| package org.apache.lucene.analysis; |
| |
| /* |
| * 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. |
| */ |
| |
| import java.io.IOException; |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| import java.util.List; |
| |
| import org.apache.lucene.util.AttributeSource; |
| |
| /** |
| * This class can be used if the token attributes of a TokenStream |
| * are intended to be consumed more than once. It caches |
| * all token attribute states locally in a List. |
| * |
| * <P>CachingTokenFilter implements the optional method |
| * {@link TokenStream#reset()}, which repositions the |
| * stream to the first Token. |
| */ |
| public final class CachingTokenFilter extends TokenFilter { |
| private List<AttributeSource.State> cache = null; |
| private Iterator<AttributeSource.State> iterator = null; |
| private AttributeSource.State finalState; |
| |
| /** |
| * Create a new CachingTokenFilter around <code>input</code>, |
| * caching its token attributes, which can be replayed again |
| * after a call to {@link #reset()}. |
| */ |
| public CachingTokenFilter(TokenStream input) { |
| super(input); |
| } |
| |
| @Override |
| public final boolean incrementToken() throws IOException { |
| if (cache == null) { |
| // fill cache lazily |
| cache = new LinkedList<>(); |
| fillCache(); |
| iterator = cache.iterator(); |
| } |
| |
| if (!iterator.hasNext()) { |
| // the cache is exhausted, return false |
| return false; |
| } |
| // Since the TokenFilter can be reset, the tokens need to be preserved as immutable. |
| restoreState(iterator.next()); |
| return true; |
| } |
| |
| @Override |
| public final void end() { |
| if (finalState != null) { |
| restoreState(finalState); |
| } |
| } |
| |
| /** |
| * Rewinds the iterator to the beginning of the cached list. |
| * <p> |
| * Note that this does not call reset() on the wrapped tokenstream ever, even |
| * the first time. You should reset() the inner tokenstream before wrapping |
| * it with CachingTokenFilter. |
| */ |
| @Override |
| public void reset() { |
| if(cache != null) { |
| iterator = cache.iterator(); |
| } |
| } |
| |
| private void fillCache() throws IOException { |
| while(input.incrementToken()) { |
| cache.add(captureState()); |
| } |
| // capture final state |
| input.end(); |
| finalState = captureState(); |
| } |
| |
| } |