SLF4J News

Please note that you can receive SLF4J related announcements by subscribing to the announce mailing list.

December 13th, 2016 - Release of SLF4J 1.7.22

Add support for OFF level in SimpleLogger. This feature was requested in SLF4J-332.

Allow re-initialization of SimpleLogger by "friends". This change was requested in SLF4J-370 by Christian Schulte.

April 4th, 2016 - Release of SLF4J 1.7.21

Fixed a memory leak due to a race-condition occurring during SLF4J initialization. In that case, some SubstituteLogger instances may continue to accumulate log events until the JVM eventually runs out of memory. This issue was reported in SLF4J-364 by Jeff Flanigan.

LoggerFactory makes sure to release all resources referenced by SubstituteLoggerFactory post-initialization. See also SLF4J-366

March 29th, 2016 - Release of SLF4J 1.7.20

Releases 1.7.19 and 1.7.20 suffer from a memory leak. Please use version 1.7.21 or later instead.

Fixed initialization problem encountered on the Google App Engine platform with SLF4J version 1.7.19 but not other versions. The problem was reported in SLF4J-363 by Osvaldo Pinali Doederlein.

March 14th, 2016 - Release of SLF4J 1.7.19

Releases 1.7.19 and 1.7.20 suffer from a memory leak. Please use version 1.7.21 or later instead.

Fixed NullPointerException thrown by org.slf4j.helpers.SubstituteLogger.isDelegateEventAware( This issue was reported by Jeffrey Zhao in SLF4J-361.

Initialization of the slf4j-log4j12 module is now thread safe fixing SLF4J-358.

Initialization of the slf4j-jdk14 module is now thread safe fixing SLF4J-359.

26th of February, 2016 - Release of SLF4J 1.7.18

Initialization of the slf4j-simple module is now thread safe fixing SLF4J-356.

Fixed Import-Package statement in MANIFEST.MF for the slf4j-log4j12 module. This isssue was reported by Mathieu Sebire in SLF4J-357 who also provided the relevant pull request.

19th of February, 2016 - Release of SLF4J 1.7.17

When running under Android, skip binding ambiguity check during initialization for better performance. The fix introduced in version 1.7.14 was not effective.

11th of February, 2016 - Release of SLF4J 1.7.16

The MANIFEST.MF file in slf4j-api.jar module was missing an export statement for the org.slf4j.event package. MANIFEST.MF files in other modules were missing the mirroring import statements.

9th of February, 2016 - Release of SLF4J 1.7.15

In previous versions of SLF4J, if the application was already multi-threaded at the time the first SLF4J logger was created, logs made during the SLF4J initialization phase were lost. New code added in relation with SLF4J-353 fixes this problem by storing and replaying logging calls made during initialization.

24th of January, 2016 - Release of SLF4J 1.7.14

The assignment of the INITIALIZATION_STATE variable in LoggerFactory is now guaranteed to be consistent for multi-thread initializations. More specifically, only one thread will see INITIALIZATION_STATE as UNINITIALIZED with all other threads observing either ONGOING_INITIALIZATION or the final result of the initialization. However, SLF4J initialization is still non-blocking and re-entrant, in the sense that if some thread tries to obtain loggers during ongoing initialization by another (or same) thread, instances of SubstituteLogger are returned. This fixes SLF4J-167.

Moved delegation check loop from log4j-over-slf4j.jar to slf4j-log4j12.jar for better targeted loop checks. The rationale behind the change is explained by Frans Orsel in SLF4J-345 who also provided the relevant pull request.

During initialization the binding ambiguity check is skipped under Android in order to improve performance. This change was requested by Nitin Verma in SLF4J-328 who also provided the relevant patch.

The StaticMarkerBinder and StaticMDCBinder classes shipping in various SLF4J bindings now offer a getSingletion() method. The org.slf4j.MDC and MarkerFactory classes now perform binding by invoking the getSingleton() method first and if in the presence of an older version of SLF4J with said method missing, then by accessing the SINGLETON field. This backward compatible change was requested by Rufus Alexander in SLF4J-347 in order to implement an SLF4J binding in Clojure, namely slf4j-timbre.

Fix the OSGI Bundle-Version property in the MANIFEST.MF of osgi-over-slf4j module. This issue was reported by Antoine Dessaigne in SLF4J-341.

10th of November, 2015 - Release of SLF4J 1.7.13

Fixed LoggerFactory initialisation problem in presence of SecurityManager denying "createSecurityManager" runtime permission. See SLF4J-324 for further details.

Fixed issue with BasicMDCAdapter leaking MDC information to non-child threads. This problem was reported by Lukasz Cwik in SLF4J-316 who also provided the relavant pull request.

More robust handling of ill-formatted input strings by SLF4JBridgeHandler. This issue was reported in SLF4J-337 by Rodolfo Udo Labsch.

House cleaning of our project's Maven pom.xml files, an initiative undertaken by Jeremy Landis.

Added getAdditivity() method method in Category class in the log4j-over-slf4j module. This addition was requested by Milo Felipe SLF4J-309 with Dimitrios Liapis providing the relavant pull request.

Added the assertLog(boolean, String) method in the Category class, in module log4j-over-slf4j.

In the log4j-over-slf4j module, removed misplaced file. This issue was reported in SLF4J-218 by Joshua M Steward with Alfredo Ramos providing the relavant pull request.

March 26th, 2015 - Release of SLF4J 1.7.12

All java files have been reformatted to with the code formatter style defined in codeStyle.xml. This style uses 4 spaces for indentation and a maximum line width of 160.

