When you try execute example NovaListServers from openstack-java-sdk 3.2.2-SNAPSHOT where endpoint configuration is set on OpenStack 2013.2 (Havana) version of openstack you will get exception:

org.codehaus.jackson.map.exc.UnrecognizedPropertyException: Unrecognized field "OS-SRV-USG:launched_at" (Class com.woorea.openstack.nova.model.Server), not marked as ignorable
at [Source: org.glassfish.jersey.message.internal.EntityInputStream@559b808a; line: 1, column: 1877](through reference chain: com.woorea.openstack.nova.model.Servers["servers"]->com.woorea.openstack.nova.model.Server["OS-SRV-USG:launched_at"])

New version of openstack api has new fields in response:
OS-SRV-USG:launched_at
OS-SRV-USG:terminated_at
os-extended-volumes:volumes_attached

but Server class doesn't have this fields