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			347 lines
		
	
	
		
			9.9 KiB
		
	
	
	
		
			Java
		
	
	
	
			
		
		
	
	
			347 lines
		
	
	
		
			9.9 KiB
		
	
	
	
		
			Java
		
	
	
	
/* DriverManager.java -- Manage JDBC drivers
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   Copyright (C) 1999, 2000, 2001, 2003 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING.  If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library.  Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module.  An independent module is a module which is not derived from
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or based on this library.  If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so.  If you do not wish to do so, delete this
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exception statement from your version. */
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package java.sql;
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import java.io.PrintStream;
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import java.io.PrintWriter;
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import java.util.Enumeration;
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import java.util.Properties;
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import java.util.Vector;
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import java.util.StringTokenizer;
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/**
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  * This class manages the JDBC drivers in the system. It maintains a
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  * registry of drivers and locates the appropriate driver to handle a
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  * JDBC database URL.
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  * <p>
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  * On startup, <code>DriverManager</code> loads all the managers specified
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  * by the system property <code>jdbc.drivers</code>.  The value of this
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  * property should be a colon separated list of fully qualified driver
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  * class names.  Additional drivers can be loaded at any time by
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  * simply loading the driver class with <code>class.forName(String)</code>.
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  * The driver should automatically register itself in a static 
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  * initializer.
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  * <p>
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  * The methods in this class are all <code>static</code>. This class
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  * cannot be instantiated.
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  *
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  * @author Aaron M. Renn (arenn@urbanophile.com)
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  */
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public class DriverManager 
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{
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  /**
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   * This is the log stream for JDBC drivers.
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   */
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  private static PrintStream log_stream;
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  /**
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   * This is the log writer for JDBC drivers.
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   */
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  private static PrintWriter log_writer;
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  /**
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   * This is the login timeout used by JDBC drivers.
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   */
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  private static int login_timeout;
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  /**
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   * This is the list of JDBC drivers that are loaded.
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   */
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  private static Vector drivers;
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   // Hmm, seems like we might want to do a Hashtable and lookup by something,
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   // but what would it be?
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  // Load all drivers on startup
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  static
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  {
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    drivers = new Vector();
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    String driver_string = System.getProperty("jdbc.drivers");
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    if (driver_string != null)
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      {
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	StringTokenizer st = new StringTokenizer(driver_string);
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	while (st.hasMoreTokens())
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          {
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            String driver_classname = st.nextToken();
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            try
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              {
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        	Class.forName(driver_classname); // The driver registers itself
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              }
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            catch (Exception e)
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	      {
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		// Ignore not founds
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	      }
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          }
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      }
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  }
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  /** Can't be instantiated. */
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  private DriverManager()
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  {
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  }
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  /**
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   * This method returns the log writer being used by all JDBC drivers.
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   * This method should be used in place of the deprecated
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   * <code>getLogStream</code> method.
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   *
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   * @return The log writer in use by JDBC drivers.
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   */
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  public static PrintWriter getLogWriter()
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  {
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    return log_writer;
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  }
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  /**
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   * This method sets the log writer being used by JDBC drivers.  This is a
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   * system-wide parameter that affects all drivers.  Note that since there
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   * is no way to retrieve a <code>PrintStream</code> from a 
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   * <code>PrintWriter</code>, this method cannot set the log stream in
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   * use by JDBC.  Thus any older drivers may not see this setting.
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   *
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   * @param out The new log writer for JDBC.
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   */
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  public static void setLogWriter(PrintWriter out)
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  {
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    DriverManager.log_writer = out;
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  }
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/**
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  * This method attempts to return a connection to the specified
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  * JDBC URL string using the specified connection properties.
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  *
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  * @param url The JDBC URL string to connect to.
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  * @param properties The connection properties.
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  *
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  * @return A <code>Connection</code> to that URL.
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  *
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  * @exception SQLException If an error occurs.
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  */
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  public static Connection getConnection(String url, Properties properties)
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    throws SQLException
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  {
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    Driver d = getDriver(url);
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    if (d == null)
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      throw new SQLException("Driver not found for URL: " + url);
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    return d.connect(url, properties);
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  }
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  /**
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   * This method attempts to return a connection to the specified
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   * JDBC URL string using the specified username and password.
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   *
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   * @param url The JDBC URL string to connect to.
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   * @param user The username to connect with.
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   * @param password The password to connect with.
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   * @return A <code>Connection</code> to that URL.
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   * @exception SQLException If an error occurs.
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   */
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  public static Connection getConnection(String url, String user,
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    String password) throws SQLException
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  {
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    Properties p = new Properties();
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    if (user != null)
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      p.setProperty("user", user);
