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1   /**
2    * Copyright (c) 2004-2011 QOS.ch
3    * All rights reserved.
4    *
5    * Permission is hereby granted, free  of charge, to any person obtaining
6    * a  copy  of this  software  and  associated  documentation files  (the
7    * "Software"), to  deal in  the Software without  restriction, including
8    * without limitation  the rights to  use, copy, modify,  merge, publish,
9    * distribute,  sublicense, and/or sell  copies of  the Software,  and to
10   * permit persons to whom the Software  is furnished to do so, subject to
11   * the following conditions:
12   *
13   * The  above  copyright  notice  and  this permission  notice  shall  be
14   * included in all copies or substantial portions of the Software.
15   *
16   * THE  SOFTWARE IS  PROVIDED  "AS  IS", WITHOUT  WARRANTY  OF ANY  KIND,
17   * EXPRESS OR  IMPLIED, INCLUDING  BUT NOT LIMITED  TO THE  WARRANTIES OF
18   * MERCHANTABILITY,    FITNESS    FOR    A   PARTICULAR    PURPOSE    AND
19   * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
20   * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
21   * OF CONTRACT, TORT OR OTHERWISE,  ARISING FROM, OUT OF OR IN CONNECTION
22   * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
23   *
24   */
25  package org.slf4j.bridge;
26  
27  import java.text.MessageFormat;
28  import java.util.MissingResourceException;
29  import java.util.ResourceBundle;
30  import java.util.logging.Handler;
31  import java.util.logging.Level;
32  import java.util.logging.LogManager;
33  import java.util.logging.LogRecord;
34  
35  import org.slf4j.Logger;
36  import org.slf4j.LoggerFactory;
37  import org.slf4j.spi.LocationAwareLogger;
38  
39  // Based on http://bugzilla.slf4j.org/show_bug.cgi?id=38
40  
41  /**
42   * <p>Bridge/route all JUL log records to the SLF4J API.</p>
43   * <p>Essentially, the idea is to install on the root logger an instance of
44   * <code>SLF4JBridgeHandler</code> as the sole JUL handler in the system. Subsequently, the
45   * SLF4JBridgeHandler instance will redirect all JUL log records are redirected
46   * to the SLF4J API based on the following mapping of levels:
47   * </p>
48   * <pre>
49   * FINEST  -&gt; TRACE
50   * FINER   -&gt; DEBUG
51   * FINE    -&gt; DEBUG
52   * INFO    -&gt; INFO
53   * WARNING -&gt; WARN
54   * SEVERE  -&gt; ERROR</pre>
55   * <p><b>Programmatic installation:</b></p>
56   * <pre>
57   * // Optionally remove existing handlers attached to j.u.l root logger
58   * SLF4JBridgeHandler.removeHandlersForRootLogger();  // (since SLF4J 1.6.5)
59  
60   * // add SLF4JBridgeHandler to j.u.l's root logger, should be done once during
61   * // the initialization phase of your application
62   * SLF4JBridgeHandler.install();</pre>
63   * <p><b>Installation via <em>logging.properties</em> configuration file:</b></p>
64   * <pre>
65   * // register SLF4JBridgeHandler as handler for the j.u.l. root logger
66   * handlers = org.slf4j.bridge.SLF4JBridgeHandler</pre>
67   * <p>Once SLF4JBridgeHandler is installed, logging by j.u.l. loggers will be directed to
68   * SLF4J. Example: </p>
69   * <pre>
70   * import  java.util.logging.Logger;
71   * ...
72   * // usual pattern: get a Logger and then log a message
73   * Logger julLogger = Logger.getLogger(&quot;org.wombat&quot;);
74   * julLogger.fine(&quot;hello world&quot;); // this will get redirected to SLF4J</pre>
75   *
76   * <p>Please note that translating a java.util.logging event into SLF4J incurs the
77   * cost of constructing {@link LogRecord} instance regardless of whether the
78   * SLF4J logger is disabled for the given level. <b>Consequently, j.u.l. to
79   * SLF4J translation can seriously increase the cost of disabled logging
80   * statements (60 fold or 6000% increase) and measurably impact the performance of enabled log
81   * statements (20% overall increase).</b> Please note that as of logback-version 0.9.25,
82   * it is possible to completely eliminate the 60 fold translation overhead for disabled
83   * log statements with the help of <a href="http://logback.qos.ch/manual/configuration.html#LevelChangePropagator">LevelChangePropagator</a>.
