SLF4J 2.0.19

2026-09-04 - Release of SLF4J 2.0.19

• When the fluent API was used with XLogger/LoggerWrapper in the slf4j-ext module, caller location was incorrectly reported. To correct this, LoggerWrapper now delegates makeLoggingEventBuilder() to the wrapped logger so that the application caller can be correctly extracted. This issue was reported in issues/464.

• In slf4j-api/DefaultLoggingEventBuilder, a failing toString() invocation on a key-value value, including StackOverflowError, no longer aborts logging. The builder now substitutes [FAILED toString()], matching the existing behaviour of MessageFormatter for message arguments. This issue was reported in issues/448.

• The isLoggable() method in SLF4JPlatformLogger now maps System.Logger.Level.ALL and Level.OFF the same way as log(), that is ALL as TRACE and OFF as ERROR, instead of treating both as always loggable. This is a follow-up to the changes introduced in 2.0.17. See issues/430.

• Published JAR files now package each module's own LICENSE.txt under META-INF/. Previously the parent POM copied the repository-root MIT license into every module, so Apache-2.0 modules such as jcl-over-slf4j and log4j-over-slf4j shipped the wrong license text. This issue was reported in issues/465.

• A bit-wise identical binary of this version can be reproduced by building from source code at commit f0fc3e5 associated with the tag v_2.0.19. Release built using Java "21" 2023-10-17 LTS build 21.0.1.+12-LTS-29 under Linux Debian 11.6.

SLF4J 2.0.18

2026-05-12 - Release of SLF4J 2.0.18

• In the logViaLocationAwareLoggerAPI() method of slf4j-api/DefaultLoggingEventBuilder the first marker from the markerList is now passed to locationAwareLogger.log() instead of null.

• The renderLevel() method in slf4j-simple/SimpleLogger now uses CONFIG_PARAMS.warnLevelString for WARN instead of hardcoded "WARN". This issue was reported in issues/471.

• A bit-wise identical binary of this version can be reproduced by building from source code at commit 58b66c2 associated with the tag v_2.0.18. Release built using Java "21" 2023-10-17 LTS build 21.0.1.+12-LTS-29 under Linux Debian 11.6.

SLF4J 2.0.17

2025-02-25 - Release of SLF4J 2.0.17

• As reported in issues/450, in some rare cases where MDC could be initialized before LoggerFactory. Thus, MDC would be stuck using the wrong MDCAdapter instance. To fix this issue LoggerFactory and MDC have been modified. Implementations of SLF4JServiceProvider are encouraged to initialize their mdcAdapter and markerFactory fields as early as possible, preferably at construction time. Note that these changes are transparent to existing logging backends which will continue to work as is.

• In JDK14LoggerAdapter, fixed extraction of the caller in case there exists an additional logging abstaction such as Jboss logging. This issue was reported in issues/425.

• Fixed incorrect interpretation of Level.OFF and Level.ALL in SLF4JPlatformLogger by mapping Level.OFF as Level.ERROR and Level.ALL as Level.TRACE. This issue was reported in issues/430 by Peter Halicky.

• A bit-wise identical binary of this version can be reproduced by building from source code at commit c233ea1 associated with the tag v_2.0.17. Release built using Java "21" 2023-10-17 LTS build 21.0.1.+12-LTS-29 under Linux Debian 11.6.