使用Lucene.NET实现简单的站内搜索

使用Lucene.NET实现简单的站内搜索

1. 导入Lucene.NET 开发包

   Lucene 是apache软件基金会一个开放源代码的全文检索引擎工具包，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，部分文本分析引擎。Lucene的目的是为软件开发人员提供一个简单易用的工具包，以方便的在目标系统中实现全文检索的功能，或者是以此为基础建立起完整的全文检索引擎。Lucene.Net 是 .NET 版的Lucene。

   你可以在这里下载到最新的Lucene.NET

2. 创建索引、更新索引、删除索引

   

3. 搜索，根据索引查找

   

    using System;
    using Lucene.Net.Store;
    using Lucene.Net.Index;
    using Lucene.Net.Analysis.PanGu;
    using Lucene.Net.Documents;
   
    namespace BLL
    {
        class IndexHelper
        {
            /// <summary>
            /// 日志小助手
            /// </summary>
            static Common.LogHelper logger = new Common.LogHelper(typeof(SearchBLL));
            /// <summary>
            /// 索引保存的位置，保存在配置文件中从配置文件读取
            /// </summary>
            static string indexPath = Common.ConfigurationHelper.AppSettingMapPath("IndexPath");
   
            /// <summary>
            /// 创建索引文件或更新索引文件
            /// </summary>
            /// <param name="item">索引信息</param>
            public static void CreateIndex(Model.HelperModel.IndexFileHelper item)
            {
                try
                {
                    //索引存储库
                    FSDirectory directory = FSDirectory.Open(new System.IO.DirectoryInfo(indexPath), new NativeFSLockFactory());
                    //判断索引是否存在
                    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))
                        {
                            //解锁索引库
                            IndexWriter.Unlock(directory);
                        }
                    }
                    //创建IndexWriter对象，添加索引
                    IndexWriter writer = new IndexWriter(directory, new PanGuAnalyzer(), !isUpdate, Lucene.Net.Index.IndexWriter.MaxFieldLength.UNLIMITED);
                    //获取新闻 title部分
                    string title = item.FileTitle;
                    //获取新闻主内容
                    string body = item.FileContent;
                    //为避免重复索引，所以先删除number=i的记录，再重新添加
                    //尤其是更新的话，更是必须要先删除之前的索引
                    writer.DeleteDocuments(new Term("id", item.FileName));
                    //创建索引文件 Document
                    Document document = new Document();
                    //只有对需要全文检索的字段才ANALYZED
                    //添加id字段
                    document.Add(new Field("id", item.FileName, Field.Store.YES, Field.Index.NOT_ANALYZED));
                    //添加title字段
                    document.Add(new Field("title", title, Field.Store.YES, Field.Index.NOT_ANALYZED));
                    //添加body字段
                    document.Add(new Field("body", body, Field.Store.YES, Field.Index.ANALYZED, Lucene.Net.Documents.Field.TermVector.WITH_POSITIONS_OFFSETS));
                    //添加url字段
                    document.Add(new Field("url", item.FilePath, Field.Store.YES, Field.Index.NOT_ANALYZED));
                    //写入索引库
                    writer.AddDocument(document);
                    //关闭资源
                    writer.Close();
                    //不要忘了Close，否则索引结果搜不到
                    directory.Close();
                    //记录日志
                    logger.Debug(String.Format("索引{0}创建成功",item.FileName));
                }
                catch (SystemException ex)
                {
                    //记录错误日志
                    logger.Error(ex);
                    throw;
                }
                catch (Exception ex)
                {
                    //记录错误日志
                    logger.Error(ex);
                    throw;
                }
            }
   
            /// <summary>
            /// 根据id删除相应索引
            /// </summary>
            /// <param name="guid">要删除的索引id</param>
            public static void DeleteIndex(string guid)
            {
                try
                {
                    ////索引存储库
                    FSDirectory directory = FSDirectory.Open(new System.IO.DirectoryInfo(indexPath), new NativeFSLockFactory());
                    //判断索引库是否存在索引
                    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);
                        }
                    }
                    IndexWriter writer = new IndexWriter(directory, new PanGuAnalyzer(), !isUpdate, Lucene.Net.Index.IndexWriter.MaxFieldLength.UNLIMITED);
                    //删除索引文件
                    writer.DeleteDocuments(new Term("id", guid));
                    writer.Close();
                    directory.Close();//不要忘了Close，否则索引结果搜不到
                    logger.Debug(String.Format("删除索引{0}成功", guid));
                }
                catch (Exception ex)
                {
                    //记录日志
                    logger.Error(ex);
                    //抛出异常
                    throw;
                }
            }
        }
    }

