I always assumed it was a combination of the force and his roboticness... He used the force to be able to "catch" the blasts, both controlling his movements/reaction time (much like Luke with the training probe or death star shot) and possibly altering the trajectory of the laserbolts away from his center of mass (can the force do that? I don't see why not if you're good enough...). Then he used his glove & robot hand to actually absorb the energy of the blast. I assumed hsi glove was like his body suit, which was always supposed to be somewhat protective based on the EU stuff available (this is going on the stuff from when I was a kid, back when EU was still fairly sporadic & actually interesting)