C#編寫了一個基於Lucene.Net的搜索引擎查詢通用工具類：SearchEngineUtil

　　最近由於工作原因，一直忙於公司的各種項目（大部份都是基於spring cloud的微服務項目），故有一段時間沒有與大家分享總結最近的技術研究成果的，其實最近我一直在不斷的深入研究學習Spring、Spring Boot、Spring Cloud的各種框架原理，同時也隨時關註著.NET CORE的發展情況及最新技術點，也在極客時間上訂閱相關的專欄，只要下班有空我都會去認真閱讀觀看，紙質書箱也買了一些，總之近一年都是在通過：微信技術公眾號（.NET、JAVA、演算法、前端等技術方向）、極客時間、技術書箱 不斷的吸取、借鑒他人之精華，從而不斷的充實提高自己的技術水平，所謂：學如逆水行舟，不進則退，工作中學習，學習後工作中運用，當然寫文章分享是一種總結，同時也是“溫故而知新”的最佳應用。

　　前面廢話說得有點多了，就直奔本文的主題內容，編寫一個基於Lucene.Net的搜索引擎查詢通用工具類：SearchEngineUtil，Lucene是什麼，見百度百科 ,重點是:Lucene是一個全文檢索引擎的架構，提供了完整的查詢引擎和索引引擎，Lucene.NET是C#及.NET運行時下的另一種語言的實現，官網地址：http://lucenenet.apache.org/  ，具體用法就不多說了，官網以及網上都有很多，但由於Lucene.Net的原生SDK中的API比較複雜，用起來不太方便，故我進行了適當的封裝，把常用的增、刪、改、查（分頁查）在保證靈活度的情況下進行了封裝，使得操作Lucene.Net變得相對簡單一些，代碼本身也不複雜，貼出完整的SearchEngineUtil代碼如下：

using Lucene.Net.Analysis.PanGu;
using Lucene.Net.Documents;
using Lucene.Net.Index;
using Lucene.Net.QueryParsers;
using Lucene.Net.Search;
using Lucene.Net.Store;
using NLog;
using PanGu;
using PanGu.HighLight;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Reflection;
using System.Text;

namespace CN.Zuowenjun.Blog.Common
{
    /// <summary>
    /// Lucene 搜索引擎實用工具類
    /// Author:zuowenjun
    /// </summary>
    public class SearchEngineUtil
    {

        /// <summary>
        /// 創建並添加索引記錄
        /// </summary>
        /// <typeparam name="TIndex"></typeparam>
        /// <param name="indexDir"></param>
        /// <param name="indexData"></param>
        /// <param name="setDocFiledsAction"></param>
        public static void AddIndex<TIndex>(string indexDir, TIndex indexData, Action<Document, TIndex> setDocFiledsAction)
        {
            //創建索引目錄
            if (!System.IO.Directory.Exists(indexDir))
            {
                System.IO.Directory.CreateDirectory(indexDir);
            }
            FSDirectory directory = FSDirectory.Open(new DirectoryInfo(indexDir), new NativeFSLockFactory());
            bool isUpdate = IndexReader.IndexExists(directory);
            if (isUpdate)
            {
                //如果索引目錄被鎖定（比如索引過程中程式異常退出），則首先解鎖
                if (IndexWriter.IsLocked(directory))
                {
                    IndexWriter.Unlock(directory);
                }
            }
            using (IndexWriter writer = new IndexWriter(directory, new PanGuAnalyzer(), !isUpdate, IndexWriter.MaxFieldLength.UNLIMITED))
            {
                Document document = new Document();

                setDocFiledsAction(document, indexData);

                writer.AddDocument(document);

                writer.Optimize();//優化索引
            }
        }

        /// <summary>
        /// 刪除索引記錄
        /// </summary>
        /// <param name="indexDir"></param>
        /// <param name="keyFiledName"></param>
        /// <param name="keyFileValue"></param>
        public static void DeleteIndex(string indexDir, string keyFiledName, object keyFileValue)
        {
            FSDirectory directory = FSDirectory.Open(new DirectoryInfo(indexDir), new NativeFSLockFactory());
            if (!IndexReader.IndexExists(directory))
            {
                return;
            }

            using (IndexWriter iw = new IndexWriter(directory, new PanGuAnalyzer(), IndexWriter.MaxFieldLength.UNLIMITED))
            {
                iw.DeleteDocuments(new Term(keyFiledName, keyFileValue.ToString()));
                iw.Optimize();//刪除文件後並非從磁碟中移除，而是生成一個.del的文件，需要調用Optimize方法來清除。在清除文件前可以使用UndeleteAll方法恢復
            }
        }

