Package org.slf4j.bridge

Class SLF4JBridgeHandler

  • public class SLF4JBridgeHandler
extends java.util.logging.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: 

     FINEST  -> TRACE
 FINER   -> DEBUG
 FINE    -> DEBUG
 INFO    -> INFO
 WARNING -> WARN
 SEVERE  -> ERROR

    Programmatic installation: 

     // Optionally remove existing handlers attached to j.u.l root logger
 SLF4JBridgeHandler.removeHandlersForRootLogger();  // (since SLF4J 1.6.5)

 // add SLF4JBridgeHandler to j.u.l's root logger, should be done once during
 // the initialization phase of your application
 SLF4JBridgeHandler.install();

    Installation via logging.properties configuration file: 

     // register SLF4JBridgeHandler as handler for the j.u.l. root logger
 handlers = org.slf4j.bridge.SLF4JBridgeHandler

    Once SLF4JBridgeHandler is installed, logging by j.u.l. loggers will be directed to SLF4J. Example: 

     import  java.util.logging.Logger;
 ...
 // usual pattern: get a Logger and then log a message
 Logger julLogger = Logger.getLogger("org.wombat");
 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 increase the cost of disabled logging statements (60 fold or 6000% increase) and measurably impact the performance of enabled log statements (20% overall increase). Please note that as of logback-version 0.9.25, it is possible to completely eliminate the 60-fold translation overhead for disabled log statements with the help of LevelChangePropagator.

    If you are concerned about application performance, then use of SLF4JBridgeHandler is appropriate only if any of the following conditions is true:

    1. few j.u.l. logging statements are in play
    2. LevelChangePropagator has been installed

    As a Java 9/Jigsaw module

    Given that to is a reserved keyword under Java 9 within module productions, the MANIFEST.MF file in jul-to-slf4j.jar declares jul_to_slf4j as its Automatic Module Name. Thus, if your application is Jigsaw modularized, the requires statement in your module-info.java needs to be jul_to_slf4j (note the two underscores).

    Since:
    1.5.1
    Author:
    Christian Stein, Joern Huxhorn, Ceki Gülcü, Darryl Smith

    • Constructor Summary

      Constructors 
      Constructor Description
      SLF4JBridgeHandler()
      Initialize this handler.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      protected void callLocationAwareLogger​(org.slf4j.spi.LocationAwareLogger lal, java.util.logging.LogRecord record)  
      protected void callPlainSLF4JLogger​(org.slf4j.Logger slf4jLogger, java.util.logging.LogRecord record)  
      void close()
      No-op implementation.
      void flush()
      No-op implementation.
      protected org.slf4j.Logger getSLF4JLogger​(java.util.logging.LogRecord record)
      Return the Logger instance that will be used for logging.
      static void install()
      Adds a SLF4JBridgeHandler instance to jul's root logger.
      static boolean isInstalled()
      Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
      void publish​(java.util.logging.LogRecord record)
      Publish a LogRecord.
      static void removeHandlersForRootLogger()
      Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
      static void uninstall()
      Removes previously installed SLF4JBridgeHandler instances.

      • Methods inherited from class java.util.logging.Handler

        getEncoding, getErrorManager, getFilter, getFormatter, getLevel, isLoggable, reportError, setEncoding, setErrorManager, setFilter, setFormatter, setLevel

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Method Detail

      • install

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

        This handler will redirect j.u.l. 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 is disabled, then the corresponding non-event will not reach SLF4JBridgeHandler and cannot be redirected.

      • uninstall

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

      • isInstalled

        public static boolean isInstalled()
        Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
        Returns:
        true if SLF4JBridgeHandler is already installed, false otherwise

      • removeHandlersForRootLogger

        public static void removeHandlersForRootLogger()
        Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
        Since:
        1.6.5

      • close

        public void close()
        No-op implementation.
        Specified by:
        close in class java.util.logging.Handler

      • flush

        public void flush()
        No-op implementation.
        Specified by:
        flush in class java.util.logging.Handler

      • getSLF4JLogger

        protected org.slf4j.Logger getSLF4JLogger​(java.util.logging.LogRecord record)
        Return the Logger instance that will be used for logging.
        Parameters:
        record - a LogRecord
        Returns:
        an SLF4J logger corresponding to the record parameter's logger name

      • callLocationAwareLogger

        protected void callLocationAwareLogger​(org.slf4j.spi.LocationAwareLogger lal,
                                       java.util.logging.LogRecord record)

      • callPlainSLF4JLogger

        protected void callPlainSLF4JLogger​(org.slf4j.Logger slf4jLogger,
                                    java.util.logging.LogRecord record)

      • publish

        public void publish​(java.util.logging.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 java.util.logging.Handler
        Parameters:
        record - Description of the log event. A null record is silently ignored and is not published.