Metacat

    // a hash table serves as query reuslt cache. Key of hashtable

    // is a query string and value is ResultDocumentSet Object

    private static Hashtable queryResultCache = new Hashtable();

    // Capacity of the query result cache

    private static final int QUERYRESULTCACHESIZE = Integer.parseInt(MetaCatUtil.getOption("queryresult_cache_size"));

   /*

    * Method to store query string and DocumentResultSet into query result

    * cache. If the size alreay reache the limitation, the cache will be

    * cleared first, then store them.

    */

   private void storeQueryResultIntoCache(String query, ResultDocumentSet resultSet)

   {

	   synchronized (queryResultCache)

	   {

		   if (queryResultCache.size() >= QUERYRESULTCACHESIZE)

		   {

			   queryResultCache.clear();

		   }

		   queryResultCache.put(query, resultSet);

	   }

   }

   /*

    * Method to get DocumentResultSet from query result cache. 

    * Note: the returned ResultDoucmentSet can be null.

    */

   private ResultDocumentSet getResultDocumentSetFromCache(String query)

   {

	   ResultDocumentSet resultSet = null;

	   synchronized (queryResultCache)

	   {

          try

          {

		     resultSet = (ResultDocumentSet)queryResultCache.get(query);

          }

          catch (Exception e)

          {

        	  resultSet = null;

          }

	   }

	   return resultSet;

   }

   /**

    * Method to clear the query result cache.

    */

   public static void clearQueryResultCache()

   {

	   synchronized (queryResultCache)

	   {

		   queryResultCache.clear();

	   }

   }