C#编写了一个基于Lucene.Net的搜索引擎查询通用工具类：SearchEngineUtil

　　最近由于工作原因，一直忙于公司的各种项目（大部份都是基于spring cloud的微服务项目），故有一段时间没有与大家分享总结最近的技术研究成果的，其实最近我一直在不断的深入研究学习Spring、Spring Boot、Spring Cloud的各种框架原理，同时也随时关注着.NET CORE的发展情况及最新技术点，也在极客时间上订阅相关的专栏，只要下班有空我都会去认真阅读观看，纸质书箱也买了一些，总之近一年都是在通过：微信技术公众号（.NET、JAVA、算法、前端等技术方向）、极客时间、技术书箱 不断的吸取、借鉴他人之精华，从而不断的充实提高自己的技术水平，所谓：学如逆水行舟，不进则退，工作中学习，学习后工作中运用，当然写文章分享是一种总结，同时也是“温故而知新”的最佳应用。

　　前面废话说得有点多了，就直奔本文的主题内容，编写一个基于Lucene.Net的搜索引擎查询通用工具类：SearchEngineUtil，Lucene是什么，见百度百科 ,重点是:Lucene是一个全文检索引擎的架构，提供了完整的查询引擎和索引引擎，Lucene.NET是C#及.NET运行时下的另一种语言的实现，官网地址：http://lucenenet.apache.org/  ，具体用法就不多说了，官网以及网上都有很多，但由于Lucene.Net的原生SDK中的API比较复杂，用起来不太方便，故我进行了适当的封装，把常用的增、删、改、查（分页查）在保证灵活度的情况下进行了封装，使得操作Lucene.Net变得相对简单一些，代码本身也不复杂，贴出完整的SearchEngineUtil代码如下：

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 搜索引擎实用工具类
    /// Author:zuowenjun
    /// </summary>
    public class SearchEngineUtil
    {

        /// <summary>
        /// 创建并添加索引记录
        /// </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)
        {
            //创建索引目录
            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)
            {
                //如果索引目录被锁定（比如索引过程中程序异常退出），则首先解锁
                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();//优化索引
            }
        }

        /// <summary>
        /// 删除索引记录
        /// </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();//删除文件后并非从磁盘中移除，而是生成一个.del的文件，需要调用Optimize方法来清除。在清除文件前可以使用UndeleteAll方法恢复
            }
        }

        /// <summary>
        /// 更新索引记录
        /// </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档
        /// </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>
        /// 查询索引匹配到的记录
        /// </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;//当未指定TOP值，则设置最大值以表示获取全部
            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>
        /// 分页查询索引匹配到的记录
        /// </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>
        /// 设置结果高亮
        /// </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>
        /// 拆分关键词
        /// </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>
        /// 【辅助方法】创建盘古查询对象
        /// </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>
        /// 【辅助方法】创建盘古多字段查询对象
        /// </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;
        }

    }
}

　里面除了使用了Lucene.Net nuget包，还单独引用了PanGu分词器及其相关组件，因为大多数情况下我们的内容会包含中文。如上代码就不再细讲了，注释得比较清楚了。下面贴出一些实际的用法：

创建索引：

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

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

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

　删除索引：

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

　更新索引：

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

　分页查询：

               var keyword = SearchEngineUtil.GetKeyWordsSplitBySpace("梦在旅途 中国梦");
                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);

其它的还有：判断索引中的指定文档记录存不存在、查询符合条件的索引文档等在此没有列出，大家有兴趣的可以COPY到自己的项目中测试一下。

这里可以看一下我在自己的项目中(个人全新改版的自己博客，还在开发中)应用搜索场景的效果：

最后说明的是：Lucene并不是一个完整的全文检索引擎，但了解它对于学习elasticsearch、solr还是有一定的帮助，目前一般应用于实际的生产项目中，多半是使用更高层的elasticsearch、solr。

(本文中的代码我是今年很早前就写好了，只是今天才分享出来)

我喜欢对一些常用的组件进行封装，比如过往封装有：

基于MongoDb官方C#驱动封装MongoDbCsharpHelper类（CRUD类）

基于RabbitMQ.Client组件实现RabbitMQ可复用的 ConnectionPool（连接池）