code: public AioSession read(CompletionHandler<Integer, AioSession> handler) {
  		if (isOpen()) {
  			this.readBuffer.clear();
  			this.channel.read(this.readBuffer, Math.max(this.readTimeout, 0L), TimeUnit.MILLISECONDS, this, handler);
  		}
  		return this;
  	}
docs: 读取数据到Buffer
  
  @param handler {@link CompletionHandler}
  @return this