Maven Central jars can be downloaded from:

http://repo1.maven.org/maven2/

And easily with curl, say for Jackson Databind:

curl -R http://repo1.maven.org/maven2/com/fasterxml/jackson/core/jackson-databind/2.9.8/jackson-databind-2.9.8.jar -o jackson-databind-2.9.8.jar

(-R to preserve the original file timestamp)