001/* DriverManager.java -- Manage JDBC drivers
002   Copyright (C) 1999, 2000, 2001, 2003, 2004, 2006
003   Free Software Foundation, Inc.
004
005This file is part of GNU Classpath.
006
007GNU Classpath is free software; you can redistribute it and/or modify
008it under the terms of the GNU General Public License as published by
009the Free Software Foundation; either version 2, or (at your option)
010any later version.
011 
012GNU Classpath is distributed in the hope that it will be useful, but
013WITHOUT ANY WARRANTY; without even the implied warranty of
014MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
015General Public License for more details.
016
017You should have received a copy of the GNU General Public License
018along with GNU Classpath; see the file COPYING.  If not, write to the
019Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02002110-1301 USA.
021
022Linking this library statically or dynamically with other modules is
023making a combined work based on this library.  Thus, the terms and
024conditions of the GNU General Public License cover the whole
025combination.
026
027As a special exception, the copyright holders of this library give you
028permission to link this library with independent modules to produce an
029executable, regardless of the license terms of these independent
030modules, and to copy and distribute the resulting executable under
031terms of your choice, provided that you also meet, for each linked
032independent module, the terms and conditions of the license of that
033module.  An independent module is a module which is not derived from
034or based on this library.  If you modify this library, you may extend
035this exception to your version of the library, but you are not
036obligated to do so.  If you do not wish to do so, delete this
037exception statement from your version. */
038
039package java.sql;
040
041import java.io.PrintStream;
042import java.io.PrintWriter;
043import java.util.Enumeration;
044import java.util.Properties;
045import java.util.StringTokenizer;
046import java.util.Vector;
047
048/**
049  * This class manages the JDBC drivers in the system. It maintains a
050  * registry of drivers and locates the appropriate driver to handle a
051  * JDBC database URL.
052  * <p>
053  * On startup, <code>DriverManager</code> loads all the managers specified
054  * by the system property <code>jdbc.drivers</code>.  The value of this
055  * property should be a colon separated list of fully qualified driver
056  * class names.  Additional drivers can be loaded at any time by
057  * simply loading the driver class with <code>class.forName(String)</code>.
058  * The driver should automatically register itself in a static 
059  * initializer.
060  * <p>
061  * The methods in this class are all <code>static</code>. This class
062  * cannot be instantiated.
063  *
064  * @author Aaron M. Renn (arenn@urbanophile.com)
065  */
066public class DriverManager 
067{
068  /**
069   * This is the log stream for JDBC drivers.
070   */
071  private static PrintStream log_stream;
072
073  /**
074   * This is the log writer for JDBC drivers.
075   */
076  private static PrintWriter log_writer;
077
078  /**
079   * This is the login timeout used by JDBC drivers.
080   */
081  private static int login_timeout;
082
083  /**
084   * This is the list of JDBC drivers that are loaded.
085   */
086  private static Vector drivers;
087   // Hmm, seems like we might want to do a Hashtable and lookup by something,
088   // but what would it be?
089
090  // Load all drivers on startup
091  static
092  {
093    drivers = new Vector();
094
095    String driver_string = System.getProperty("jdbc.drivers");
096    if (driver_string != null)
097      {
098        StringTokenizer st = new StringTokenizer(driver_string);
099        while (st.hasMoreTokens())
100          {
101            String driver_classname = st.nextToken();
102
103            try
104              {
105                Class.forName(driver_classname); // The driver registers itself
106              }
107            catch (Exception e)
108              {
109                // Ignore not founds
110              }
111          }
112      }
113
114  }
115
116  /** Can't be instantiated. */
117  private DriverManager()
118  {
119  }
120
121  /**
122   * This method returns the log writer being used by all JDBC drivers.
123   * This method should be used in place of the deprecated
124   * <code>getLogStream</code> method.
125   *
126   * @return The log writer in use by JDBC drivers.
127   */
128  public static PrintWriter getLogWriter()
129  {
130    return log_writer;
131  }
132  
133  /**
134   * This method sets the log writer being used by JDBC drivers.  This is a
135   * system-wide parameter that affects all drivers.  Note that since there
136   * is no way to retrieve a <code>PrintStream</code> from a 
137   * <code>PrintWriter</code>, this method cannot set the log stream in
138   * use by JDBC.  Thus any older drivers may not see this setting.
139   *
140   * @param out The new log writer for JDBC.
141   */
142  public static void setLogWriter(PrintWriter out)
143  {
144    DriverManager.log_writer = out;
145  }
146
147/**
148  * This method attempts to return a connection to the specified
149  * JDBC URL string using the specified connection properties.
150  *
151  * @param url The JDBC URL string to connect to.
152  * @param properties The connection properties.
153  *
154  * @return A <code>Connection</code> to that URL.
155  *
156  * @exception SQLException If an error occurs.
157  */
158  public static Connection getConnection(String url, Properties properties)
159    throws SQLException
160  {
161    Driver d = getDriver(url);
162    if (d == null)
163      throw new SQLException("Driver not found for URL: " + url);
164
165    return d.connect(url, properties);
166  }
167
168
169  /**
170   * This method attempts to return a connection to the specified
171   * JDBC URL string using the specified username and password.
