org.apache.lucene.analysis.miscellaneous.PerFieldAnalyzerWrapper.java Source code

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Here is the source code for org.apache.lucene.analysis.miscellaneous.PerFieldAnalyzerWrapper.java

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/*
 * 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.miscellaneous;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.DelegatingAnalyzerWrapper;

import java.util.Collections;
import java.util.Map;

/**
 * This analyzer is used to facilitate scenarios where different
 * fields require different analysis techniques.  Use the Map
 * argument in {@link #PerFieldAnalyzerWrapper(Analyzer, java.util.Map)}
 * to add non-default analyzers for fields.
 * 
 * <p>Example usage:
 * 
 * <pre class="prettyprint">
 * {@code
 * Map<String,Analyzer> analyzerPerField = new HashMap<>();
 * analyzerPerField.put("firstname", new KeywordAnalyzer());
 * analyzerPerField.put("lastname", new KeywordAnalyzer());
 *
 * PerFieldAnalyzerWrapper aWrapper =
 *   new PerFieldAnalyzerWrapper(new StandardAnalyzer(version), analyzerPerField);
 * }
 * </pre>
 * 
 * <p>In this example, StandardAnalyzer will be used for all fields except "firstname"
 * and "lastname", for which KeywordAnalyzer will be used.
 * 
 * <p>A PerFieldAnalyzerWrapper can be used like any other analyzer, for both indexing
 * and query parsing.
 *
 * @since 3.1
 */
public final class PerFieldAnalyzerWrapper extends DelegatingAnalyzerWrapper {
    private final Analyzer defaultAnalyzer;
    private final Map<String, Analyzer> fieldAnalyzers;

    /**
     * Constructs with default analyzer.
     *
     * @param defaultAnalyzer Any fields not specifically
     * defined to use a different analyzer will use the one provided here.
     */
    public PerFieldAnalyzerWrapper(Analyzer defaultAnalyzer) {
        this(defaultAnalyzer, null);
    }

    /**
     * Constructs with default analyzer and a map of analyzers to use for 
     * specific fields.
     *
     * @param defaultAnalyzer Any fields not specifically
     * defined to use a different analyzer will use the one provided here.
     * @param fieldAnalyzers a Map (String field name to the Analyzer) to be 
     * used for those fields 
     */
    public PerFieldAnalyzerWrapper(Analyzer defaultAnalyzer, Map<String, Analyzer> fieldAnalyzers) {
        super(PER_FIELD_REUSE_STRATEGY);
        this.defaultAnalyzer = defaultAnalyzer;
        this.fieldAnalyzers = (fieldAnalyzers != null) ? fieldAnalyzers : Collections.<String, Analyzer>emptyMap();
    }

    @Override
    protected Analyzer getWrappedAnalyzer(String fieldName) {
        Analyzer analyzer = fieldAnalyzers.get(fieldName);
        return (analyzer != null) ? analyzer : defaultAnalyzer;
    }

    @Override
    public String toString() {
        return "PerFieldAnalyzerWrapper(" + fieldAnalyzers + ", default=" + defaultAnalyzer + ")";
    }
}