@Override
 public void close() {
   CloseUtil.close(indexSearcher);
   CloseUtil.close(indexReader);
   CloseUtil.close(indexWriter);
   CloseUtil.close(directory);
   opened.set(false);
   if (logger.isWarnEnabled()) {
     logger.warn("search engine has been closed.");
   }
 }
 public OperationResponse commitAndOptimize() {
   try {
     if (logger.isDebugEnabled()) {
       logger.debug("commiting...");
     }
     indexWriter.commit();
     if (logger.isDebugEnabled()) {
       logger.debug("commit finish.");
     }
     if (logger.isDebugEnabled()) {
       logger.debug("optimizing...");
     }
     indexWriter.forceMerge(defaultMergeSize);
     if (logger.isDebugEnabled()) {
       logger.debug("optimize finish.");
     }
     reopenSearcher();
   } catch (IOException e) {
     logger.error("optimize error", e);
     return new OperationResponse(e.getMessage(), ResultCodes.COMMON_ERROR);
   } catch (OutOfMemoryError e) {
     CloseUtil.close(indexWriter);
     logger.error("error of OOM", e);
     return new OperationResponse(e.getMessage(), ResultCodes.COMMON_ERROR);
   }
   return new OperationResponse();
 }
 protected void reopenSearcher() throws IOException {
   try {
     reopenLock.lock();
     if (updateCount.get() > 0) {
       logger.info("proccessing reopen...");
       IndexReader oldIndexReader = this.indexReader;
       IndexSearcher oldIndexSearcher = this.indexSearcher;
       IndexReader newIndexReader = IndexReader.openIfChanged(oldIndexReader);
       if (newIndexReader != null) {
         IndexSearcher newIndexSearcher = new IndexSearcher(newIndexReader);
         indexSearcher = newIndexSearcher;
         indexReader = newIndexReader;
         CloseUtil.close(oldIndexReader);
         CloseUtil.close(oldIndexSearcher);
       }
       updateCount.set(0);
       logger.info("proccess reopen finish.");
     } else {
       logger.info("no thing to reopen");
     }
   } finally {
     reopenLock.unlock();
   }
 }
 @Override
 public OperationResponse commit() {
   try {
     if (logger.isDebugEnabled()) {
       logger.debug("commiting...");
     }
     indexWriter.commit();
     if (logger.isDebugEnabled()) {
       logger.debug("commit finish.");
     }
     reopenSearcher();
   } catch (IOException e) {
     logger.error("commit error", e);
     return new OperationResponse(e.getMessage(), ResultCodes.COMMON_ERROR);
   } catch (OutOfMemoryError e) {
     CloseUtil.close(indexWriter);
     logger.error("error of OOM", e);
     // TODO reopen writer?
     return new OperationResponse(e.getMessage(), ResultCodes.COMMON_ERROR);
   }
   return new OperationResponse();
 }
  protected void open(Directory directory) throws IOException {
    IndexWriter newIndexWriter = null;
    IndexReader newIndexReader = null;
    IndexSearcher newIndexSearcher = null;
    if (logger.isDebugEnabled()) {
      logger.debug("opening directory...");
    }
    try {
      IndexWriterConfig indexWriterConfig =
          new IndexWriterConfig(LuceneConfig.LUCENE_VERSION, schema.getAnalyzer());
      newIndexWriter = new IndexWriter(directory, indexWriterConfig);
      newIndexReader = IndexReader.open(newIndexWriter, true);
      newIndexSearcher = new IndexSearcher(newIndexReader);

      synchronized (this) {
        IndexWriter oldIndexWriter = this.indexWriter;
        IndexSearcher oldIndexSearcher = this.indexSearcher;
        IndexReader oldIndexReader = this.indexReader;

        this.indexWriter = newIndexWriter;
        this.indexSearcher = newIndexSearcher;
        this.indexReader = newIndexReader;

        CloseUtil.close(oldIndexSearcher);
        CloseUtil.close(oldIndexReader);
        CloseUtil.close(oldIndexWriter);
      }
      if (logger.isDebugEnabled()) {
        logger.debug("open directory finish.");
      }
    } catch (IOException e) {
      logger.error("open directory error", e);
      CloseUtil.close(newIndexSearcher);
      CloseUtil.close(newIndexReader);
      CloseUtil.close(newIndexWriter);
      throw e;
    }
  }