As SLF4J requires JDK 1.5 or later, the Bundle-RequiredExecutionEnvironment declaration in the various MANIFEST files have been updated to J2SE-1.5.

Added missing Bundle-ManifestVersion attribute in the MANIFEST files in log4j-over-slf4j. The issue was raised in SLF4J-231 by Nikolas Falco who also provided the the appropriate pull request.

Added getAppender(String) method in Category class in the log4j-over-slf4j module. This addition was requested by Ramon Gordillo in SLF4J-319.

Added setThreshold method in AppenderSkeleton class in the log4j-over-slf4j module. This addition was requested by Dimitrios Liapis who also provided the appropriate pull request.

Added getParent method in Category class in the log4j-over-slf4j module. This addition was requested by Himanshu Bhardwaj in SLF4J-318.

6th of January, 2015 - Release of SLF4J 1.7.10

The MDC.putCloseable method now explicitly returns MDC.MDCloseable instead of the more generic This in turn allows one to write try-with-resources statement without a catch clause. Many thanks to William Delanoue for proposing this change.

The various constructors in FileAppender in the log4j-over-slf4j module are now public.

16th of December, 2014 - Release of SLF4J 1.7.9

Spot incorrectly named loggers by setting the slf4j.detectLoggerNameMismatch system property to true.

Spot incorrectly named loggers by setting the slf4j.detectLoggerNameMismatch system property to true. This significant feature was contributed by Alexander Dorokhine.

Added MDC.putCloseable method so that it can be used as a closeable resource under Java 7.

Added getContext method returning a hashtable in org.apache.log4j.MDC in the log4j-over-slf4j module.

The introduction of the @Nonnull JSR 305 annotation in SLF4J version 1.7.8 causes the Scala compiler to fail. This is issue has been documented in SI-5420. Given that many Scala users will be affected by this issue for the foreseeable future, we have decided to renounce the user of JSR 305 annotations in SLF4J for the time being.

Numerous small code improvements too minor to be listed here.

4th of April, 2014 - Release of SLF4J 1.7.7

SFL4J API now uses generics. This enhancement was contributed by Otavio Garcia. Due to erasure of generics in Java, the changes are backward-compatible.

The slf4j-migrator can now convert statements using the long deprecated Category class.

Added the SimpleLayout and FileAppender classes to the log4j-over-slf4j module.

February 5th, 2014 - Release of SLF4J 1.7.6

Added slf4j-android module to the slf4j distribution. This module is contributed by Andrey Korzhevskiy.

Loggers created during the initialization phase are no longer NOPLoggers which drop all logging calls. Instead, SLF4J now creates substitute loggers which delegate to the appropriate logger implementation after the initilization phase completes. Only calls made to these loggers during the initialization phase are dropped. This enhacement was proposed in bug 311 by Chetan Mehrotra.

Improvements to the exit() and throwing() methods in XLogger. This enhacement was requested in bug 197.

Concunrrency improvement in MessageFormatter. This improvement was contributed by Vivek Pathak in a pull request.

Concunrrency improvement in BasicMarkerFactory. This improvement was contributed by Mikhail Mazursky in a pull request.

JCLLoggerAdapter was incorrectly invoking isDebugEnabled calls in its trace() methods. This issue was reported in bug 281.

In the log4j-over-slf4j module, the setLevel method in the Category class. This fixes bug 279. Alfredo Ramos provied the relevant patch.

In the log4j-over-slf4j module, added empty implementations for OptionHander, WriterAppender, ConsoleAppender and AppenderSkeleton classes.

25th of March, 2013 - Release of SLF4J 1.7.5

Given the significance of these performance improvements, users are highly encouraged to migrate to SLF4J version 1.7.5 or later.

performance improvements The logger factories in most SLF4J modules namely in jcl-over-slf4j, log4j-over-slf4j, slf4j-jcl, slf4j-jdk14, slf4j-log4j12, and slf4j-simple now use a ConcurrentHashMap instead of a regular HashMap to cache logger instances. This change significantly improves logger retrieval times at the cost of some memory overhead. This improvement was requested in bug #298 by Taras Tielkes who also provided the relevant patch.

18th of March, 2013 - Release of SLF4J 1.7.4

Added a package private reset() method to SimpleLoggerFactory for testing purposes.

15th of March, 2013 - Release of SLF4J 1.7.3

The jul-to-slf4j bridge now correctly handles cases where the message string contains {}-placeholders but has no or zero parameters. This fixes bug #212. The relevant patch was provided by Matthew Preston in a git pull request.

Added missing methods and classes in log4j-over-slf4j module for Velocity compatibility. This issue was reported in bug 280 by Thomas Mortagne.

11th of October, 2012 - Release of SLF4J 1.7.2

Added osgi-over-slf4j module which serves as an OSGi LogService implementation delegating to slf4j. This module is maintained by Matt Bishop and Libor Jelinek.

Christian Trutz added missing PatternLayout class as well as several methods in the Logger and Category classes. See commit 442e90ba5785cba9 dated September 27th 2012 for details.

Added org.slf4j.simpleLoggerwarnLevelString in slf4j-simple module.

Fixed bug 272. All Logger implementations shipping with SLF4J use Object... instead of Object[] to avoid compiler warnings.

14th of September, 2012 - Release of SLF4J 1.7.1

SimpleLogger now supports writing to a file. The property names for configuring SimpleLogger have been modified to be consistently in camel case. More configuration options have been added. In the absence of configuration directives, SimpleLogger will behave exactly the same as in the past. If you are one of the few users configuring SimpleLogger with configuration properties, you will need to adapt to the new and more consistent property names.

