/*
* HA-JDBC: High-Availability JDBC
* Copyright (C) 2012 Paul Ferraro
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package net.sf.hajdbc.cache.lazy;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.SQLException;
import java.util.AbstractMap;
import java.util.Map;
import net.sf.hajdbc.Database;
import net.sf.hajdbc.DatabaseCluster;
import net.sf.hajdbc.DatabaseProperties;
import net.sf.hajdbc.cache.DatabaseMetaDataCache;
import net.sf.hajdbc.dialect.Dialect;
/**
* DatabaseMetaDataCache implementation that lazily caches data when requested.
* Used when a compromise between memory usage and performance is desired.
* Caches DatabaseProperties using a soft reference to prevent <code>OutOfMemoryError</code>s.
*
* @author Paul Ferraro
* @since 2.0
*/
public class SharedLazyDatabaseMetaDataCache<Z, D extends Database<Z>> implements DatabaseMetaDataCache<Z, D>
{
private final DatabaseCluster<Z, D> cluster;
private volatile Reference<Map.Entry<DatabaseProperties, LazyDatabaseMetaDataProvider>> entryRef = new SoftReference<Map.Entry<DatabaseProperties, LazyDatabaseMetaDataProvider>>(null);
public SharedLazyDatabaseMetaDataCache(DatabaseCluster<Z, D> cluster)
{
this.cluster = cluster;
}
/**
* @see net.sf.hajdbc.cache.DatabaseMetaDataCache#flush()
*/
@Override
public synchronized void flush()
{
this.entryRef.clear();
}
/**
* {@inheritDoc}
* @see net.sf.hajdbc.cache.DatabaseMetaDataCache#getDatabaseProperties(net.sf.hajdbc.Database, java.sql.Connection)
*/
@Override
public DatabaseProperties getDatabaseProperties(D database, Connection connection) throws SQLException
{
Map.Entry<DatabaseProperties, LazyDatabaseMetaDataProvider> entry = this.entryRef.get();
if (entry == null)
{
DatabaseMetaData metaData = connection.getMetaData();
Dialect dialect = this.cluster.getDialect();
LazyDatabaseMetaDataProvider provider = new LazyDatabaseMetaDataProvider(metaData);
DatabaseProperties properties = new LazyDatabaseProperties(provider, dialect);
entry = new AbstractMap.SimpleImmutableEntry<DatabaseProperties, LazyDatabaseMetaDataProvider>(properties, provider);
this.entryRef = new SoftReference<Map.Entry<DatabaseProperties, LazyDatabaseMetaDataProvider>>(entry);
}
else
{
entry.getValue().setConnection(connection);
}
return entry.getKey();
}
}