I'm strunging with deploying my EXTJS 6 app on my java web constainer behind web proxy

my app should run on https://my.domain.com/sencha/ adrress

which is proxied to internal web constainer app http://someWebOne/my-sencha-web-app << web app

the problem is I cant seem to find property to set BASE PATH for my app. So base path for my app is "/sencha" and everything should be loaded from /sencha domain uri

any help appreciated.