This post is older than a year. Consider some information might not be accurate anymore.
Apache Maven relies on dependencies declared in the pom.xml. You could also just use the dependency:get goal to download the artifact.
A simple example for slf4j.
mvn dependency:get -Dartifact=org.slf4j:slf4j-api:1.7.22
mvn dependency:get -Dartifact=ch.qos.logback:logback-classic:1.1.8
