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Lightweight connection pool.
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/**
 *  Copyright 2010 Wallace Wadge
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

package com.jolbox.bonecp;

import java.io.Serializable;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Parent class for the different pool strategies.
 * @author wallacew
 *
 */
public abstract class AbstractConnectionStrategy implements ConnectionStrategy,Serializable{

	/**
	 * uuid
	 */
	private static final long serialVersionUID = 27805973487155497L;

	/** Pool handle */
	protected BoneCP pool;
	
	/** Prevent repeated termination of all connections when the DB goes down. */
	protected Lock terminationLock = new ReentrantLock();
	
	
	/** Prep for a new connection
	 * @return if stats are enabled, return the nanoTime when this connection was requested.
	 * @throws SQLException
	 */
	protected long preConnection() throws SQLException{
		long statsObtainTime = 0;
		
		if (this.pool.poolShuttingDown){
			throw new SQLException(this.pool.shutdownStackTrace);
		}


		if (this.pool.statisticsEnabled){
			statsObtainTime = System.nanoTime();
			this.pool.statistics.incrementConnectionsRequested();
		}
		
		return statsObtainTime;
	}
	
	
	/** After obtaining a connection, perform additional tasks.
	 * @param handle
	 * @param statsObtainTime
	 */
	protected void postConnection(ConnectionHandle handle, long statsObtainTime){

		handle.renewConnection(); // mark it as being logically "open"

		// Give an application a chance to do something with it.
		if (handle.getConnectionHook() != null){
			handle.getConnectionHook().onCheckOut(handle);
		}

		if (this.pool.closeConnectionWatch){ // a debugging tool
			this.pool.watchConnection(handle);
		}

		if (this.pool.statisticsEnabled){
			this.pool.statistics.addCumulativeConnectionWaitTime(System.nanoTime()-statsObtainTime);
		}
	}

	public Connection getConnection() throws SQLException {
		long statsObtainTime = preConnection();
		
		ConnectionHandle result = (ConnectionHandle) getConnectionInternal();
		if (result != null){
			postConnection(result, statsObtainTime);
		}
		
		return result;
	}

	/** Actual call that returns a connection
	 * @return Connection
	 * @throws SQLException
	 */
	protected abstract Connection getConnectionInternal() throws SQLException;
	
		
	public ConnectionHandle pollConnection(){
		// usually overridden
		return null; 
	}
	
	/* (non-Javadoc)
	 * @see com.jolbox.bonecp.ConnectionStrategy#cleanupConnection(com.jolbox.bonecp.ConnectionHandle)
	 */
	public void cleanupConnection(ConnectionHandle oldHandle,
			ConnectionHandle newHandle) {
		// do nothing
	}
	
}