6th of September, 2012 - Release of SLF4J 1.7.0

SLF4J now requires JDK 1.5.

Printing methods in the Logger interface now offers variants accepting varargs instead of Object[]. Given that under the hood, the Java compiler transforms varargs into an array, this change is totally 100% no-ifs-or-buts backward compatible with all existing client code.

The logger field (of type java.util.logging.Logger) in JDK14LoggerAdapter is now marked as transient. This fixes bug #261, a serialization problem reported by Thorbjørn Ravn Andersen.

11th of June, 2012 - Release of SLF4J 1.6.6

Source repository has been moved to on github.

In case multiple bindings are found on the class path, SLF4J will now output the name of the framework/implementation class it binds with.

SimpleLogger now supports configuration properties.

LoggerWrapper in the slf4j-ext module now correctly deals with markers. This fixes bug #265 reported by Dario Campagna.

The log4j-over-slf4j module now supports legacy projects providing their own log4j LoggerFactory. This fixes bug #234 reported by Laurent Pellegrino with Piotr Jagielski providing the appropriate patch.

4th of June, 2012 - Release of SLF4J 1.6.5

In the slf4j-log4j12 module, upgraded the log4j dependency to version 1.2.17.

Added removeHandlersForRootLogger() method to SLF4JBridgeHandler class.

The log4j-over-slf4j module now exports all its packages in its manifest. This issue was reported in 262 by Mikhail Mazursky who also provided the relevant patch.

October 31st, 2011 - Release of SLF4J 1.6.4

Fixed in thread-safety issues in BasicMDCAdapter fixing bug #203 and bug #224. Note that BasicMDCAdapter is only used with the slf4j-jdk14.jar binding.

BasicMDCAdapter invoked a method introduced in JDK 1.5 preventing it from running under JDK 1.4. Interestingly enough, this issue has never been reported by the user community.

October 17th, 2011 - Release of SLF4J 1.6.3

LogEvent class in slf4j-ext module now correctly passes the event data as a parameter object. This fixes bug #246 reported by Ralph Goers.

Added missing OSGi manifest to the jul-to-slf4j module. This fixes bug #166 reported by Ekkehard Gentz.

In the log4j-over-slf4j module, added missing getAllAppenders() method in Category class. This fixes bug #235 reported by Anthony Whitford.

August 19th, 2011 - Release of SLF4J 1.6.2

Fixed bug #138. SLF4J will no longer complain about multiple SLF4J bindings when running under a Weblogic server.

Fixed bug #228. When running under IBM's JDK, and if no binding can be found, SLF4J will no longer throw a NoClassDefFoundError. Instead, it will default to an NOP implementation. Under the same circumstances but with Sun's JDK, SLF4J already defaulted to an NOP implementation since release 1.6.0.

Added certain missing classes to the log4j-over-slf4j module as requested in bug 225 by Josh Stewart.

July 5th, 2010 - Release of SLF4J 1.6.1

Updated log4j dependency to version 1.2.16 and CAL10N dependency to version 0.7.4.

Fixed missing versioning OSGi metadata in the log4j-over-slf4j module. This problem was reported in bug 187 by David Savage.

May 8th, 2010 - Release of SLF4J 1.6.0

It is expected that all SLF4J releases in the 1.6.x series will be mutually compatible.

As of SLF4J version 1.6.0, in the absence of an SLF4J binding, slf4j-api will default to a no-operation implementation discarding all log requests. Thus, instead of throwing an exception, SLF4J will emit a single warning message about the absence of a binding and proceed to discard all log requests without further protest. See also the relevant section in the user manual.

In the presence of multiple parameters and if the last argument in a logging statement is an exception, then SLF4J will now presume that the user wants the last argument to be treated as an exception and not a simple parameter. See the relevant FAQ entry for further details. This fixes bug 70 submitted by Joern Huxhorn who also provided the relevant patch.

The log method in LocationAwareLogger interface now admits an additional parameter of type Object[] representing additional arguments of the log request. Due to this modification, slf4j-api version 1.6.x will not work with bindings shipping with SLF4J 1.5.x -- bindings shipping with 1.6.x must be used.

Fixed bug 150 by implementing missing resetConfiguration() and shutdown() methods in LogManager (in log4j-over-slf4j) as nop. In addition, the getCurrentLoggers() method has been implemented by returning an empty enumeration.

Fixed bug 170 by a bare-bones implementation of the NDC class in log4j-over-slf4j.

Fixed bug 175 by synchronizing access to the loggerNameList field.

Fixed bug 164 observed when SLF4J artifacts were placed under java.endorsed.dirs.

Fixed sub-optimal list type usage in SLF4JLogFactory as reported in bug 179 by Sebastian Davids.

Fixed documentation inconsistency in SLF4JLog as reported in bug 180 by Sebastian Davids.

February 25th, 2010 - Release of SLF4J 1.5.11

Users yet unfamiliar with SLF4J sometimes unknowingly place both log4j-over-slf4j.jar and slf4j-log4j12.jar simultaneously on the class path causing stack overflow errors. Simultaneously placing both jcl-over-slf4j.jar and slf4j-jcl.jar on the class path, is another occurrence of the same general problem. As of this version, SLF4J preempts the inevitable stack overflow error by throwing an exception with details about the actual cause of the problem. This is deemed to be better than leaving the user wondering about the reasons of the StackOverflowError.

