Can you access how far the spring in a SpringJjoint is extended/compressed?

I have a chain of objects connected by SpringJoints. I need to measure the distances between the ends of the objects where the springs are anchored. That is, I need to know the distance between the anchor and connected anchor of the spring joint.

I know how to do this using the objects' transformations, but I know the physics engine is already doing this to compute the spring force. Can I access how far the spring is extended/compressed? Can I get the current force exerted by the spring? I can compute the extension/compression from that.