Encapsulate the Connection-related Operations That Every JDBC Program Seems to Use

package com.darwinsys;
 
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002.
 * All rights reserved. Software written by Ian F. Darwin and others.
 * $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee
 * cup" logo are trademarks of Sun Microsystems. Sun's, and James Gosling's,
 * pioneering role in inventing and promulgating (and standardizing) the Java 
 * language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
 * inventing predecessor languages C and C++ is also gratefully acknowledged.
 */
 
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
 
/**
 * Encapsulate the Connection-related operations that every JDBC program seems
 * to use.
 */
public class ConnectionUtil {
    /** The default config filename, relative to ${user.home} */
    public static final String DEFAULT_NAME = ".db.properties";
 
    /** The current config filename */
    private static String configFileName = System.getProperty("user.home")
	    + File.separator + DEFAULT_NAME;
 
    /**
     * Get a Connection for the given config using the default or set property
     * file name
     */
    public static Connection getConnection(String config) throws Exception {
	try {
	    Properties p = new Properties();
	    p.load(new FileInputStream(configFileName));
	    return getConnection(p, config);
	} catch (IOException ex) {
	    throw new Exception(ex.toString());
	}
    }
 
    /** Get a Connection for the given config name from a provided Properties */
    public static Connection getConnection(Properties p, String config)
	    throws Exception {
	try {
	    String db_driver = p.getProperty(config + "." + "DBDriver");
	    String db_url = p.getProperty(config + "." + "DBURL");
	    String db_user = p.getProperty(config + "." + "DBUser");
	    String db_password = p.getProperty(config + "." + "DBPassword");
	    if (db_driver == null || db_url == null) {
		throw new IllegalStateException("Driver or URL null: " + config);
	    }
	    return createConnection(db_driver, db_url, db_user, db_password);
	} catch (ClassNotFoundException ex) {
	    throw new Exception(ex.toString());
 
	} catch (SQLException ex) {
	    throw new Exception(ex.toString());
	}
    }
 
    public static Connection createConnection(String db_driver, String db_url,
	    String db_user, String db_password) throws ClassNotFoundException,
	    SQLException {
 
	// Load the database driver
	System.out.println("Loading driver " + db_driver);
	Class.forName(db_driver);
 
	System.out.println("Connecting to DB " + db_url);
	return DriverManager.getConnection(db_url, db_user, db_password);
    }
 
    /**
     * Returns the full path of the configuration file being used.
     * 
     * @return Returns the configFileName.
     */
    public static String getConfigFileName() {
	return configFileName;
    }
 
    /**
     * Sets the full path of the config file to read.
     * 
     * @param configFileNam
     *            The FileName of the configuration file to use.
     */
    public static void setConfigFileName(String configFileNam) {
	configFileName = configFileNam;
	File file = new File(configFileName);
	if (!file.canRead()) {
	    throw new IllegalArgumentException("Unreadable: " + configFileName);
	}
	try {
	    ConnectionUtil.configFileName = file.getCanonicalPath();
	} catch (IOException ex) {
	    System.err.println("Warning: IO error checking path: "
		    + configFileName);
	    ConnectionUtil.configFileName = configFileName;
	}
    }
}