BytesRef to be indexed (only stays valid until token stream gets incremented)
   */
  public BytesRef getBytesRef();
}