NHibernate.Search 整合 Lucene.NET 實現全文檢索完整教學

專案簡介

NHibernate.Search 是 NHibernate Contrib 專案，移植自 Hibernate Search，將 NHibernate ORM 與 Lucene.NET 全文搜尋引擎無縫整合：資料持久化到資料庫，索引與查詢交給 Lucene.NET。

一、組態設定

1. 新增設定區段

<configSections>
  <section name="hibernate-configuration" type="NHibernate.Cfg.ConfigurationSectionHandler, NHibernate"/>
  <section name="nhs-configuration" type="NHibernate.Search.Cfg.ConfigurationSectionHandler, NHibernate.Search" requirePermission="false"/>
</configSections>

2. NHibernate 核心設定（以 SQLite 為例）

<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
  <session-factory name="NHibernateSearch.Demo">
    <property name="connection.driver_class">NHibernate.Driver.SQLite20Driver</property>
    <property name="connection.connection_string">Data Source=|DataDirectory|Demo.db3;Version=3;</property>
    <property name="dialect">NHibernate.Dialect.SQLiteDialect</property>
    <property name="show_sql">true</property>
    <mapping assembly="NHibernateSearch.Demo.Model"/>
  </session-factory>
</hibernate-configuration>

3. NHibernate.Search 索引設定

<nhs-configuration xmlns='urn:nhs-configuration-1.0'>
  <search-factory sessionFactoryName="NHibernateSearch.Demo">
    <property name='hibernate.search.default.directory_provider'>NHibernate.Search.Store.FSDirectoryProvider, NHibernate.Search</property>
    <property name='hibernate.search.default.indexBase'>~/Index</property>
    <property name='hibernate.search.default.indexBase.create'>true</property>
  </search-factory>
</nhs-configuration>

索引檔案將存放在專案根目錄下的 Index 資料夾。

4. 事件監聽器：自動同步索引

需在程式碼中手動註冊（目前不支援純組態）：

Configuration cfg = new Configuration();
cfg.SetListener(ListenerType.PostInsert, new FullTextIndexEventListener());
cfg.SetListener(ListenerType.PostUpdate, new FullTextIndexEventListener());
cfg.SetListener(ListenerType.PostDelete, new FullTextIndexEventListener());
cfg.Configure();
sessionFactory = cfg.BuildSessionFactory();

新增、修改、刪除實體時，索引將自動更新，支援批次提交以優化效能。

二、實體類別標記索引屬性

[Indexed(Index = "Book")]
public class Book
{
    [DocumentId]
    public virtual string BookID { get; set; }

    [Field(Index.Tokenized, Store = Store.Yes)]
    public virtual string Title { get; set; }

    [Field(Index.Tokenized, Store = Store.Yes)]
    public virtual string Authors { get; set; }

    [Field(Index.Tokenized, Store = Store.Yes)]
    public virtual string Publisher { get; set; }

    [Field(Index.Tokenized, Store = Store.Yes)]
    public virtual string Summary { get; set; }
}

屬性標記即完成索引定義，CRUD 操作自動觸發索引維護。

三、全文搜尋與關鍵字高亮實作

public static IList<BookSearchResult> FindBooks(string query)
{
    var results = new List<BookSearchResult>();
    var analyzer = new StandardAnalyzer();
    var parser = new MultiFieldQueryParser(new[] { "Title", "Summary", "Authors", "Publisher" }, analyzer);
    Query luceneQuery;
    try { luceneQuery = parser.Parse(query); }
    catch (ParseException) { return results; }

    IFullTextSession fts = Search.CreateFullTextSession(NHibernateHelper.GetCurrentSession());
    var books = fts.CreateFullTextQuery(luceneQuery, typeof(Book)).List<Book>();

    // 高亮器建立
    var formatter = new SimpleHTMLFormatter("<b class='term'>", "</b>");
    var highlighter = new Highlighter(formatter);

    foreach (var book in books)
    {
        var result = new BookSearchResult(book);
        result.HighlightedTitle = highlighter.GetBestFragment(analyzer, "Title", book.Title);
        result.HighlightedSummary = highlighter.GetBestFragments(analyzer, "Summary", book.Summary, 3, "...<br/><br/>...");
        // ... 其他欄位同理
        results.Add(result);
    }
    return results;
}

關鍵點：

• 使用 IFullTextSession 執行全文查詢。
• MultiFieldQueryParser 支援多欄位同時搜尋。
• Highlighter 配合 SimpleHTMLFormatter 實現關鍵字高亮。

四、執行結果展示

輸入關鍵字「程式」即時顯示符合記錄，關鍵字以粗體標示，效能遠優於資料庫 LIKE 查詢。

五、參考資源

1. NHibernate.Search using Lucene.NET Full Text Index Part1
2. NHibernate Search
3. Lucene.NET and NHibernate.Search on medium trust
4. Using NHibernate.Search with ActiveRecord