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    if (password != null)
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      p.setProperty("password", password);
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    return getConnection(url, p);
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  }
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  /**
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   * This method attempts to return a connection to the specified
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   * JDBC URL string.
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   *
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   * @param url The JDBC URL string to connect to.
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   *
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   * @return A <code>Connection</code> to that URL.
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   *
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   * @exception SQLException If an error occurs.
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   */
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  public static Connection getConnection(String url) throws SQLException
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  {
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    return getConnection(url, new Properties());
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  }
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  /**
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   * This method returns a driver that can connect to the specified
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   * JDBC URL string.  This will be selected from among drivers loaded
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   * at initialization time and those drivers manually loaded by the
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   * same class loader as the caller.
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   *
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   * @param url The JDBC URL string to find a driver for.
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   *
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   * @return A <code>Driver</code> that can connect to the specified
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   * URL.
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   *
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   * @exception SQLException If an error occurs, or no suitable driver can be found.
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   */
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  public static Driver getDriver(String url) throws SQLException
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  {
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    // FIXME: Limit driver search to the appropriate subset of loaded drivers.
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    Enumeration e = drivers.elements();
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    while(e.hasMoreElements())
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      {
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	Driver d = (Driver)e.nextElement();
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	if (d.acceptsURL(url))
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          return d;
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      }
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    throw new SQLException("No driver found for " + url);
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  }
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  /**
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   * This method registers a new driver with the manager.  This is normally
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   * called by the driver itself in a static initializer.
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   *
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   * @param driver The new <code>Driver</code> to add.
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   *
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   * @exception SQLException If an error occurs.
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   */
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  public static void registerDriver(Driver driver) throws SQLException
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  {
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    if (! drivers.contains(driver))
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      drivers.addElement(driver);  
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  }
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/**
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  * This method de-registers a driver from the manager.
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  *
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  * @param driver The <code>Driver</code> to unregister.
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  *
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  * @exception SQLException If an error occurs.
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  */
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  public static void deregisterDriver(Driver driver) throws SQLException
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  {
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    if (drivers.contains(driver))
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      drivers.removeElement(driver);
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  }
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  /**
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   * This method returns a list of all the currently registered JDBC drivers
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   * that were loaded by the current <code>ClassLoader</code>.
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   *
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   * @return An <code>Enumeration</code> of all currently loaded JDBC drivers.
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   */
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  public static Enumeration getDrivers()
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  {
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    Vector v = new Vector();
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    Enumeration e = drivers.elements();
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    // Is this right?
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    ClassLoader cl = Thread.currentThread().getContextClassLoader();
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    while(e.hasMoreElements())
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      {
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	Object obj = e.nextElement();
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	ClassLoader loader = obj.getClass().getClassLoader();
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	if (loader == null)
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	  loader = ClassLoader.getSystemClassLoader();
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	if (! loader.equals(cl))
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	  continue;
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	v.addElement(obj);
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      } 
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    return v.elements();
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  }
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  /**
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   * This method set the login timeout used by JDBC drivers.  This is a
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   * system-wide parameter that applies to all drivers.
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   *
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   * @param login_timeout The new login timeout value.
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   */
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  public static void setLoginTimeout(int seconds)
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  {
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    DriverManager.login_timeout = login_timeout;  
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  }
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  /**
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   * This method returns the login timeout in use by JDBC drivers systemwide.
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   *
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   * @return The login timeout.
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   */
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  public static int getLoginTimeout()
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  {
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    return login_timeout;
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  }
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  /**
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   * This method sets the log stream in use by JDBC.
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   *
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   * @param log_stream The log stream in use by JDBC.
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   *
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   * @deprecated Use <code>setLogWriter</code> instead.
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   */
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  public static void setLogStream(PrintStream out)
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  {
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    DriverManager.log_stream = log_stream;
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  }
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  /**
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   * This method returns the log stream in use by JDBC.
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   *
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   * @return The log stream in use by JDBC.
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   *
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   * @deprecated Use <code>getLogWriter()</code> instead.
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   */
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  public static PrintStream getLogStream()
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  {
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    return log_stream;
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  }
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  /**
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   * This method prints the specified line to the log stream.
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   *
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   * @param str The string to write to the log stream.
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   */
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  public static void println(String message)
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  {
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    if (log_stream != null) // Watch for user not using logging
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      log_stream.println(message);
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  }
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}
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