   IndexHelper 添加、更新、删除索引

    using Lucene.Net.Analysis;
    using Lucene.Net.Analysis.PanGu;
    using Lucene.Net.Documents;
    using Lucene.Net.Index;
    using Lucene.Net.Search;
    using Lucene.Net.Store;
    using Model.HelperModel;
    using System;
    using System.Collections.Generic;
   
    namespace BLL
    {
        public static class SearchBLL
        {
            //一个类中可能会有多处输出到日志，多处需要记录日志，常将logger做成static 静态变量
            /// <summary>
            /// 日志助手
            /// </summary>
            static Common.LogHelper logger = new Common.LogHelper(typeof(SearchBLL));
            /// <summary>
            /// 索引保存位置
            /// </summary>
            static string indexPath = Common.ConfigurationHelper.AppSettingMapPath("IndexPath");
            /// <summary>
            /// 搜索
            /// </summary>
            /// <param name="keywords">用户搜索的关键词</param>
            /// <returns>返回搜索的结果</returns>
            public static List<SearchResult> Search(string keywords)
            {
                try
                {
                    //索引存储库
                    FSDirectory directory = FSDirectory.Open(new System.IO.DirectoryInfo(indexPath), new NoLockFactory());
                    //创建IndexReader对象
                    IndexReader reader = IndexReader.Open(directory, true);
                    //创建IndexSearcher对象
                    IndexSearcher searcher = new IndexSearcher(reader);
                    //新建PhraseQuery 查询对象
                    PhraseQuery query = new PhraseQuery();
                    //把用户输入的关键词进行拆词
                    foreach (string word in SplitWord(keywords))
                    {
                        //添加搜索关键词
                        query.Add(new Term("body", word));
                    }
                    //设置分词间距为100字之内
                    query.SetSlop();
                    TopScoreDocCollector collector = TopScoreDocCollector.create(, true);
                    //根据查询条件查询结果
                    searcher.Search(query, null, collector);
                    //搜索到的ScoreDoc结果
                    ScoreDoc[] docs = collector.TopDocs(, collector.GetTotalHits()).scoreDocs;
                    //保存搜索结果的list
                    List<SearchResult> listResult = new List<SearchResult>();
                    for (int i = ; i < docs.Length; i++)
                    {
                        //取到文档的编号（主键，这个是Lucene .net分配的）
                        //检索结果中只有文档的id，如果要取Document，则需要Doc再去取
                        //降低内容占用
                        int docId = docs[i].doc;
                        //根据id找Document
                        Document doc = searcher.Doc(docId);
                        string number = doc.Get("id");
                        string title = doc.Get("title");
                        string body = doc.Get("body");
                        string url = doc.Get("url");
                        //建立一个搜索结果对象
                        SearchResult result = new SearchResult();
                        result.Number = number;
                        result.Title = title;
                        result.BodyPreview = Preview(body, keywords);
                        result.Url = url;
                        //添加到结果列表
                        listResult.Add(result);
                    }
                    if (listResult.Count == )
                    {
                        return null;
                    }
                    else
                    {
                        return listResult;
                    }
                }
                catch (SystemException ex)
                {
                    logger.Error(ex);
                    return null;
                }
                catch (Exception ex)
                {
                    logger.Error(ex);
                    return null;
                }
            }
   
            /// <summary>
            /// 获取内容预览
            /// </summary>
            /// <param name="body">内容</param>
            /// <param name="keyword">关键词</param>
            /// <returns></returns>
            private static string Preview(string body, string keyword)
            {
                //创建HTMLFormatter,参数为高亮单词的前后缀
                PanGu.HighLight.SimpleHTMLFormatter simpleHTMLFormatter = new PanGu.HighLight.SimpleHTMLFormatter("<font color=\"red\">", "</font>");
                //创建 Highlighter ，输入HTMLFormatter 和 盘古分词对象Semgent
                PanGu.HighLight.Highlighter highlighter = new PanGu.HighLight.Highlighter(simpleHTMLFormatter, new PanGu.Segment());
                //设置每个摘要段的字符数
                highlighter.FragmentSize = ;
                //获取最匹配的摘要段
                string bodyPreview = highlighter.GetBestFragment(keyword, body);
                return bodyPreview;
            }
   
            /// <summary>
            /// 盘古分词，对用户输入的搜索关键词进行分词
            /// </summary>
            /// <param name="str">用户输入的关键词</param>
            /// <returns>分词之后的结果组成的数组</returns>
            private static string[] SplitWord(string str)
            {
                List<string> list = new List<string>();
                Analyzer analyzer = new PanGuAnalyzer();
                TokenStream tokenStream = analyzer.TokenStream("", new System.IO.StringReader(str));
                Lucene.Net.Analysis.Token token = null;
                while ((token = tokenStream.Next()) != null)
                {
                    list.Add(token.TermText());
                }
                return list.ToArray();
            }
        }
    }

   Search 通过查找索引实现搜索

    namespace Model.HelperModel
    {
        public class SearchResult
        {
            public string Number { get; set; }
   
            public string Title { get; set; }
   
            public string BodyPreview { get; set; }
   
            public string Url { get; set; }
        }
    }

   SearchResult 模型