Record audios in webapp and save as mp3 file

Need to add audio record functionality in a jsp based webapp. The flow has to be like ---- record an small audio --> listen to audio --> be able to trim away the starting silent part of audio(The requirement is that sound should come as soon as audio is played. There should'nt be a silence at starting. Usually we record an audio , there is a small amount of delay before we start speaking ) --> save the audio as mp3.