org.slf4j.bridge
Class SLF4JBridgeHandler

java.lang.Object
  extended by java.util.logging.Handler
      extended by org.slf4j.bridge.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:

 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 one the following two conditions is true:

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

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

Constructor Summary
SLF4JBridgeHandler()
          Initialize this handler.
 
Method Summary
protected  void callLocationAwareLogger(LocationAwareLogger lal, LogRecord record)
           
protected  void callPlainSLF4JLogger(Logger slf4jLogger, LogRecord record)
           
 void close()
          No-op implementation.
 void flush()
          No-op implementation.
protected  Logger getSLF4JLogger(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(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
 

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 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 SecurityException
Removes previously installed SLF4JBridgeHandler instances. See also install().

Throws:
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.

Returns:
true if SLF4JBridgeHandler is already installed, false other wise
Throws:
SecurityException

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 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.


callLocationAwareLogger

protected void callLocationAwareLogger(LocationAwareLogger lal,
                                       LogRecord record)

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
Parameters:
record - Description of the log event. A null record is silently ignored and is not published.


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