Lucene - WildcardQuery

WildcardQuery is used to search documents using wildcards like '*' for any character sequence, matching a single character.
Following is the declaration for org.apache.lucene.search.WildcardQuery class −
public class WildcardQuery 
   extends MultiTermQuery 

protected Term term
WildcardQuery(Term term)
boolean equals(Object obj)
protected FilteredTermEnum getEnum(IndexReader reader)
Construct the enumeration to be used, expanding the pattern term.
Term getTerm()
Returns the pattern term.
int hashCode()
String toString(String field)
Prints a user-readable version of this query.
This class inherits methods from the following classes −
org.apache.lucene.search.MultiTermQuery
org.apache.lucene.search.Query
java.lang.Object
private void searchUsingWildCardQuery(String searchQuery) 
   throws IOException, ParseException { 
   searcher = new Searcher(indexDir); 
   long startTime = System.currentTimeMillis(); 
	
   //create a term to search file name 
   Term term = new Term(LuceneConstants.FILE_NAME, searchQuery); 
   //create the term query object 
   Query query = new WildcardQuery(term); 
   //do the search 
   TopDocs hits = searcher.search(query); 
   long endTime = System.currentTimeMillis();  
	
   System.out.println(hits.totalHits + 
      " documents found. Time :" + (endTime - startTime) + "ms"); 
		
   for(ScoreDoc scoreDoc : hits.scoreDocs) { 
      Document doc = searcher.getDocument(scoreDoc); 
      System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH)); 
   } 
	
   searcher.close(); 
} 
Let us create a test Lucene application to test search using WildcardQuery.
Create a project with a name LuceneFirstApplication under a package com.tutorialspoint.lucene as explained in the Lucene - First Application chapter. You can also use the project created in Lucene - First Application chapter as such for this chapter to understand the searching process.
Create LuceneConstants.java and Searcher.java as explained in the Lucene - First Application chapter. Keep the rest of the files unchanged.
Create LuceneTester.java as mentioned below.
Clean and Build the application to make sure the business logic is working as per the requirements.
This class is used to provide various constants to be used across the sample application.
package com.tutorialspoint.lucene;  
public class LuceneConstants { 
   public static final String CONTENTS = "contents"; 
   public static final String FILE_NAME = "filename"; 
   public static final String FILE_PATH = "filepath"; 
   public static final int MAX_SEARCH = 10; 
}
This class is used to read the indexes made on raw data and searches data using lucene library.
package com.tutorialspoint.lucene;  

import java.io.File; 
import java.io.IOException;  

import org.apache.lucene.analysis.standard.StandardAnalyzer; 
import org.apache.lucene.document.Document; 
import org.apache.lucene.index.CorruptIndexException; 
import org.apache.lucene.queryParser.ParseException; 
import org.apache.lucene.queryParser.QueryParser; 

import org.apache.lucene.search.IndexSearcher; 
import org.apache.lucene.search.Query; 
import org.apache.lucene.search.ScoreDoc; 
import org.apache.lucene.search.TopDocs; 

import org.apache.lucene.store.Directory; 
import org.apache.lucene.store.FSDirectory; 

import org.apache.lucene.util.Version; 
 
public class Searcher { 
  
   IndexSearcher indexSearcher; 
   QueryParser queryParser; 
   Query query;  
	
   public Searcher(String indexDirectoryPath) throws IOException { 
      Directory indexDirectory =  FSDirectory.open(new File(indexDirectoryPath)); 
      indexSearcher = new IndexSearcher(indexDirectory); 
      queryParser = new QueryParser(Version.LUCENE_36, LuceneConstants.CONTENTS, 
         new StandardAnalyzer(Version.LUCENE_36)); 
   } 
	
   public TopDocs search( String searchQuery) throws IOException, ParseException { 
      query = queryParser.parse(searchQuery); 
      return indexSearcher.search(query, LuceneConstants.MAX_SEARCH); 
   } 
    
   public TopDocs search(Query query) throws IOException, ParseException { 
      return indexSearcher.search(query, LuceneConstants.MAX_SEARCH); 
   } 
	
   public Document getDocument(ScoreDoc scoreDoc) 
      throws CorruptIndexException, IOException { 
      return indexSearcher.doc(scoreDoc.doc);  
   }
	
   public void close() throws IOException { 
      indexSearcher.close(); 
   } 
}
This class is used to test the searching capability of lucene library.
package com.tutorialspoint.lucene;
  
import java.io.IOException;  

import org.apache.lucene.document.Document; 
import org.apache.lucene.index.Term; 
import org.apache.lucene.queryParser.ParseException; 
import org.apache.lucene.search.WildcardQuery; 

import org.apache.lucene.search.Query; 
import org.apache.lucene.search.ScoreDoc; 
import org.apache.lucene.search.TopDocs; 
 
public class LuceneTester { 
  
   String indexDir = "E:\\Lucene\\Index"; 
   String dataDir = "E:\\Lucene\\Data"; 
   Searcher searcher; 
	
   public static void main(String[] args) { 
      LuceneTester tester; 
      try { 
         tester = new LuceneTester(); 
         tester.searchUsingWildCardQuery("record1*"); 
      } catch (IOException e) { 
         e.printStackTrace(); 
      } catch (ParseException e) { 
         e.printStackTrace(); 
      } 
   } 
	
   private void searchUsingWildCardQuery(String searchQuery) 
      throws IOException, ParseException { 
      searcher = new Searcher(indexDir); 
      long startTime = System.currentTimeMillis(); 
		
      //create a term to search file name 
      Term term = new Term(LuceneConstants.FILE_NAME, searchQuery); 
      //create the term query object 
      Query query = new WildcardQuery(term); 
      //do the search 
      TopDocs hits = searcher.search(query); 
      long endTime = System.currentTimeMillis(); 
		
      System.out.println(hits.totalHits + 
         " documents found. Time :" + (endTime - startTime) + "ms"); 
			
      for(ScoreDoc scoreDoc : hits.scoreDocs) { 
         Document doc = searcher.getDocument(scoreDoc); 
         System.out.println("File: "+ doc.get(LuceneConstants.FILE_PATH)); 
      } 
		
      searcher.close(); 
   } 
} 
I've used 10 text files named from record1.txt to record10.txt containing simply names and other details of the students and put them in the directory E:\Lucene\Data. Test Data. An index directory path should be created as E:\Lucene\Index. After running the indexing program during chapter Lucene - Indexing Process, you can see the list of index files created in that folder.
Once you are done with creating source, creating the raw data, data directory, index directory and indexes, you are ready for this step which is compiling and running your program. To do this, Keep LuceneTester.Java file tab active and use either Run option available in the Eclipse IDE or use Ctrl + F11 to compile and run your LuceneTester application. If everything is fine with your application, this will print the following message in Eclipse IDE's console −
2 documents found. Time :47ms 
File: E:\Lucene\Data\record1.txt 
File: E:\Lucene\Data\record10.txt

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