Fixed bug 168. In case log4j-over-slf4j is used and a logback appender requires a third party library which depends on log4j, the log(String FQCN, Priority p, Object msg, Throwable t) method in log4j-over-slf4j's Category class would throw an UnsupportedOperationException. Problem reported by Seth Call.

December 3rd, 2009 - Release of SLF4J 1.5.10

SLF4J version 1.5.10 consist of bug fixes and minor enhancements. It is totally backward compatible with SLF4J version 1.5.8. However, the slf4j-ext module ships with a new package called org.slf4j.cal10n which adds localized/internationalized logging support as a thin layer built upon the CAL10N API.

SLF4J-android, maintained by Thorsten Möller, was added as a daughter project of SLF4J.

Added missing "Export-Package" declaration for cal10n in the OSGi manifest file for sfl4j-ext. This was requested in bug 156 by Pete Muir.

In log4j-over-slf4j, added missing log(...) methods as requested by Zoltan Szel in bug report 139.

In log4j-over-slf4j, added missing LogManager class as requested by Rick Beton in bug report 150.

In the slf4j-ext module, added getCopyOfChildTimeInstruments and getCopyOfGlobalStopWatch methods to the Profiler class. This enables developers to build their own output formatters for a given Profiler. This feature was requested by David Lindelöf in bug 141.

Fixed a NullPointerException occurring in unspecified conditions as described in bug report 146 by Dapeng Ni.

Added missing OSGi manifest to the log4j-over-slf4j module as requested by Wade Poziombka in bug 117.

OSGi manifests produced by SLF4J now replace the '-' character by '.' in compliance with the OSGi specification. This fixes bug 152 according to the patch supplied by Hugues Malphettes.

Fixed packaging issue in jcl104-over-slf4j which inadvertently produced a jar file as described in bug 151 by Jesse McConnell.

June 11th, 2009 - Release of SLF4J 1.5.8

SLF4J version 1.5.8 consist of bug fixes. It is totally backward compatible with SLF4J version 1.5.7.

The Maven pom file for the log4j-over-slf4j module contained a compile time dependency on the slf4j-jdk14 module. The dependency should have been declared in the test scope. This problem was reported by Jean-Luc Geering on the slf4j user list.

June 10th, 2009 - Release of SLF4J 1.5.7

SLF4J version 1.5.7 consist of bug fixes and minor enhancements. It is totally backward compatible with SLF4J version 1.5.6.

In SLF4J versions 1.5.5 and 1.5.6, the LoggerFactory class which is at the core of SLF4J, if a version compatibility issue was detected, accidentally invoked a method which was introduced in JDK 1.5. Thus, instead of issuing a clear warning message, SLF4J would throw a NoClassDefFoundError. Consequently, SLF4J would not run with JDK 1.4 and earlier but only if a version incompatibility issue was present. For example, if you were mixing slf4j-api-1.5.6.jar with slf4j-simple-1.4.2.jar, which are mutually incompatible. Please note that this bug affects only SLF4J versions 1.5.5 and 1.5.6 and only in the presence of incompatible versions of slf4j-api and its binding.

SLF4J will now emit a warning if more than one binding is present on the class path. This enhancement was proposed in bug 132 contributed by by Robert Elliot.

The Log interface implementations in the jcl-over-slf4j module will now correctly cope with serialization. This fixes bug 79 reported by Mathias Bogaert. Many thanks to Eric Vargo for precisely identifying the problem and supplying the corresponding patch.

The log4j-over-slf4j module will now correctly interact with logging frameworks supporting location information such as java.util.logging and logback. This fixes bug 131 reported by Marc Zampetti.

SLF4JBridgeHandler will no longer ignore log records with an empty message. This fixes bug 108 reported by Pepijn Van Eeckhoudt and independently by Dan Lewis.

In case the toString() method of a parameter throws an exception, MessageFormatter will now print an error message, instead of letting the exception bubble higher up as previously. This fixes bug 112 submitted by Joern Huxhorn.

November 21st, 2008 - Release of SLF4J 1.5.6

SLF4J version 1.5.6 consists of bug fixes. Users are encouraged to upgrade to SLF4J version 1.5.6. The upgrade should pose no problems. Nevertheless, you might still want to refer to the SLF4J compatibility report.

Fixed long standing LBCLASSIC-87 and its younger sibling bug 113. With each call to getLogger() method, LoggerContext will now retrieve the ILoggerFactory afresh from StaticLoggerBinder. This change enables context selectors of native implementations, e.g logback, to work correctly.

Fixed bug 114 reported by Jason Arndt. Corrected the way XLogger (in slf4j-ext) passes its fully qualified class name so that the underlying logging system can correctly compute location information.

The install() method of SLF4JBridgeHandler will no longer reset the entire j.u.l. environment but solely add a SLF4JBridgeHandler instance to jul's root logger. By the same token, the uninstall() method will remove previously added SLF4JBridgeHandler instances without making any other modifications to the j.u.l. configuration.

Added MDCStrLookup to slf4j-ext. This class can be used with Apache Commons Lang's StrSubstitutor class to inject values in the SLF4J MDC into strings. Information on StrSubstitutor can be found at StrSubstitutor javadoc.

October 17th, 2008 - Release of SLF4J 1.5.5

The version check mechanism introduced in SLF4J 1.5.4 was inconsistent with the large size of SLF4J's installed user base. We cannot expect external SLF4J implementations to align their release schedule with that of SLF4J. Consequently, this SLF4J version, namely 1.5.5, retains versions checks but as an elective process. For further details see the relevant entry in the FAQ.

