Executing a JAR file straight from a Maven repository

A hacky solution working with Maven 3 would be to use the Maven Dependency Plugin in combination with the Maven Help Plugin to resolve the local repository path:

# Download JAR from Maven repo
mvn dependency:get -DremoteRepositories=http://repo1.maven.org/maven2/ \
                   -DgroupId=some.group.id \
                   -DartifactId=some-artifact-cli \
                   -Dversion=1.0.0 \
                   -Dtransitive=false

# Resolve local repository path
MVN_REPO=$(mvn help:evaluate -Dexpression=settings.localRepository -q -DforceStdout)

# Execute JAR from the local repository
java -jar $MVN_REPO/some/group/id/some-artifact-cli/1.0.0/some-artifact-cli-1.0.0.jar

No, Maven will not do what you are asking for. It is a build tool, intended to build a Java project based on it's pom.xml file which describes the project.

So, you can't run a maven build without a pom.xml file. And if you have a pom.xml, then by definition, you have 'set up a Maven project'.

As @DaveNewton says, you should be able to set up a very small pom.xml with the dependency for the jar file in question, and the exec-maven plugin. I'm afraid that it's just not going to get any simpler than that.