172   *
173   * @param url The JDBC URL string to connect to.
174   * @param user The username to connect with.
175   * @param password The password to connect with.
176   * @return A <code>Connection</code> to that URL.
177   * @exception SQLException If an error occurs.
178   */
179  public static Connection getConnection(String url, String user,
180    String password) throws SQLException
181  {
182    Properties p = new Properties();
183
184    if (user != null)
185      p.setProperty("user", user);
186    if (password != null)
187      p.setProperty("password", password);
188
189    return getConnection(url, p);
190  }
191
192  /**
193   * This method attempts to return a connection to the specified
194   * JDBC URL string.
195   *
196   * @param url The JDBC URL string to connect to.
197   *
198   * @return A <code>Connection</code> to that URL.
199   *
200   * @exception SQLException If an error occurs.
201   */
202  public static Connection getConnection(String url) throws SQLException
203  {
204    return getConnection(url, new Properties());
205  }
206
207  /**
208   * This method returns a driver that can connect to the specified
209   * JDBC URL string.  This will be selected from among drivers loaded
210   * at initialization time and those drivers manually loaded by the
211   * same class loader as the caller.
212   *
213   * @param url The JDBC URL string to find a driver for.
214   *
215   * @return A <code>Driver</code> that can connect to the specified
216   * URL.
217   *
218   * @exception SQLException If an error occurs, or no suitable driver can be found.
219   */
220  public static Driver getDriver(String url) throws SQLException
221  {
222    // FIXME: Limit driver search to the appropriate subset of loaded drivers.
223    Enumeration e = drivers.elements();
224    while(e.hasMoreElements())
225      {
226        Driver d = (Driver)e.nextElement();
227        if (d.acceptsURL(url))
228          return d;
229      }
230
231    throw new SQLException("No driver found for " + url);
232  }
233
234  /**
235   * This method registers a new driver with the manager.  This is normally
236   * called by the driver itself in a static initializer.
237   *
238   * @param driver The new <code>Driver</code> to add.
239   *
240   * @exception SQLException If an error occurs.
241   */
242  public static void registerDriver(Driver driver) throws SQLException
243  {
244    if (! drivers.contains(driver))
245      drivers.addElement(driver);  
246  }
247
248/**
249  * This method de-registers a driver from the manager.
250  *
251  * @param driver The <code>Driver</code> to unregister.
252  *
253  * @exception SQLException If an error occurs.
254  */
255  public static void deregisterDriver(Driver driver) throws SQLException
256  {
257    if (drivers.contains(driver))
258      drivers.removeElement(driver);
259  }
260
261  /**
262   * This method returns a list of all the currently registered JDBC drivers
263   * that were loaded by the current <code>ClassLoader</code>.
264   *
265   * @return An <code>Enumeration</code> of all currently loaded JDBC drivers.
266   */
267  public static Enumeration<Driver> getDrivers()
268  {
269    Vector v = new Vector();
270    Enumeration e = drivers.elements();
271
272    // Is this right?
273    ClassLoader cl = Thread.currentThread().getContextClassLoader();
274
275    while(e.hasMoreElements())
276      {
277        Object obj = e.nextElement();
278
279        ClassLoader loader = obj.getClass().getClassLoader();
280
281        if (loader == null)
282          loader = ClassLoader.getSystemClassLoader();
283        if (! loader.equals(cl))
284          continue;
285
286        v.addElement(obj);
287      } 
288
289    return v.elements();
290  }
291
292  /**
293   * This method set the login timeout used by JDBC drivers.  This is a
294   * system-wide parameter that applies to all drivers.
295   *
296   * @param seconds The new login timeout value.
297   */
298  public static void setLoginTimeout(int seconds)
299  {
300    DriverManager.login_timeout = seconds;  
301  }
302
303  /**
304   * This method returns the login timeout in use by JDBC drivers systemwide.
305   *
306   * @return The login timeout.
307   */
308  public static int getLoginTimeout()
309  {
310    return login_timeout;
311  }
312
313  /**
314   * This method sets the log stream in use by JDBC.
315   *
316   * @param stream The log stream in use by JDBC.
317   * @deprecated Use <code>setLogWriter</code> instead.
318   */
319  public static void setLogStream(PrintStream stream)
320  {
321    DriverManager.log_stream = stream;
322  }
323
324  /**
325   * This method returns the log stream in use by JDBC.
326   *
327   * @return The log stream in use by JDBC.
328   * @deprecated Use <code>getLogWriter()</code> instead.
329   */
330  public static PrintStream getLogStream()
331  {
332    return log_stream;
333  }
334
335  /**
336   * This method prints the specified line to the log stream.
337   *
338   * @param message The string to write to the log stream.
339   */
340  public static void println(String message)
341  {
342    if (log_stream != null) // Watch for user not using logging
343      log_stream.println(message);
344  }
345}