You are highly encouraged to upgrade to SLF4J version 1.5.5. The upgrade should pose no problems. Nevertheless, you might still want to refer to the SLF4J compatibility report.

October 16th, 2008 - Release of SLF4J 1.5.4

This version corrects critical bugs.

Fixed critical bug 106. In previous versions of SLF4J, if during the initial binding phase, the underlying logging system's default configuration created or invoked loggers, a NullPointerException would be thrown. Refer to the in error codes document for a fuller explanation.

At initialization time, LoggerFactory will now check that the version of the slf4j-binding matches that of slf4j-api. If there is a mismatch a warning will be issued on the console. This should help users identify SLF4J related problems more quickly.

Improvements in documentation as well as fix for packaging problems related to slf4j-ext module.

SLF4JBridgeHandler (part of jul-to-slf4j) now accounts for loggers with resourceBundle as well parameters. This feature requested by Darryl Smith in bug 98 and by Jarek Gawor in bug 103.

We now say that markers contain references to other markers. We no longer talk about child markers. The javadocs of the Marker interface have been updated to reflect this change. Moreover, the hasChildren() method in the Marker interface has been deprecated and a new method called hasReferences() was added.

September 12th, 2008 - Release of SLF4J 1.5.3

See also the compatibility report for this version.

Added a new module called slf4j-ext for slf4j-extensions. See its documentation for further details.

Fixed bug 71 which was re-opened by Manfred Geiler. SLF4J loggers now survive serialization. By survive serialization, we mean that the deserialized logger instance are fully functional.

The fix for bug 68 as implemented in version 1.5.1 was incomplete. Michael Furman supplied a more complete fix which was incorporated in this release.

When slf4j bridges, e.g. jcl-over-slf4j or log4j-over-slf4j, were used in conjunction with JUL as the underlying logging system, JDK14LoggerAdapter created a LogRecord even for disabled log statements. This performance issue was reported in bug 90 by Matthew Mastracci.

Added support for array values, including multi-dimensional arrays, as parameters. For example,

log.debug("{} {}", "A", new int[] {1, 2}});

will print as "A [1, 2]" instead of "A [I@6ca1c" as previously. This enhancement was proposed by "lizongbo".

Parameter substitution code has been simplified. SLF4J now only cares about the "{}" formatting anchor, that is the '{' character immediately followed by '}'. Previously, the '{' had meaning on its own. As a result of this change, users no longer need to escape the '{' unless it is immediately followed by '}'. Existing messages which escaped standalone '{' character will be printed with a preceding backslash. However, no data loss in the printed messages will occur.

Added missing getInstance methods to the Category class in the log4j-over-slf4j module, fixing bug 95 reported by Michael Rumpf.

June 8th, 2008 - Release of SLF4J 1.5.2

Improvements to SLF4J documentation as well as fix of packaging problems related to jul-to-slf4j.jar and jcl104-over-slf4j.jar.

June 5th, 2008 - Release of SLF4J 1.5.1

See also the compatibility report for this version.

In order to support JCL version 1.1.1, the jcl104-over-slf4j module was renamed as jcl-over-slf4j. SLF4J will no longer ship with jcl104-over-slf4j.jar but with jcl-over-slf4j.jar. The related work responds to enhancement request discussed in bug 85 as reported by Niklas Gustavsson.

The slf4j-jcl binding now depends on commons-logging version 1.1.1 instead of the older 1.0.4

Added a java.util.logging to SLF4J bridge as requested in bug 38 by Christian Stein, David Smiley, Johan Ferner, Joern Huxhorn and others.

Fixed bug 68 reported by Su Chuan and David Rauschenbach. SLF4J requires log4j 1.2.12 or later. However, if an older version of log4j is present (lacking the TRACE level), in order to avoid NoSuchMethodError exceptions, the SLF4J's Log4jLoggerAdapter will map the TRACE level as DEBUG.

Fixed bug 78 reported by Venu Thachappilly. If the argument array passed to a Logger printing method (debug, info, etc.) was null, a NullPointerException was thrown. With the correction, the messagePattern is returned as is, without parameter substitution.

Added the getCopyOfContextMap and setContextMap methods to the MDCAdapter and org.sf4j.MDC classes. This was requested in bug 84 by Anton Tagunov.

Fixed bug 74, an endless recursion problem in Marker.contains method, reported by Michael Newcomb. Also added he getDetachedMarker method to IMarkerFactor and MarkerFactory classes which was indirectly requested in bug 74.

Added the methods getLevel() and getEffectiveLevel() to the Category class in log4j-over-slf4j. This addition was requested in bug 74 by Michael Newcomb.

The SLF4J Migrator tool has been improved to support migration from JUL to SLF4J.

In MarkerIgnoringBase class, corrected mapping of trace methods with markers to their equivalents without marker data. Previously, the mapping was trace to debug. The incorrect mapping affected only calls to the trace method with markers. Interestingly enough, this bug was picked up by new unit tests and has not been reported as a bug by our users.

February 26th, 2008 - Release of SLF4J 1.5.0

A tool called SLF4J Migrator now ships with SLF4J. It can help you migrate your project using JCL or log4j to use SLF4J instead.

Fixed bug 61 reported by Christopher Sahnwaldt. It is now possible to place a backslash in front of a formatting anchor, by escaping the backslash. For example, the call to MessageFormatter.format("C:\\\\{}", "foo") will now correctly return "C:\\foo". The backslash character needs to be escaped in Java, which leads to four backslashes.

