In the past, boxers have been told to avoid weight training. This was based on the notion that they would become muscle-bound. But this is simply not true. Strength training not only creates stronger athletes but also makes them less prone to injury, increases lactate threshold and improves flexibility.
Resistance training is a component of boxing supplemental exercise.
This means that you are not a bodybuilder nor are you a power lifter. You are a boxer, so train accordingly. Do not go to 7-Eleven and pick up a muscle and fitness magazine and start implementing Dorian Yates's training routine. The exercises are similar, but the recipe is different. If you keep your goals in mind and train accordingly, you will be delighted with your performance in the ring.