84   * </p>
85   *
86   * <p>If you are concerned about application performance, then use of <code>SLF4JBridgeHandler</code>
87   * is appropriate only if any one the following two conditions is true:</p>
88   * <ol>
89   * <li>few j.u.l. logging statements are in play</li>
90   * <li>LevelChangePropagator has been installed</li>
91   * </ol>
92   *
93   * @author Christian Stein
94   * @author Joern Huxhorn
95   * @author Ceki G&uuml;lc&uuml;
96   * @author Darryl Smith
97   * @since 1.5.1
98   */
99  public class SLF4JBridgeHandler extends Handler {
100 
101   // The caller is java.util.logging.Logger
102   private static final String FQCN = java.util.logging.Logger.class.getName();
103   private static final String UNKNOWN_LOGGER_NAME = "unknown.jul.logger";
104 
105   private static final int TRACE_LEVEL_THRESHOLD = Level.FINEST.intValue();
106   private static final int DEBUG_LEVEL_THRESHOLD = Level.FINE.intValue();
107   private static final int INFO_LEVEL_THRESHOLD = Level.INFO.intValue();
108   private static final int WARN_LEVEL_THRESHOLD = Level.WARNING.intValue();
109 
110   /**
111    * Adds a SLF4JBridgeHandler instance to jul's root logger.
112    * <p/>
113    * <p/>
114    * This handler will redirect j.u.l. logging to SLF4J. However, only logs enabled
115    * in j.u.l. will be redirected. For example, if a log statement invoking a
116    * j.u.l. logger is disabled, then the corresponding non-event will <em>not</em>
117    * reach SLF4JBridgeHandler and cannot be redirected.
118    */
119   public static void install() {
120     LogManager.getLogManager().getLogger("").addHandler(
121             new SLF4JBridgeHandler());
122   }
123 
124   private static java.util.logging.Logger getRootLogger() {
125     return LogManager.getLogManager().getLogger("");
126   }
127 
128   /**
129    * Removes previously installed SLF4JBridgeHandler instances. See also
130    * {@link #install()}.
131    *
132    * @throws SecurityException A <code>SecurityException</code> is thrown, if a security manager
133    *                           exists and if the caller does not have
134    *                           LoggingPermission("control").
135    */
136   public static void uninstall() throws SecurityException {
137     java.util.logging.Logger rootLogger = getRootLogger();
138     Handler[] handlers = rootLogger.getHandlers();
139     for (int i = 0; i < handlers.length; i++) {
140       if (handlers[i] instanceof SLF4JBridgeHandler) {
141         rootLogger.removeHandler(handlers[i]);
142       }
143     }
144   }
145 
146   /**
147    * Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
148    *
149    * @return
150    * @throws SecurityException
151    */
152   public static boolean isInstalled() throws SecurityException {
153     java.util.logging.Logger rootLogger = getRootLogger();
154     Handler[] handlers = rootLogger.getHandlers();
155     for (int i = 0; i < handlers.length; i++) {
156       if (handlers[i] instanceof SLF4JBridgeHandler) {
157         return true;
158       }
159     }
160     return false;
161   }
162 
163   /**
164    * Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
165    * @since 1.6.5
166    */
167   public static void removeHandlersForRootLogger() {
168     java.util.logging.Logger rootLogger =  getRootLogger();
169     java.util.logging.Handler[] handlers = rootLogger.getHandlers();
170     for (int i = 0; i < handlers.length; i++) {
171       rootLogger.removeHandler(handlers[i]);
172     }
173   }
174 
175 
176   /**
177    * Initialize this handler.
178    */
179   public SLF4JBridgeHandler() {
180   }
181 
182   /**
183    * No-op implementation.
184    */
185   public void close() {
186     // empty
187   }
188 
189   /**
190    * No-op implementation.
191    */
192   public void flush() {
193     // empty
194   }
195 
196   /**
197    * Return the Logger instance that will be used for logging.
