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* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch 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.elasticsearch.index.similarity;
import org.apache.lucene.search.similarities.Normalization;
import org.apache.lucene.search.similarities.NormalizationH1;
import org.apache.lucene.search.similarities.NormalizationH2;
import org.apache.lucene.search.similarities.NormalizationH3;
import org.apache.lucene.search.similarities.NormalizationZ;
import org.elasticsearch.common.settings.Settings;
/**
* Abstract implementation of {@link SimilarityProvider} providing common behaviour
*/
public abstract class AbstractSimilarityProvider implements SimilarityProvider {
protected static final Normalization NO_NORMALIZATION = new Normalization.NoNormalization();
private final String name;
/**
* Creates a new AbstractSimilarityProvider with the given name
*
* @param name Name of the Provider
*/
protected AbstractSimilarityProvider(String name) {
this.name = name;
}
/**
* {@inheritDoc}
*/
@Override
public String name() {
return this.name;
}
/**
* Parses the given Settings and creates the appropriate {@link Normalization}
*
* @param settings Settings to parse
* @return {@link Normalization} referred to in the Settings
*/
protected Normalization parseNormalization(Settings settings) {
String normalization = settings.get("normalization");
if ("no".equals(normalization)) {
return NO_NORMALIZATION;
} else if ("h1".equals(normalization)) {
float c = settings.getAsFloat("normalization.h1.c", 1f);
return new NormalizationH1(c);
} else if ("h2".equals(normalization)) {
float c = settings.getAsFloat("normalization.h2.c", 1f);
return new NormalizationH2(c);
} else if ("h3".equals(normalization)) {
float c = settings.getAsFloat("normalization.h3.c", 800f);
return new NormalizationH3(c);
} else if ("z".equals(normalization)) {
float z = settings.getAsFloat("normalization.z.z", 0.30f);
return new NormalizationZ(z);
} else {
throw new IllegalArgumentException("Unsupported Normalization [" + normalization + "]");
}
}
}