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;
               }
           }
       }
   }

   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(100);
                   TopScoreDocCollector collector = TopScoreDocCollector.create(1000, 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(0, collector.GetTotalHits()).scoreDocs;
                   //保存搜索结果的list
                   List<SearchResult> listResult = new List<SearchResult>();
                   for (int i = 0; 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 == 0)
                   {
                       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 = 100;
               //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();
           }
       }
   }

   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; }
       }
   }