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
SLF4JBridgeHandleras 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
// 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
LogRecordinstance 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
SLF4JBridgeHandleris appropriate only if any one the following two conditions is true:
- few j.u.l. logging statements are in play
- LevelChangePropagator has been installed
As a Java 9/Jigsaw module
Given that to is a reserved keyword under Java 9 within module productions, the MAFIFEST.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).
- Christian Stein, Joern Huxhorn, Ceki Gülcü, Darryl Smith
Constructors Constructor Description
SLF4JBridgeHandler()Initialize this handler.
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description
callLocationAwareLogger(LocationAwareLogger lal, LogRecord record)
callPlainSLF4JLogger(Logger slf4jLogger, LogRecord record)
getSLF4JLogger(LogRecord record)Return the Logger instance that will be used for logging.
install()Adds a SLF4JBridgeHandler instance to jul's root logger.
isInstalled()Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
publish(LogRecord record)Publish a LogRecord.
removeHandlersForRootLogger()Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
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
public SLF4JBridgeHandler()Initialize this handler.
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.
public static void uninstall() throws SecurityExceptionRemoves previously installed SLF4JBridgeHandler instances. See also
SecurityExceptionis thrown, if a security manager exists and if the caller does not have LoggingPermission("control").
public static boolean isInstalled()Returns true if SLF4JBridgeHandler has been previously installed, returns false otherwise.
- true if SLF4JBridgeHandler is already installed, false other wise
public static void removeHandlersForRootLogger()Invoking this method removes/unregisters/detaches all handlers currently attached to the root logger
protected Logger getSLF4JLogger(LogRecord record)Return the Logger instance that will be used for logging.
record- a LogRecord
- an SLF4J logger corresponding to the record parameter's logger name
protected void callLocationAwareLogger(LocationAwareLogger lal, LogRecord record)
publishPublish 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.