        /// <summary>
        /// 更新索引記錄
        /// </summary>
        /// <param name="indexDir"></param>
        /// <param name="keyFiledName"></param>
        /// <param name="keyFileValue"></param>
        /// <param name="doc"></param>
        public static void UpdateIndex(string indexDir, string keyFiledName, object keyFileValue, Document doc)
        {
            FSDirectory directory = FSDirectory.Open(new DirectoryInfo(indexDir), new NativeFSLockFactory());
            if (!IndexReader.IndexExists(directory))
            {
                return;
            }

            using (IndexWriter iw = new IndexWriter(directory, new PanGuAnalyzer(), IndexWriter.MaxFieldLength.UNLIMITED))
            {
                iw.UpdateDocument(new Term(keyFiledName, keyFileValue.ToString()), doc);
                iw.Optimize();
            }
        }

        /// <summary>
        /// 是否存在指定的索引文檔
        /// </summary>
        /// <param name="indexDir"></param>
        /// <param name="keyFiledName"></param>
        /// <param name="keyFileValue"></param>
        /// <returns></returns>
        public static bool ExistsDocument(string indexDir, string keyFiledName, object keyFileValue)
        {
            FSDirectory directory = FSDirectory.Open(new DirectoryInfo(indexDir), new NativeFSLockFactory());
            if (!IndexReader.IndexExists(directory))
            {
                return false;
            }

            var reader = IndexReader.Open(directory, true);

            return reader.DocFreq(new Term(keyFiledName, keyFileValue.ToString())) > 0;
        }

        /// <summary>
        /// 查詢索引匹配到的記錄
        /// </summary>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="indexDir"></param>
        /// <param name="buildQueryAction"></param>
        /// <param name="getSortFieldsFunc"></param>
        /// <param name="buildResultFunc"></param>
        /// <param name="topCount"></param>
        /// <param name="needHighlight"></param>
        /// <returns></returns>
        public static List<TResult> SearchIndex<TResult>(string indexDir, Func<BooleanQuery, IDictionary<string, string>> buildQueryAction,
            Func<IEnumerable<SortField>> getSortFieldsFunc, Func<Document, TResult> buildResultFunc, bool needHighlight = true, int topCount = 0)
        {
            FSDirectory directory = FSDirectory.Open(new DirectoryInfo(indexDir), new NoLockFactory());

            if (!IndexReader.IndexExists(directory))
            {
                return new List<TResult>();
            }

            IndexReader reader = IndexReader.Open(directory, true);
            IndexSearcher searcher = new IndexSearcher(reader);

            BooleanQuery bQuery = new BooleanQuery();
            var keyWords = buildQueryAction(bQuery);

            Sort sort = null;
            var sortFields = getSortFieldsFunc();
            if (sortFields != null)
            {
                sort = new Sort();
                sort.SetSort(sortFields.ToArray());
            }

            topCount = topCount > 0 ? topCount : int.MaxValue;//當未指定TOP值，則設置最大值以表示獲取全部
            TopDocs resultDocs = null;
            if (sort != null)
            {
                resultDocs = searcher.Search(bQuery, null, topCount, sort);
            }
            else
            {
                resultDocs = searcher.Search(bQuery, null, topCount);
            }

            if (topCount > resultDocs.TotalHits)
            {
                topCount = resultDocs.TotalHits;
            }

            Dictionary<string, PropertyInfo> highlightProps = null;
            List<TResult> results = new List<TResult>();
            if (resultDocs != null)
            {
                for (int i = 0; i < topCount; i++)
                {
                    Document doc = searcher.Doc(resultDocs.ScoreDocs[i].Doc);
                    var model = buildResultFunc(doc);
                    if (needHighlight)
                    {
                        model = SetHighlighter(keyWords, model, ref highlightProps);
                    }

                    results.Add(model);
                }
            }

            return results;

