Maven pull an old version of a transitive dependency

Question

I've written a library I've written that depends upon Guava version 20.0 (the last version that is compatible with JDK 1.7)

I've then written an application that uses that library and also uk.org.lidalia:slf4j-test:1.2.0 (with test scope). slf4j-test has a dependency on version 14.0.1 of Guava.

My problem is that my application is seeing two different versions of Guava as transitive dependencies and picks the OLDER version. Now when I call certain methods in my Library I get Class or Method not found exceptions.

I can (and have) excluded Guava as a dependency of slf4j-test, which fixes the problem for now, but the problem will return if I introduce another dependency which uses Guava.

So my question is: Why would Maven pick the older version of a dependency and how do I always make it pick the latest versions.

Answer 1

You cannot force Maven to always pick the latest version. But there are several things you can do:

1. If you declare the dependency in your own pom, this version always wins. So if you have a dependency on guava 20.0 in your pom, you will get exactly this.

2. If this is not suitable, you can put an entry into dependencyManagement which sets the version for guava. This will overwrite all transitively set versions (like the 14.0.1 in your example).

3. The Maven enforcer plugin has a rule that makes sure that all dependencies are evaluated to the latest version - but it does not pick that latest version, it only fails the build if it was not chosen. Then you need to choose it yourself by applying method (1) or (2) above.