Hibernate Search + Apache Lucene (tricks)

In this post I would like to show a few Hibernate Search tricks which could be useful in some cases (at least, I use them quite often):

• how to get all indexed properties for entity?

final Class< ? > entityClass = ...;

final FullTextSession fullTextSession = Search.getFullTextSession(
sessionFactory.getCurrentSession() );

final SearchFactory searchFactory = fullTextSession.getSearchFactory();
final ReaderProvider readerProvider = searchFactory.getReaderProvider();

final Collection< String > names = new ArrayList< String >();
IndexReader indexReader = null;

try {
 indexReader = readerProvider.openReader( searchFactory.getDirectoryProviders( clazz ) );
 for( Object obj: indexReader.getFieldNames( FieldOption.INDEXED ) ) {
     if( obj instanceof String ) {
         String name = ( String )obj;   
         names.add( name );
     }
 }
} finally {
 if( indexReader != null ) {
     readerProvider.closeReader( indexReader );
 }
}

• how to reindex whole existing database?

final FullTextSession fullTextSession = Search.getFullTextSession(
 sessionFactory.getCurrentSession() );

final Set< ? > entitites = new HashSet< ? >();
// Get all indexed persistent entities from Hibernate session factory
Iterator< ? > iterator = sessionFactory.getConfiguration().getClassMappings();
while( iterator.hasNext() ) {
 Object obj = iterator.next();
 if( obj instanceof PersistentClass ) {
     PersistentClass persistentClass = ( PersistentClass )obj;
     try {
         Class< ? > clazz = Class.forName( persistentClass.getClassName() );
         if( clazz.getAnnotation( Indexed.class ) != null ) {
           entitites.add( clazz );
         }
     }
 } catch( ClassNotFoundException ex ) {
     ex.printStackTrace();
 }
}

for( Class< ? > entityClass: entitites ) {
 fullTextSession.purgeAll( entityClass );
 fullTextSession.flushToIndexes();

 for( Object entity: session.createCriteria( entityClass ).list() ) {
     fullTextSession.index( entity );  
 }
}

fullTextSession.flushToIndexes();
fullTextSession.getSearchFactory().optimize();