The following URL will retrieve the latest version of log4j 1.2.x:
http://repository.sonatype.org/service/local/artifact/maven/redirect?r=central-proxy&g=log4j&a=log4j&v=LATEST
Documented here
Update
Example using curl:
curl -L "http://repository.sonatype.org/service/local/artifact/maven/redirect?r=central-proxy&g=log4j&a=log4j&v=LATEST" -o log4j.jar
Update for Log4j2
Log4j 1.2 is EOL since summer 2015 and is known to be broken in Java 9.
Here is the link for the Log4j artifacts:
- log4j-api: https://repository.sonatype.org/service/local/artifact/maven/redirect?r=central-proxy&g=org.apache.logging.log4j&a=log4j-api&v=LATEST
- log4j-core: https://repository.sonatype.org/service/local/artifact/maven/redirect?r=central-proxy&g=org.apache.logging.log4j&a=log4j-core&v=LATEST