How to populate a lucene 5.3 index - lucene

Question

I have written the following class to populate a Lucene Index. I want to build an Index for Lucene so that I can query for specific documents. Unfortunately my documents are not added to the index.
Here is my code:
public class LuceneIndexer {
private IndexWriter indexWriter;
private IndexReader indexReader;
public LuceneIndexer() throws Exception {
Directory indexDir = FSDirectory.open(Paths.get("./index-directory"));
IndexWriterConfig config = new IndexWriterConfig(new StandardAnalyzer());
config.setCommitOnClose(true);
config.setOpenMode(OpenMode.CREATE);
this.indexWriter = new IndexWriter(indexDir, config);
indexReader = DirectoryReader.open(this.indexWriter, true);
}
public void indexRelation(String subject, String description, String object) throws IOException {
System.out.println("Indexing relation between: " + subject+" and "+object);
Document doc = new Document();
doc.add(new TextField("subject", subject, Field.Store.YES));
doc.add(new TextField("description", description, Field.Store.YES));
doc.add(new TextField("object", object, Field.Store.YES));
indexWriter.addDocument(doc);
}
public void commit() throws Exception {
indexWriter.commit();
}
public int getNumberOfRelations() {
return indexReader.numDocs();
}
}
I am trying to get the following testcase to pass:
public class LuceneIndexerTest {
private LuceneIndexer instance;
#Before
public void setUp() throws SQLException, IOException {
instance = new LuceneIndexer();
instance.indexRelation("subject1","descr1","object1");
instance.indexRelation("subject2","descr2","object2");
instance.indexRelation("subject3","descr3","object3");
instance.commit();
}
#After
public void tearDown() throws IOException {
instance.close();
}
#Test
public void testIndexing() {
Assert.assertEquals(3, instance.getNumberOfRelations());
Assert.assertEquals(3, instance.getNumberOfRelations("subject"));
}
Unfortunately the Testcase says there are 0 documents in the index.

Answer 1

From Lucene's javadoc: "Any changes made to the index via IndexWriter will not be visible until a new IndexReader is opened".
The indexReader keep a view on your index at the time the IndexReader object was created. Just create a new one after each commit, and your indexReader will work as expected.
Here is the fix for your LuceneIndexer class:
public void commit() throws Exception {
indexWriter.commit();
if (indexReader != null)
indexReader.close();
indexReader = DirectoryReader.open(this.indexWriter, true);
}