package org.apache.lucene.analysis.shingle;
/**
* 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.io.Reader;
import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.util.Version;
/**
* A ShingleAnalyzerWrapper wraps a {@link ShingleFilter} around another {@link Analyzer}.
* <p>
* A shingle is another name for a token based n-gram.
* </p>
*/
public final class ShingleAnalyzerWrapper extends Analyzer {
private final Analyzer defaultAnalyzer;
private int maxShingleSize = ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE;
private int minShingleSize = ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE;
private String tokenSeparator = ShingleFilter.TOKEN_SEPARATOR;
private boolean outputUnigrams = true;
public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer) {
super();
this.defaultAnalyzer = defaultAnalyzer;
}
public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer, int maxShingleSize) {
this(defaultAnalyzer);
setMaxShingleSize(maxShingleSize);
}
public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer, int minShingleSize, int maxShingleSize) {
this(defaultAnalyzer);
setMaxShingleSize(maxShingleSize);
setMinShingleSize(minShingleSize);
}
/**
* Wraps {@link StandardAnalyzer}.
*/
public ShingleAnalyzerWrapper(Version matchVersion) {
super();
this.defaultAnalyzer = new StandardAnalyzer(matchVersion);
}
/**
* Wraps {@link StandardAnalyzer}.
*/
public ShingleAnalyzerWrapper(Version matchVersion, int minShingleSize, int maxShingleSize) {
this(matchVersion);
setMaxShingleSize(maxShingleSize);
setMinShingleSize(minShingleSize);
}
/**
* The max shingle (token ngram) size
*
* @return The max shingle (token ngram) size
*/
public int getMaxShingleSize() {
return maxShingleSize;
}
/**
* Set the maximum size of output shingles (default: 2)
*
* @param maxShingleSize max shingle size
*/
public void setMaxShingleSize(int maxShingleSize) {
if (maxShingleSize < 2) {
throw new IllegalArgumentException("Max shingle size must be >= 2");
}
this.maxShingleSize = maxShingleSize;
}
/**
* The min shingle (token ngram) size
*
* @return The min shingle (token ngram) size
*/
public int getMinShingleSize() {
return minShingleSize;
}
/**
* <p>Set the min shingle size (default: 2).
* <p>This method requires that the passed in minShingleSize is not greater
* than maxShingleSize, so make sure that maxShingleSize is set before
* calling this method.
*
* @param minShingleSize min size of output shingles
*/
public void setMinShingleSize(int minShingleSize) {
if (minShingleSize < 2) {
throw new IllegalArgumentException("Min shingle size must be >= 2");
}
if (minShingleSize > maxShingleSize) {
throw new IllegalArgumentException
("Min shingle size must be <= max shingle size");
}
this.minShingleSize = minShingleSize;
}
public String getTokenSeparator() {
return tokenSeparator;
}
/**
* Sets the string to use when joining adjacent tokens to form a shingle
* @param tokenSeparator used to separate input stream tokens in output shingles
*/
public void setTokenSeparator(String tokenSeparator) {
this.tokenSeparator = (tokenSeparator == null ? "" : tokenSeparator);
}
public boolean isOutputUnigrams() {
return outputUnigrams;
}
/**
* Shall the filter pass the original tokens (the "unigrams") to the output
* stream?
*
* @param outputUnigrams Whether or not the filter shall pass the original
* tokens to the output stream
*/
public void setOutputUnigrams(boolean outputUnigrams) {
this.outputUnigrams = outputUnigrams;
}
@Override
public TokenStream tokenStream(String fieldName, Reader reader) {
TokenStream wrapped;
try {
wrapped = defaultAnalyzer.reusableTokenStream(fieldName, reader);
} catch (IOException e) {
wrapped = defaultAnalyzer.tokenStream(fieldName, reader);
}
ShingleFilter filter = new ShingleFilter(wrapped, minShingleSize, maxShingleSize);
filter.setMinShingleSize(minShingleSize);
filter.setMaxShingleSize(maxShingleSize);
filter.setTokenSeparator(tokenSeparator);
filter.setOutputUnigrams(outputUnigrams);
return filter;
}
private class SavedStreams {
TokenStream wrapped;
ShingleFilter shingle;
}
@Override
public TokenStream reusableTokenStream(String fieldName, Reader reader) throws IOException {
SavedStreams streams = (SavedStreams) getPreviousTokenStream();
if (streams == null) {
streams = new SavedStreams();
streams.wrapped = defaultAnalyzer.reusableTokenStream(fieldName, reader);
streams.shingle = new ShingleFilter(streams.wrapped);
setPreviousTokenStream(streams);
} else {
TokenStream result = defaultAnalyzer.reusableTokenStream(fieldName, reader);
if (result == streams.wrapped) {
/* the wrapped analyzer reused the stream */
streams.shingle.reset();
} else {
/* the wrapped analyzer did not, create a new shingle around the new one */
streams.wrapped = result;
streams.shingle = new ShingleFilter(streams.wrapped);
}
}
streams.shingle.setMaxShingleSize(maxShingleSize);
streams.shingle.setMinShingleSize(minShingleSize);
streams.shingle.setTokenSeparator(tokenSeparator);
streams.shingle.setOutputUnigrams(outputUnigrams);
return streams.shingle;
}
}