        }

        /// <summary>
        /// 分頁查詢索引匹配到的記錄
        /// </summary>
        /// <typeparam name="TResult"></typeparam>
        /// <param name="indexDir"></param>
        /// <param name="buildQueryAction"></param>
        /// <param name="getSortFieldsFunc"></param>
        /// <param name="buildResultFunc"></param>
        /// <param name="pageSize"></param>
        /// <param name="page"></param>
        /// <param name="totalCount"></param>
        /// <param name="needHighlight"></param>
        /// <returns></returns>
        public static List<TResult> SearchIndexByPage<TResult>(string indexDir, Func<BooleanQuery, IDictionary<string, string>> buildQueryAction,
            Func<IEnumerable<SortField>> getSortFieldsFunc, Func<Document, TResult> buildResultFunc, int pageSize, int page, out int totalCount, bool needHighlight = true)
        {
            FSDirectory directory = FSDirectory.Open(new DirectoryInfo(indexDir), new NoLockFactory());

            if (!IndexReader.IndexExists(directory))
            {
                totalCount = 0;
                return new List<TResult>();
            }

            IndexReader reader = IndexReader.Open(directory, true);
            IndexSearcher searcher = new IndexSearcher(reader);

            BooleanQuery bQuery = new BooleanQuery();
            var keyWords = buildQueryAction(bQuery);

            Sort sort = null;
            var sortFields = getSortFieldsFunc();
            if (sortFields != null)
            {
                sort = new Sort();
                sort.SetSort(sortFields.ToArray());
            }

            TopScoreDocCollector docCollector = TopScoreDocCollector.Create(1, true);
            searcher.Search(bQuery, docCollector);
            totalCount = docCollector.TotalHits;

            if (totalCount <= 0) return null;

            TopDocs resultDocs = searcher.Search(bQuery, null, pageSize * page, sort);

            Dictionary<string, PropertyInfo> highlightProps = null;
            List<TResult> results = new List<TResult>();
            int indexStart = (page - 1) * pageSize;
            int indexEnd = indexStart + pageSize;
            if (totalCount < indexEnd) indexEnd = totalCount;

            if (resultDocs != null)
            {
                for (int i = indexStart; i < indexEnd; i++)
                {
                    Document doc = searcher.Doc(resultDocs.ScoreDocs[i].Doc);
                    var model = buildResultFunc(doc);
                    if (needHighlight)
                    {
                        model = SetHighlighter(keyWords, model, ref highlightProps);
                    }

                    results.Add(model);
                }
            }

            return results;
        }



        /// <summary>
        /// 設置結果高亮
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="dicKeywords"></param>
        /// <param name="model"></param>
        /// <param name="props"></param>
        /// <returns></returns>
        private static T SetHighlighter<T>(IDictionary<string, string> dicKeywords, T model, ref Dictionary<string, PropertyInfo> props)
        {
            SimpleHTMLFormatter simpleHTMLFormatter = new SimpleHTMLFormatter("<font color=\"red\">", "</font>");
            Highlighter highlighter = new Highlighter(simpleHTMLFormatter, new Segment());
            highlighter.FragmentSize = 250;

            Type modelType = typeof(T);
            foreach (var item in dicKeywords)
            {
                if (!string.IsNullOrWhiteSpace(item.Value))
                {
                    if (props == null)
                    {
                        props = new Dictionary<string, PropertyInfo>();
                    }

                    if (!props.ContainsKey(item.Key))
                    {
                        props[item.Key] = modelType.GetProperty(item.Key, BindingFlags.IgnoreCase | BindingFlags.Public | BindingFlags.Instance);
                    }

                    var modelProp = props[item.Key];
                    if (modelProp.PropertyType == typeof(string))
                    {
                        string newValue = highlighter.GetBestFragment(item.Value, modelProp.GetValue(model).ToString());
                        if (!string.IsNullOrEmpty(newValue))
                        {
                            modelProp.SetValue(model, newValue);
                        }
                    }
                }
            }

            return model;
        }


        /// <summary>
        /// 拆分關鍵詞
        /// </summary>
        /// <param name="keywords"></param>
        /// <returns></returns>
        public static string GetKeyWordsSplitBySpace(string keyword)
        {
            PanGuTokenizer ktTokenizer = new PanGuTokenizer();
            StringBuilder result = new StringBuilder();
            ICollection<WordInfo> words = ktTokenizer.SegmentToWordInfos(keyword);
            foreach (WordInfo word in words)
            {
                if (word == null)
                {
                    continue;
                }
                result.AppendFormat("{0}^{1}.0 ", word.Word, (int)Math.Pow(3, word.Rank));
            }
            return result.ToString().Trim();
        }

        /// <summary>
        /// 【輔助方法】創建盤古查詢對象
        /// </summary>
        /// <param name="field"></param>
        /// <param name="keyword"></param>
        /// <returns></returns>
        public static Query CreatePanGuQuery(string field, string keyword, bool needSplit = true)
        {
            if (needSplit)
            {
                keyword = GetKeyWordsSplitBySpace(keyword);
            }

