Use Lucene. NET for intra-Site Search

Use Lucene. NET for intra-Site Search

When it comes to Lucene, you may have heard of it. It was already an open-source technology that emerged several years ago. Many websites use it to set up intra-site searches for their websites. Recently, I have also learned how to use e.net in data retrieval.

Import Lucene. NET Development Kit

Lucene is an open-source full-text search engine toolkit of the apache Software Foundation. It is a full-text search engine architecture that provides a complete query engine and index engine, part of the text analysis engine. Lucene aims to provide software developers with a simple and easy-to-use toolkit to conveniently implement full-text retrieval in the target system, or build a complete full-text retrieval engine based on this. Lucene. Net is a. NET version of Lucene.

You can download the latest Lucene. NET

Create, update, and delete Indexes

Search, search by index

IndexHelper add, update, and delete Indexes

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Using System; Using Lucene. Net. Store; Using Lucene. Net. Index; Using Lucene. Net. Analysis. PanGu; Using Lucene. Net. Documents;   Namespace BLL { Class IndexHelper { /// <Summary> /// Log Assistant /// </Summary> Static Common. LogHelper logger = new Common. LogHelper (typeof (SearchBLL )); /// <Summary> /// Index storage location, which is saved in the configuration file and read from the configuration file /// </Summary> Static string indexPath = Common. ConfigurationHelper. deleettingmappath ("IndexPath ");   /// <Summary> /// Create an index file or update an index file /// </Summary> /// <Param name = "item"> index information </param> Public static void CreateIndex (Model. HelperModel. IndexFileHelper item) { Try { // Index Repository FSDirectory directory = FSDirectory. Open (new System. IO. DirectoryInfo (indexPath), new NativeFSLockFactory ()); // Determine whether the index exists Bool isUpdate = IndexReader. IndexExists (directory ); If (isUpdate) { // If the index directory is locked (for example, the program unexpectedly exits during the indexing process), unlock the directory first. If (IndexWriter. IsLocked (directory )) { // Unlock the index Library IndexWriter. Unlock (directory ); } } // Create an IndexWriter object and add an index IndexWriter writer = new IndexWriter (directory, new PanGuAnalyzer (),! IsUpdate, Lucene. Net. Index. IndexWriter. MaxFieldLength. UNLIMITED ); // Obtain the news title String title = item. FileTitle; // Obtain the news subject content String body = item. FileContent; // To avoid repeated indexes, delete the number = I record and add it again. // Especially for updates, you must delete the previous index first. Writer. DeleteDocuments (new Term ("id", item. FileName )); // Create an index file Document Document document = new Document (); // ANALYZED is only available for fields that require full-text search. // Add the id field Document. Add (new Field ("id", item. FileName, Field. Store. YES, Field. Index. NOT_ANALYZED )); // Add the title Field Document. Add (new Field ("title", title, Field. Store. YES, Field. Index. NOT_ANALYZED )); // Add the body Field Document. Add (new Field ("body", body, Field. Store. YES, Field. Index. ANALYZED, Lucene. Net. Documents. Field. TermVector. WITH_POSITIONS_OFFSETS )); // Add a url Field Document. Add (new Field ("url", item. FilePath, Field. Store. YES, Field. Index. NOT_ANALYZED )); // Write to the index database Writer. AddDocument (document ); // Close the resource Writer. Close (); // Do not forget to Close, otherwise the index results cannot be found Directory. Close (); // Record logs Logger. Debug (String. Format ("index {0} created", item. FileName )); } Catch (SystemException ex) { // Record error logs Logger. Error (ex ); Throw; } Catch (Exception ex) { // Record error logs Logger. Error (ex ); Throw; } }   /// <Summary> /// Delete the corresponding index based on the id /// </Summary> /// <Param name = "guid"> id of the index to be deleted </param> Public static void DeleteIndex (string guid) { Try { //// Index Repository FSDirectory directory = FSDirectory. Open (new System. IO. DirectoryInfo (indexPath), new NativeFSLockFactory ()); // Determine whether an index exists in the index database Bool isUpdate = IndexReader. IndexExists (directory ); If (isUpdate) { // If the index directory is locked (for example, the program unexpectedly exits during the indexing process), unlock the directory first. If (IndexWriter. IsLocked (directory )) { IndexWriter. Unlock (directory ); } } IndexWriter writer = new IndexWriter (directory, new PanGuAnalyzer (),! IsUpdate, Lucene. Net. Index. IndexWriter. MaxFieldLength. UNLIMITED ); // Delete the index file Writer. DeleteDocuments (new Term ("id", guid )); Writer. Close (); Directory. Close (); // do not forget to Close; otherwise, the index results cannot be found. Logger. Debug (String. Format ("index deleted {0} succeeded", guid )); } Catch (Exception ex) { // Record logs Logger. Error (ex ); // Throw an exception Throw; } } } }

