The following is an example to lookup a domain object by Name.

ResourceIdentityInfo networkId =
new ResourceIdentityInfo(
        null, 
"SOUTHWEST-REGION",
"network");
ResourceIdentityInfo deviceId =
    new ResourceIdentityInfo(
        null, 
"R1230-5",
"device");
OperationalDeviceInfo info = api.getOperationalDeviceInfo(networkId, deviceId, false);