Either one requires a rigid ring or hollow sphere that can be evenly 'balanced' around the central star or planet in (usually) a rotation equal to a circular orbit at the sphere's equator. Closer to that ideal spin rate, the less the ring/sphere tries to implode or throw itself apart. Unfortunately, it still needs fantastical materials to be rigid enough even if it's perfectly spun for the ring, and the sphere's poles present a massive problem...