code: public static PrintWriter getWriter(HttpServletResponse response) throws IORuntimeException {
  		try {
  			return response.getWriter();
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		}
  	}
docs: 获得PrintWriter
  
  @param response 响应对象{@link HttpServletResponse}
  @return 获得PrintWriter
  @throws IORuntimeException IO异常