Search by searching Indexes

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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 { // A class may be output to logs in multiple places. Logs need to be recorded in multiple places. logger is often made into static variables. /// <Summary> /// Log Assistant /// </Summary> Static Common. LogHelper logger = new Common. LogHelper (typeof (SearchBLL )); /// <Summary> /// Index storage location /// </Summary> Static string indexPath = Common. ConfigurationHelper. deleettingmappath ("IndexPath "); /// <Summary> /// Search /// </Summary> /// <Param name = "keywords"> keywords searched by users </param> /// <Returns> returns the search result </returns> Public static List <SearchResult> Search (string keywords) { Try { // Index Repository FSDirectory directory = FSDirectory. Open (new System. IO. DirectoryInfo (indexPath), new NoLockFactory ()); // Create an IndexReader object IndexReader reader = IndexReader. Open (directory, true ); // Create an IndexSearcher object IndexSearcher searcher = new IndexSearcher (reader ); // Create a PhraseQuery query object PhraseQuery query = new PhraseQuery (); // Split the keywords entered by the user Foreach (string word in SplitWord (keywords )) { // Add a search keyword Query. Add (new Term ("body", word )); } // Set the word segmentation interval to within 100 words Query. SetSlop (100 ); TopScoreDocCollector collector = TopScoreDocCollector. create (1000, true ); // Query results based on query Conditions Searcher. Search (query, null, collector ); // ScoreDoc result ScoreDoc [] docs = collector. TopDocs (0, collector. GetTotalHits (). scoreDocs; // Save the list of search results List <SearchResult> listResult = new List <SearchResult> (); For (int I = 0; I <docs. Length; I ++) { // Obtain the document number (primary key, which is allocated by Lucene. net) // Only the Document id is found in the search result. If you want to retrieve the Document, you need the Doc to retrieve it again. // Reduce content occupation Int docId = docspolici2.16.doc; // Search for Document by id 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 "); // Create a search result object SearchResult result = new SearchResult (); Result. Number = number; Result. Title = title; Result. BodyPreview = Preview (body, keywords ); Result. Url = url; // Add to result list 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> /// Get Content preview /// </Summary> /// <Param name = "body"> content </param> /// <Param name = "keyword"> keywords </param> /// <Returns> </returns> Private static string Preview (string body, string keyword) { // Create an HTMLFormatter. The parameter is the prefix and suffix of the highlighted word. PanGu. HighLight. SimpleHTMLFormatter simpleHTMLFormatter = new PanGu. HighLight. SimpleHTMLFormatter ("<font color = \" red \ ">", "</font> "); // Create a Highlighter and input the HTMLFormatter and pangu word segmentation object Semgent PanGu. HighLight. Highlighter highlighter = new PanGu. HighLight. Highlighter (simpleHTMLFormatter, new PanGu. Segment ()); // Set the number of characters for each abstract segment Highlighter. FragmentSize = 100; // Obtain the most matched abstract segment String bodyPreview = highlighter. GetBestFragment (keyword, body ); Return bodyPreview; }   /// <Summary> /// Pangu Word Segmentation: Word Segmentation for the search keywords entered by the user /// </Summary> /// <Param name = "str"> keywords entered by the user </param> /// <Returns> An array composed of results after word segmentation </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 Model

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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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