Fixed bug 63 reported by Maarten Bosteels. SLF4J now supports MDC for java.util.logging package.

Fixed bug 64 reported by Michal Bernhard. The log4j binding will now alert the user if she uses SLF4J with a version of log4j earlier than 1.2.12.

Fixed bug 65 reported by Ben Gidley. Superfluous <version>${parent.version}</version> lines have been removed from pom.xml files. These lines reportedly confuse certain Maven repositories.

In the org.apache.log4j.Category class, as implemented in the log4j-over-slf4j module, calls to the printing trace() are now correctly mapped to SLF4J's trace() printing method (instead of debug()). Superfluous printing methods with the signature xxxx(Object, Object) and xxxx(String, Object, Object) have been removed.

Fixed bug 67 reported by Chris Custine. The manifest file for jcl104-over-slf4j now correctly declares version 1.0.4 for the exported JCL packages.

Fixed bug 69 reported by Joern Huxhorn, who graciously supplied the fix as well as a test case. The add method in BasicMarker class now correctly prevents multiple addition of the same child. Moreover, the remove method now correctly removes the specified child marker.

Fixed bug 41 reported by Sebastian Davids. The manifest files of various projects now mention J2SE-1.3 as the required execution environment.

Fixed bug 71 reported by Manfred Geiler. The SLF4JLog and SLF4JLocationAwareLog classes are now serializable solving serialization problems encountered with certain libraries which attempt to serialize JCL log instances.

Fixed bug 73 reported by Oleg Smirsky. A "Fragment-Host: slf4j.api" line has been added to every MANIFEST.MF file exporting org.slf4j.impl.

Fixed bug 72 reported by Ian Carr. Performance issues with slf4j-jdk14 for disabled log statements have now been corrected.

August 20th, 2007 - Release of SLF4J 1.4.3

Fixed bug 60 as reported by Costin Leau. OSGI manifest entries now declare the correct SLF4J version.

Clarified the behavior of the various methods methods in the MDC class with respect to "null" parameters. This was requested in bug 58 by Sebastian Davids.

Removed the slf4j-archetype module because nobody seems to have a use for it.

July 12th, 2007 - Release of SLF4J 1.4.2

The log4j-over-slf4j module has been moved back into SLF4J. Originally, this module was part of SLF4J and was moved into logback due to the lack of MDC support in SLF4J. With version 1.4.2 and the addition of MDC support in SLF4J 1.4.1, log4j-over-slf4j returns to its original home. Note that the previous name of the module was log4j-bridge.

Addition of the getMDCAdapter method to org.slf4j.MDC class. This allows access to the actual MDC implementation which can on occasion come in very handy.

July 4th, 2007 - Release of SLF4J 1.4.1

SLF4J now supports Mapped Diagnostic Contexts (MDC) as requested by Andy Gerweck and Steve Ebersole in bug 49.

Fixed bug 53 as reported by Heinrich Nirschl. The public method trace(String) in the Log4jLoggerAdapter class incorrectly called the underlying log4j logger with level DEBUG instead of TRACE.

Fixed various documentation related errors kindly reported by Mark Vedder.

May 16th, 2007 - Release of SLF4J 1.4.0

In response to many user requests over time, the TRACE level has been added to org.slf4j.Logger interface. Please also see the FAQ entry discussing the TRACE level.

Fixed bug 47 as reported by Terry Todd. In previous a SLF4J release the org.apache.commons.logging.impl.SLF4FLogFactory class was renamed as SLF4JLogFactory. The META-INF/services/org.apache.commons.logging.LogFactory resource file had not reflected this change. It does now.

Eric Yung reported that Apache commons-configuration access certain commons-logging classes, namely org.apache.commons.logging.impl.NoOpLog and SimpleLog, directly. Following Eric's suggestion, jcl104-over-slf4j now includes the aforementioned classes.

April 15th, 2007 - Release of SLF4J 1.3.1

In response to a enhancement request made by Michael Newcomb, a marker can now be detached from the internal list of the MarkerFactory that generated it.

Fixed a silly but nonetheless annoying bug where log request of level ERROR made through jcl104-over-slf4j would log twice. This bug was reported and precisely described by Andrew Cooke.

February 25th, 2007 - Release of SLF4J 1.3.0

This release consists of rearrangement of classes among projects. More specifically, the org.slf4j.LoggerFactory class is now packaged within the slf4j-api.jar file instead of the various slf4j bindings. It follows that client code needs to depend on only slf4j-api in order to compile, while the various slf4j bindings are only needed as runtime dependencies. See also the Maven2-related FAQ entry. Given the practical significance of this change, we highly recommend that library-authors upgrade to version 1.3 at their earliest convenience.

Bug number 23 has been fixed, at the cost of minor and backward compatible changes. In other words, jcl104-over-slf4j now preserves caller location information.

It is now possible to obtain the root logger of the underlying logging implementation by requesting a logger named "ROOT". This feature was requested by Sebastien Davids in bug report 35.

For an exact list of changes please refer to the 1.3.0 compatibility report file as generated by clirr.

January 24th, 2007 - Release of SLF4J 1.2

This release includes several modifications to make SLF4J an OSGi-friendly framework. The modules' MANIFEST.MF files now include OSGi metadata. Regarding these improvements, and OSGi in general, the SLF4J project is happy to welcome John E. Conlon as a new committer.

Marker objects are now Serializable.

