001/* 002 * HA-JDBC: High-Availability JDBC 003 * Copyright (c) 2004-2007 Paul Ferraro 004 * 005 * This library is free software; you can redistribute it and/or modify it 006 * under the terms of the GNU Lesser General Public License as published by the 007 * Free Software Foundation; either version 2.1 of the License, or (at your 008 * option) any later version. 009 * 010 * This library is distributed in the hope that it will be useful, but WITHOUT 011 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 012 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License 013 * for more details. 014 * 015 * You should have received a copy of the GNU Lesser General Public License 016 * along with this library; if not, write to the Free Software Foundation, 017 * Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 018 * 019 * Contact: ferraro@users.sourceforge.net 020 */ 021package net.sf.hajdbc.cache; 022 023import java.lang.ref.Reference; 024import java.lang.ref.SoftReference; 025import java.sql.Connection; 026import java.sql.SQLException; 027 028import net.sf.hajdbc.DatabaseProperties; 029import net.sf.hajdbc.Dialect; 030 031 032/** 033 * DatabaseMetaDataCache implementation that lazily caches data when requested. 034 * Used when a compromise between memory usage and performance is desired. 035 * Caches DatabaseProperties using a soft reference to prevent <code>OutOfMemoryError</code>s. 036 * 037 * @author Paul Ferraro 038 * @since 2.0 039 */ 040public class LazyDatabaseMetaDataCache extends AbstractDatabaseMetaDataCache 041{ 042 private volatile Reference<LazyDatabaseProperties> propertiesRef = new SoftReference<LazyDatabaseProperties>(null); 043 044 public LazyDatabaseMetaDataCache(Dialect dialect) 045 { 046 super(dialect); 047 } 048 049 /** 050 * @see net.sf.hajdbc.DatabaseMetaDataCache#flush() 051 */ 052 @Override 053 public void flush() 054 { 055 this.propertiesRef.clear(); 056 } 057 058 /** 059 * @see net.sf.hajdbc.DatabaseMetaDataCache#getDatabaseProperties(java.sql.Connection) 060 */ 061 @Override 062 public synchronized DatabaseProperties getDatabaseProperties(Connection connection) throws SQLException 063 { 064 LazyDatabaseProperties properties = this.propertiesRef.get(); 065 066 if (properties == null) 067 { 068 properties = new LazyDatabaseProperties(connection.getMetaData(), new DatabaseMetaDataSupportFactoryImpl(), this.dialect); 069 070 this.propertiesRef = new SoftReference<LazyDatabaseProperties>(properties); 071 } 072 else 073 { 074 properties.setConnection(connection); 075 } 076 077 return properties; 078 } 079}