RFE: SLF4J_ONLY

[vorburger]

In a large project, it can be useful to enforce that everyone is actually using slf4j and not (directly) log4j (v1/v2) or JUL etc.

A new detector checking that any field / import of a type with simple name Logger must be the org.slf4j.Logger can help with this. This is, of course, "just" a kind of "heuristic", but because in e.g. Log4j and JUL and even other project specific logging frameworks (think e.g. io.vertx.core.logging.Logger and what not), such utilities typically are actually named Logger as well, this works quite well in practice.

FYI https://github.com/opendaylight/yangtools/blob/master/common/checkstyle-logging/src/main/java/org/opendaylight/yangtools/checkstyle/LoggerMustBeSlf4jCheck.java

[vorburger]

one can achieve something similar using Checkstyle's IllegalImport like so:

<module name="IllegalImport">
    <property name="illegalPkgs" value="sun, java.util.logging"/>
</module>