Maven dependency update on commandline
mvn clean install -U
-U means force update of dependencies.
Also, if you want to import the project into eclipse, I first run:
mvn eclipse:eclipse
then run
mvn eclipse:clean
Seems to work for me, but that's just my pennies worth.
If you just want to re-load/update dependencies (I assume, with constantly changing you mean either SNAPSHOTS or local dependencies you update yourself), you can use
mvn dependency:resolve