jforum example source code file (DBConnection.java)

This example jforum source code file (DBConnection.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - jforum tags/keywords

connection, connection, dbconnection, dbconnection, error, error, exception, exception, jdbc, logger, sql

The jforum DBConnection.java source code

/*
 * Copyright (c) JForum Team
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, 
 * with or without modification, are permitted provided 
 * that the following conditions are met:
 * 
 * 1) Redistributions of source code must retain the above 
 * copyright notice, this list of conditions and the 
 * following  disclaimer.
 * 2)  Redistributions in binary form must reproduce the 
 * above copyright notice, this list of conditions and 
 * the following disclaimer in the documentation and/or 
 * other materials provided with the distribution.
 * 3) Neither the name of "Rafael Steil" nor 
 * the names of its contributors may be used to endorse 
 * or promote products derived from this software without 
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT 
 * HOLDERS AND CONTRIBUTORS "AS IS" AND ANY 
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, 
 * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR 
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL 
 * THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE 
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, 
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES 
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER 
 * IN CONTRACT, STRICT LIABILITY, OR TORT 
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF 
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE
 * 
 * This file creation date: 25/08/2004 23:03:14
 * The JForum Project
 * http://www.jforum.net
 */
package net.jforum;

import java.sql.Connection;

import net.jforum.util.preferences.ConfigKeys;
import net.jforum.util.preferences.SystemGlobals;

import org.apache.log4j.Logger;

/**
 * Base class for all database connection implementations that
 * may be used with JForum.
 * Default implementations are <code>PooledConnection, which
 * is the defeault connection pool implementation, and <code>SimpleConnection,
 * which opens a new connection on every request.  
 * 
 * @author Rafael Steil
 * @version $Id: DBConnection.java,v 1.14 2006/08/23 02:24:06 rafaelsteil Exp $
 */
public abstract class DBConnection 
{
	private static final Logger logger = Logger.getLogger(DBConnection.class);
	protected boolean isDatabaseUp;
	
	private static DBConnection instance;

	/**
	 * Creates an instance of some <code>DBConnection implementation. 
	 * 
	 * @return <code>true if the instance was successfully created, 
	 * or <code>false if some exception was thrown.
	 */
	public static boolean createInstance()
	{
		try {
			instance = (DBConnection)Class.forName(SystemGlobals.getValue(
					ConfigKeys.DATABASE_CONNECTION_IMPLEMENTATION)).newInstance();
		}
		catch (Exception e) {
			 logger.warn("Error creating the database connection implementation instance. " + e);
			 e.printStackTrace();
			 return false;
		}
		
		return true;
	}
	
	/**
	 * Gets the current <code>DBConnection implementation's instance
	 * 
	 * @return DBConnection
	 */
	public static DBConnection getImplementation()
	{
		return instance;
	}
	
	/**
	 * Checks if database connection is up.
	 *  
	 * @return <code>true if a connection to the database
	 * was successfully created, or <code>false if not.
	 */
	public boolean isDatabaseUp()
	{
		return this.isDatabaseUp;
	}
	
	/**
	 * Inits the implementation. 
	 * Connection pools may use this method to init the connections from the
	 * database, while non-pooled implementation can provide an empty method
	 * block if no other initialization is necessary.
	 * <br>
	 * Please note that this method will be called just once, at system startup. 
	 * 
	 * @throws Exception
	 */
	public abstract void init() throws Exception;
	
	/**
	 * Gets a connection.
	 * Connection pools' normal behaviour will be to once connection
	 * from the pool, while non-pooled implementations will want to
	 * go to the database and get the connection in time the method
	 * is called.
	 * 
	 * @return Connection
	 */
	public abstract Connection getConnection();
	
	/**
	 * Releases a connection.
	 * Connection pools will want to put the connection back to the pool list,
	 * while non-pooled implementations should call <code>close() directly
	 * in the connection object.
	 * 
	 * @param conn The connection to release
	 */
	public abstract void releaseConnection(Connection conn);
	
	/**
	 * Close all open connections.
	 * 
	 * @throws Exception
	 */
	public abstract void realReleaseAllConnections() throws Exception;
}