使用Lucene.NET实现站内搜索

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

创建索引、更新索引、删除索引

搜索，根据索引查找

IndexHelper 添加、更新、删除索引

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;
      }
    }
  }
}

Search 通过查找索引实现搜索

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();
    }
  }
}

SearchResult 模型

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; }
  }
}

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