Here's an example:
@startuml
autonumber
actor User
participant Server
box "Filter Chain"
participant "Delegating Filter Proxy" as F1
participant "Filter 1" as F2
participant "Filter ..." as F3
participant "Filter n" as F4
end box
participant DispatcherServlet as DS
participant Controller
User -> Server : request
Server -> F1 : request
F1 -> F2
F2 -> F3
F3 -> F4
F4 -> DS
DS -> Controller
autonumber stop
Controller -->> DS
DS -->> F4
F4 -->> F3
F3 -->> F2
F2 -->> F1
F1 -->> Server
Server -->> User
@enduml
It is rendered like this: https://imgur.com/a/T3CQ065 (see Delegating Filter Proxy and DispatcherServlet participants).
Using skinparam padding is not an option here, as it will deform the box (too much whitespace on the left, top, and bottom and very little on the right).
Dot version:
$ dot -V
dot - graphviz version 2.40.1 (20161225.0304)