Class SLF4JBridgeHandler

  • public class SLF4JBridgeHandler
    extends Handler
    Bridge/route all JUL log records to the SLF4J API.

    Essentially, the idea is to install on the root logger an instance of SLF4JBridgeHandler as the sole JUL handler in the system. Subsequently, the SLF4JBridgeHandler instance will redirect all JUL log records are redirected to the SLF4J API based on the following mapping of levels:

     FINER   -> DEBUG
     FINE    -> DEBUG
     INFO    -> INFO
     SEVER   -> ERROR


     // call only once during initialization time of your application
     // usual pattern: get a Logger and then log a message
     java.util.logging.Logger julLogger = java.util.logging.Logger
     julLogger.fine("hello world"); // this will get redirected to SLF4J

    Please note that translating a java.util.logging event into SLF4J incurs the cost of constructing LogRecord instance regardless of whether the SLF4J logger is disabled for the given level. Consequently, j.u.l. to SLF4J translation can seriously impact on the cost of disabled logging statements (60 fold increase) and a measurable impact on enabled log statements (20% overall increase).

    If application performance is a concern, then use of SLF4JBridgeHandler is appropriate only if few j.u.l. logging statements are in play.

    Christian Stein, Joern Huxhorn, Ceki Gülcü, Darryl Smith, James R. Perkins
    • Constructor Detail

      • SLF4JBridgeHandler

        public SLF4JBridgeHandler()
        Initialize this handler.
    • Method Detail

      • install

        public static void install()
        Adds a SLF4JBridgeHandler instance to jul's root logger.

        This handler will redirect jul logging to SLF4J. However, only logs enabled in j.u.l. will be redirected. For example, if a log statement invoking a j.u.l. logger disabled that statement, by definition, will not reach any SLF4JBridgeHandler instance and cannot be redirected.

      • uninstall

        public static void uninstall()
                              throws SecurityException
        Removes previously installed SLF4JBridgeHandler instances. See also install().
        SecurityException - A SecurityException is thrown, if a security manager exists and if the caller does not have LoggingPermission("control").
      • isInstalled

        public static boolean isInstalled()
                                   throws SecurityException
        Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
      • removeHandlersForRootLogger

        public static void removeHandlersForRootLogger()
        Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
      • close

        public void close()
        No-op implementation.
        Specified by:
        close in class Handler
      • flush

        public void flush()
        No-op implementation.
        Specified by:
        flush in class Handler
      • getSLF4JLogger

        protected Logger getSLF4JLogger​(LogRecord record)
        Return the Logger instance that will be used for logging.
      • callPlainSLF4JLogger

        protected void callPlainSLF4JLogger​(Logger slf4jLogger,
                                            LogRecord record)
      • publish

        public void publish​(LogRecord record)
        Publish a LogRecord.

        The logging request was made initially to a Logger object, which initialized the LogRecord and forwarded it here.

        This handler ignores the Level attached to the LogRecord, as SLF4J cares about discarding log statements.

        Specified by:
        publish in class Handler
        record - Description of the log event. A null record is silently ignored and is not published.