December 21st, 2006 - Release of SLF4J 1.1.0 (final)

This release consists of minor bug fixes and documentation changes. More importantly, the log4j-over-slf4j module has been moved to the logback project, under the name log4j-bridge.

Added the file "org.apache.commons.logging.LogFactory" under META-INF/services directory which went missing in the 1.1.0 series of SLF4J. This fixes a compatibility problem with Apache Axis which uses its own discovery mechanism, namely, commons-discovery version 0.2. The problem was reported in bug report 33 by David Varnes.

The file jcl104-over-slf4j.jar had various entries missing in its MANIFEST.MF file, as reported by Boris Unkel in bug number 30.

November 16th, 2006 - Release of SLF4J 1.1.0-RC1

This release consists of packaging related bug fix in addition to minor documentation changes.

Contrary to RC0, RC1 no longer uses SNAPSHOT versions for the slf4j-parent pom. The solution to Maven version problem does not work for public projects such as SLF4J because SNAPSHOTs are not allowed on ibiblio.

November 4th, 2006 - Release of SLF4J 1.1.0-RC0

This release consists of bug fixes. Moreover, since the major packaging related changes in 1.1.0-beta0 seem to work well, this release is marked as RC0.

Fixed the JDK 1.5 dependency for the SLF4J build, as reported by Boris Unkel in bug number 28. SLF4J now explicitly declares a dependency on JDK 1.4 in its pom.xml file.

Fixed an incorrect reference to the logback project in slf4j-api pom file. This bug was reported by Boris Unkel in bug number 29.

Fixed a synchronization problem in factories of almost all SLF4J bindings. This bug was reported independently by Howard M. Lewis Ship and Boris Unkel in bug reports 26 and respectively 27.

September 7th, 2006 - Release of SLF4J 1.1.0-beta0

Release 1.1.0-beta0 is a relatively important release with a refactoring of the way class files are organized in jar files. In previous releases, each binding was self-contained in a single jar file. In this release, each and every binding depends on slf4j-api.jar which contains the bulk of the classes required to use SLF4J, except for one or two adapter classes. Only the adapter classes are now shipped with each specific binding jar as appropriate for the underlying logging system..

This release is built using Maven instead of Ant. As for the java code, it has not been changed.

June 8th, 2006 - Release of SLF4J 1.0.2

Release 1.0.2 is a maintenance release containing bug fixes only.

May 1st, 2006 - Release of SLF4J 1.0.1

Release 1.0.1 is a maintenance release containing bug fixes only.

March 8th, 2006 - Release of SLF4J 1.0

This is release labeled as 1.0 (final) contains few relatively minor changes:

February 4th, 2006 - Release of SLF4J 1.0-RC6 and NLOG4J 1.2.22

The MarkingLogger interface has been removed and its contents merged into org.slf4j.Logger. This change should not adversely affect end-users. However, SLF4J bindings need to be updated. This has been done for all the bindings shipped with SLF4J distribution as well as NLOG4J. As for x4juli, the update is planned for its next release.

The merge between the MarkingLogger and Logger interfaces has been motivated by the need to allow end-users to easily switch between logging systems that support markers and those that do not.

Added a default instance to SimpleLoggerFactory to serve as a last resort fallback mechanism. This instance is designed to be used by a very specific group of users, namely for those developing logging systems (e.g. log4j or LOGBack). It is not intended for end-users of the SLF4J API.

January 9th, 2006 - Release of SLF4J 1.0-RC5 and NLOG4J 1.2.21

A maintenance release correcting bugs #11 and #12 and in general improved resilience to null input parameters across implementations. Many thanks to Boris Unckel and Kenneth for reporting the null input issue.

December 27th, 2005 - Release of SLF4J 1.0-RC4 and NLOG4J 1.2.20

The printing methods in org.slf4j.Logger interface now support passing 3 or more parameters in an Object array. This was a frequently requested feature missing in previous versions of SLF4J.

NLOG4J 1.2.20 reflects the addition of new methods in the org.slf4j.Logger interface.

December 8th, 2005 - Release of SLF4J 1.0-RC3

Maintenance release fixing reported bugs #6 and #7.

November 28th, 2005 - Release of SLF4J 1.0-RC2

In response to a request by Greg Wilkins, this release adds the jar file slf4j-jcl.jar, an SLF4J binding for JCL. Please read the gradual migration section in the manual for more details.

November 21st, 2005 - Release of SLF4J 1.0-RC1

A maintenance release correcting bugs #4 and #5. Many thanks to Christian Beil for accurately reporting bug #4.

There has been also an effort to minimize the file sizes of the various jar files produced by SLF4J, resulting in jar files approximately 40% smaller than in version 1.0beta9.

Given that the SLF4J API is now deemed stable, this release is marked as RC1, that is release candidate number 1.

October 19th, 2005 - Release of SLF4J 1.0-beta9

The SLF4J distribution now includes two distinct bindings slf4j-log4j12.jar and slf4j-log4j13.jar in order to differentiate between log4j version 1.2 and version 1.3. This distinction is absolutely necessary because log4j 1.2 and 1.3 are not run-time compatible, although they are mostly compile-time compatible.

October 19th, 2005 - Release of SLF4J 1.0-beta8 and NLOG4J 1.2.18

Added a new SLF4J binding, slf4j-log4j.jar, intended to be used in conjunction with vanilla log4j.jar, as distributed by the Apache Logging Services project. The slf4j-log4j binding is quite similar in structure to the JDK 1.4 binding that existed previously.

