Upgrading to slf4j 2 (fatal ClassCastException on startup)

[rtyley]

slf4j v2 no longer honours the old static binder mechanism for finding logging providers, meaning that if you upgrade to it, your logging provider & config may not be found. If you're using Logback (Play framework default), you may see a fatal runtime error on startup like this:

SLF4J(W): No SLF4J providers were found.
SLF4J(W): Defaulting to no-operation (NOP) logger implementation
SLF4J(W): See https://www.slf4j.org/codes.html#noProviders for further details.
SLF4J(W): Class path contains SLF4J bindings targeting slf4j-api versions 1.7.x or earlier.
SLF4J(W): Ignoring binding found at [jar:file:/usr/share/tag-manager/lib/ch.qos.logback.logback-classic-1.2.11.jar!/org>
SLF4J(W): See https://www.slf4j.org/codes.html#ignoredBindings for an explanation.
Oops, cannot start the server.
java.lang.ClassCastException: org.slf4j.helpers.NOPLoggerFactory cannot be cast to ch.qos.logback.classic.LoggerContext

Logback v1.3+ copes with the new ServiceLoader mechanism for finding logging providers, and is used by Play v2.9+.

Libraries pulling in slf4j v2

• content-api-client v28.0.0+ (PR #409)