Here how to connect JAVA and ABAP Stack, so that java can retrieve users from ABAP. This is also true for Solution Manager 7.2. Actually solman should configure that by installation of JAVA Stack, however this is not the case, even you are using MP Stack files.

So lets go:

First go to NWA -> Configuration -> Destinations and create a new Destination here named UMEBackendConnection with type RFC Destination
Enter the hostname of your ABAP System, as well as SysNumber(e.g. 00) and SysID(e.g. SA1)
By Logon Data enter the administration user in ABAP (you might first need to create one, maybe copy of DDIC) and the Client should be a working client of Solman. Save.

Ping the destination to ensure there is no errors.

NWA -> Configuration -> Identity Management -> Configuration. Define ABAP System with UMEBackendConnection and set Data Sources to be "Abap System"

Save!

Now Restart JAVA Instance! Do not forget to do that