src/Lucene.Net.Analysis.Common/Analysis/Miscellaneous/PerFieldAnalyzerWrapper.cs

using System.Collections.Generic;

namespace Lucene.Net.Analysis.Miscellaneous
{

    /*
     * 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.
     */



    /// <summary>
    /// This analyzer is used to facilitate scenarios where different
    /// fields Require different analysis techniques.  Use the Map
    /// argument in <seealso cref="#PerFieldAnalyzerWrapper(Analyzer, java.util.Map)"/>
    /// to add non-default analyzers for fields.
    /// 
    /// <para>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>
    /// 
    /// </para>
    /// <para>In this example, StandardAnalyzer will be used for all fields except "firstname"
    /// and "lastname", for which KeywordAnalyzer will be used.
    /// 
    /// </para>
    /// <para>A PerFieldAnalyzerWrapper can be used like any other analyzer, for both indexing
    /// and query parsing.
    /// </para>
    /// </summary>
    public sealed class PerFieldAnalyzerWrapper : AnalyzerWrapper
    {
        private readonly Analyzer defaultAnalyzer;
        private readonly IDictionary<string, Analyzer> fieldAnalyzers;

        /// <summary>
        /// Constructs with default analyzer.
        /// </summary>
        /// <param name="defaultAnalyzer"> Any fields not specifically
        /// defined to use a different analyzer will use the one provided here. </param>
        public PerFieldAnalyzerWrapper(Analyzer defaultAnalyzer)
            : this(defaultAnalyzer, null)
        {
        }

        /// <summary>
        /// Constructs with default analyzer and a map of analyzers to use for 
        /// specific fields.
        /// </summary>
        /// <param name="defaultAnalyzer"> Any fields not specifically
        /// defined to use a different analyzer will use the one provided here. </param>
        /// <param name="fieldAnalyzers"> a Map (String field name to the Analyzer) to be 
        /// used for those fields  </param>
        public PerFieldAnalyzerWrapper(Analyzer defaultAnalyzer, IDictionary<string, Analyzer> fieldAnalyzers)
            : base(PER_FIELD_REUSE_STRATEGY)
        {
            this.defaultAnalyzer = defaultAnalyzer;
            this.fieldAnalyzers = fieldAnalyzers ?? new Dictionary<string, Analyzer>();
        }

        protected override Analyzer GetWrappedAnalyzer(string fieldName)
        {
            Analyzer analyzer = fieldAnalyzers.ContainsKey(fieldName) ?
                fieldAnalyzers[fieldName] :
                null;
            return analyzer ?? defaultAnalyzer;
        }

        public override string ToString()
        {
            return "PerFieldAnalyzerWrapper(" + fieldAnalyzers + ", default=" + defaultAnalyzer + ")";
        }
    }
}