<dependency>
  <groupId>org.apache.logging.log4j</groupId>
  <artifactId>log4j-slf4j-impl</artifactId>
  <version>2.4.1</version>
</dependency>

'org.apache.logging.log4j:log4j-slf4j-impl:jar:2.4.1'

<dependency org="org.apache.logging.log4j" name="log4j-slf4j-impl" rev="2.4.1">
  <artifact name="log4j-slf4j-impl" type="jar" />
</dependency>

@Grapes(
@Grab(group='org.apache.logging.log4j', module='log4j-slf4j-impl', version='2.4.1')
)

compile 'org.apache.logging.log4j:log4j-slf4j-impl:2.4.1'

[org.apache.logging.log4j/log4j-slf4j-impl "2.4.1"]

libraryDependencies += "org.apache.logging.log4j" % "log4j-slf4j-impl" % "2.4.1"