198    */
199   protected Logger getSLF4JLogger(LogRecord record) {
200     String name = record.getLoggerName();
201     if (name == null) {
202       name = UNKNOWN_LOGGER_NAME;
203     }
204     return LoggerFactory.getLogger(name);
205   }
206 
207   protected void callLocationAwareLogger(LocationAwareLogger lal,
208                                          LogRecord record) {
209     int julLevelValue = record.getLevel().intValue();
210     int slf4jLevel;
211 
212     if (julLevelValue <= TRACE_LEVEL_THRESHOLD) {
213       slf4jLevel = LocationAwareLogger.TRACE_INT;
214     } else if (julLevelValue <= DEBUG_LEVEL_THRESHOLD) {
215       slf4jLevel = LocationAwareLogger.DEBUG_INT;
216     } else if (julLevelValue <= INFO_LEVEL_THRESHOLD) {
217       slf4jLevel = LocationAwareLogger.INFO_INT;
218     } else if (julLevelValue <= WARN_LEVEL_THRESHOLD) {
219       slf4jLevel = LocationAwareLogger.WARN_INT;
220     } else {
221       slf4jLevel = LocationAwareLogger.ERROR_INT;
222     }
223     String i18nMessage = getMessageI18N(record);
224     lal.log(null, FQCN, slf4jLevel, i18nMessage, null, record.getThrown());
225   }
226 
227   protected void callPlainSLF4JLogger(Logger slf4jLogger, LogRecord record) {
228     String i18nMessage = getMessageI18N(record);
229     int julLevelValue = record.getLevel().intValue();
230     if (julLevelValue <= TRACE_LEVEL_THRESHOLD) {
231       slf4jLogger.trace(i18nMessage, record.getThrown());
232     } else if (julLevelValue <= DEBUG_LEVEL_THRESHOLD) {
233       slf4jLogger.debug(i18nMessage, record.getThrown());
234     } else if (julLevelValue <= INFO_LEVEL_THRESHOLD) {
235       slf4jLogger.info(i18nMessage, record.getThrown());
236     } else if (julLevelValue <= WARN_LEVEL_THRESHOLD) {
237       slf4jLogger.warn(i18nMessage, record.getThrown());
238     } else {
239       slf4jLogger.error(i18nMessage, record.getThrown());
240     }
241   }
242 
243 
244   /**
245    * Get the record's message, possibly via a resource bundle.
246    *
247    * @param record
248    * @return
249    */
250   private String getMessageI18N(LogRecord record) {
251     String message = record.getMessage();
252 
253     if (message == null) {
254       return null;
255     }
256 
257     ResourceBundle bundle = record.getResourceBundle();
258     if (bundle != null) {
259       try {
260         message = bundle.getString(message);
261       } catch (MissingResourceException e) {
262       }
263     }
264     Object[] params = record.getParameters();
265     if (params != null) {
266       message = MessageFormat.format(message, params);
267     }
268     return message;
269   }
270 
271   /**
272    * Publish a LogRecord.
273    * <p/>
274    * The logging request was made initially to a Logger object, which
275    * initialized the LogRecord and forwarded it here.
276    * <p/>
277    * This handler ignores the Level attached to the LogRecord, as SLF4J cares
278    * about discarding log statements.
279    *
280    * @param record Description of the log event. A null record is silently ignored
281    *               and is not published.
282    */
283   public void publish(LogRecord record) {
284     // Silently ignore null records.
285     if (record == null) {
286       return;
287     }
288 
289     Logger slf4jLogger = getSLF4JLogger(record);
290     String message = record.getMessage(); // can be null!
291     // this is a check to avoid calling the underlying logging system
292     // with a null message. While it is legitimate to invoke j.u.l. with
293     // a null message, other logging frameworks do not support this.
294     // see also http://bugzilla.slf4j.org/show_bug.cgi?id=108
295     if (message == null) {
296       message = "";
297     }
298     if (slf4jLogger instanceof LocationAwareLogger) {
299       callLocationAwareLogger((LocationAwareLogger) slf4jLogger, record);
300     } else {
301       callPlainSLF4JLogger(slf4jLogger, record);
302     }
303   }
304 
305 }