code: protected void setResponseHeaders(HttpServletResponse resp) {
  		// Force resource caching as best as possible
  		resp.setHeader(CACHE_CONTROL_HEADER, CACHE_CONTROL_VALUE);
  		resp.setHeader(LAST_MODIFIED_HEADER, LAST_MODIFIED_VALUE);
  		resp.setHeader(ETAG_HEADER, ETAG_VALUE);
  		Calendar cal = Calendar.getInstance();
  		cal.roll(Calendar.YEAR, 10);
  		resp.setDateHeader(EXPIRES_HEADER, cal.getTimeInMillis());
  	}
docs: Adds aggressive caching headers to the response in order to prevent
  browsers requesting the same file twice.
  
  @param resp
  the response