The slf4j-log4j binding addresses compatibility problems which arose when copies of both log4j.jar and nlog4j.jar lay on the class path, in particular when it was undesirable or impossible to remove the preexisting log4j.jar file.

Methods in the org.slf4j.Logger interface related to markers were moved to a separate super interface called org.slf4j.MarkingLogger. This refactoring reduces the weight of the Logger interface.

August 28th, 2005 - Release of SLF4J 1.0-beta7 and NLOG4J 1.2.17

Spurred by bug report #3, SLF4J binding code has been refactored and simplified. Logging systems implementing SLF4J interfaces have to have less work in order to bind with SLF4J. Moreover, these changes have no incidence on the published interface of SLF4J.

August 26th, 2005 - Release of SLF4J 1.0-beta6

To ease migration to SLF4J from JCL, this release includes a jar file called jcl-over-slf4j-1.0.4.jar. This jar file can be used as drop-in replacement for JCL version 1.0.4. It implements the public API of JCL using SLF4J underneath.

Thus, you can immediately benefit from the advantages of SLF4J without waiting for all the libraries you depend on to migrate to SLF4J first.

August 16th, 2005 - Release of NLOG4J 1.2.16

This release adds solves a compatibility problem between log4j and nlog4j. Previous to this release, code compiled with log4j would not run correctly with nlog4j.

With the fixes introduced in NLOG4J 1.2.16, code compiled with log4j 1.2.x will run without problems when deployed using NLOG4j.

However, the inverse is not true. Code compiled with nlog4j can only be deployed using nlog4j.

August 12th, 2005 - Release of SLF4J 1.0-beta5 and NLOG4J 1.2.15

This release adds support for the Marker interface. Thus, log statements can be decorated with Marker data allowing more expressive power in the processing of log statements.

For the sake of IoC frameworks, Logger instances can new be queried for their name.

With the addition of markers, sub-domains are no longer needed.

The LoggerFactoryAdapter has been simplified and renamed as ILoggerFactory.

July 5th, 2005 - Release of NLOG4J 1.2.14

This release fixes compatibility problems between NLOG4J and Jakarta Commons Logging.

June 28th, 2005 - Release of SLF4J 1.0-beta4 and NLOG4J 1.2.13

Following discussions on the SLF4J developers list, the signatures of the printing methods in org.slf4j.Logger interface have been modified to admit messages of type String instead of type Object as previously. The current set of printing methods is listed below.

 void debug(String msg); 
 void debug(String format, Object arg); 
 void debug(String format, Object arg1, Object arg2); 
 void debug(String msg, Throwable t); 

 void error(String msg); 
 void error(String format, Object arg;) 
 void error(String format, Object arg1, Object arg2); 
 void error(String msg, Throwable t); 
 void info(String msg); 
 void info(String format, Object arg); 
 void info(String format, Object arg1, Object arg2); 
 void info(String msg, Throwable t); 
 void warn(String msg); 
 void warn(String format, Object arg); 
 void warn(String format, Object arg1, Object arg2); 
 void warn(String msg, Throwable t);  

NLOG4J release 1.2.13 reflects changes in the SLF4J API.

You can download SLF4J and NLOG4J, including full source code, class files and documentation on our download page.

May 17th, 2005 - SLF4J version 1.0-beta-3 released

In response to user comments, the org.slf4j.ULogger interface has been renamed as org.slf4j.Logger.

May 17th, 2005 - NLOG4J version 1.2.12 released

SLF4J.ORG is proud to release NLOG4J 1.2.12, a log4j-replacement with native SLF4J API support. Except for users of LF5, chainsaw or NTEvenAppender, NLOG4J should be considered as a 100% compatible, drop-in replacement for log4j version 1.2.9.

This release reflects changes in the SLF4J API, i.e renaming of org.slf4j.ULogger interface as org.slf4j.Logger.

May 17th, 2005 - SLF4J version 1.0-beta-3 released

SLF4J.ORG is proud to release SLF4J 1.0-beta-3. In response to user comments, the org.slf4j.ULogger interface has been renamed as org.slf4j.Logger.

You can download SLF4J, including full source code, class files and documentation on our download page.

May 14th, 2005 - NLOG4J version 1.2.11 released

SLF4J.ORG is proud to release NLOG4J 1.2.11, a log4j-replacement with native SLF4J API support. Except for users of LF5, chainsaw or NTEvenAppender, NLOG4J should be considered as a 100% compatible, drop-in replacement for log4j version 1.2.9.

You can download NLOG4J version 1.2.11, including full source code, class files and documentation on our download page.

May 4th, 2005 - SLF4J version 1.0-beta-2 released

SLF4J.ORG is proud to release SLF4J 1.0-beta-2. This release contains cosmetic or javadoc changes. For example, the project has a new logo.

You can download SLF4J version 1.0-beta2, including full source code, class files and documentation on our download page.

1 May 2005 - not-log4j-1.2.10 released

Subsequent to the recall of log4j 1.2.10, SLF4J.ORG releases non-log4j-1.2.10 for those interested in SLF4J support in log4j.

You can download not-log4j version 1.2.10, including full source code, class files and documentation on our download page.

22 April 2005 - SLF4J project goes live

The SLF4J project site, including SVN repositories go live. Users can download SLF4J version 1.0-beta1.

15 April 2005 - start of work on SLF4J source code

Start of work on the SLF4j source code.

13 April 2005 - start of work on SLF4J project

Launch of the SLF4J project. Work has begun on the web-site, svn repositories as well as the source code.