            QueryParser parse = new QueryParser(Lucene.Net.Util.Version.LUCENE_30, field, new PanGuAnalyzer());
            parse.DefaultOperator = QueryParser.Operator.OR;
            Query query = parse.Parse(keyword);
            return query;
        }

        /// <summary>
        /// 【輔助方法】創建盤古多欄位查詢對象
        /// </summary>
        /// <param name="keyword"></param>
        /// <param name="fields"></param>
        /// <returns></returns>
        public static Query CreatePanGuMultiFieldQuery(string keyword, bool needSplit, params string[] fields)
        {
            if (needSplit)
            {
                keyword = GetKeyWordsSplitBySpace(keyword);
            }

            QueryParser parse = new MultiFieldQueryParser(Lucene.Net.Util.Version.LUCENE_30, fields, new PanGuAnalyzer());
            parse.DefaultOperator = QueryParser.Operator.OR;
            Query query = parse.Parse(keyword);
            return query;
        }

    }
}

　裡面除了使用了Lucene.Net nuget包，還單獨引用了PanGu分詞器及其相關組件，因為大多數情況下我們的內容會包含中文。如上代碼就不再細講了，註釋得比較清楚了。下麵貼出一些實際的用法：

創建索引：

 SearchEngineUtil.AddIndex(GetSearchIndexDir(), post, (doc, data) => BuildPostSearchDocument(data, doc));


        private Document BuildPostSearchDocument(Post post, Document doc = null)
        {

            if (doc == null)
            {
                doc = new Document();//創建Document
            }

            doc.Add(new Field("Id", post.Id.ToString(), Field.Store.YES, Field.Index.NOT_ANALYZED));
            doc.Add(new Field("Title", post.Title, Field.Store.YES, Field.Index.ANALYZED));
            doc.Add(new Field("Summary", post.Summary, Field.Store.YES, Field.Index.ANALYZED));
            doc.Add(new Field("CreateTime", post.CreateTime.ToString("yyyy/MM/dd HH:mm"), Field.Store.YES, Field.Index.NO));
            doc.Add(new Field("Author", post.IsOriginal ? (post.Creator ?? userQueryService.FindByName(post.CreateBy)).NickName : post.SourceBy, Field.Store.YES, Field.Index.NO));

            return doc;
        }

　刪除索引：

 SearchEngineUtil.DeleteIndex(GetSearchIndexDir(), "Id", post.Id);

　更新索引：

SearchEngineUtil.UpdateIndex(GetSearchIndexDir(), "Id", post.Id, BuildPostSearchDocument(post));

　分頁查詢：

               var keyword = SearchEngineUtil.GetKeyWordsSplitBySpace("夢在旅途 中國夢");
                var searchResult = SearchEngineUtil.SearchIndexByPage(indexDir, (bQuery) =>
                {
                    var query = SearchEngineUtil.CreatePanGuMultiFieldQuery(keyword, false, "Title", "Summary");
                    bQuery.Add(query, Occur.SHOULD);
                    return new Dictionary<string, string> {
                    { "Title",keyword},{"Summary",keyword}
                    };
                }, () =>
                {
                    return new[] { new SortField("Id", SortField.INT, true) };
                }, doc =>
                {
                    return new PostSearchInfoDto
                    {
                        Id = doc.Get("Id"),
                        Title = doc.Get("Title"),
                        Summary = doc.Get("Summary"),
                        Author = doc.Get("Author"),
                        CreateTime = doc.Get("CreateTime")
                    };

                }, pageSize, pageNo, out totalCount);

其它的還有：判斷索引中的指定文檔記錄存不存在、查詢符合條件的索引文檔等在此沒有列出，大家有興趣的可以COPY到自己的項目中測試一下。

這裡可以看一下我在自己的項目中(個人全新改版的自己博客，還在開發中)應用搜索場景的效果：

最後說明的是：Lucene並不是一個完整的全文檢索引擎，但瞭解它對於學習elasticsearch、solr還是有一定的幫助，目前一般應用於實際的生產項目中，多半是使用更高層的elasticsearch、solr。

 (本文中的代碼我是今年很早前就寫好了，只是今天才分享出來)

我喜歡對一些常用的組件進行封裝，比如過往封裝有：

基於MongoDb官方C#驅動封裝MongoDbCsharpHelper類（CRUD類）

基於RabbitMQ.Client組件實現RabbitMQ可復用的 ConnectionPool（連接池）