Craft rails application 第一章

直接 sendfile，浏览器会渲染它

http://stackoverflow.com/questions/12277971/using-send-file-to-download-a-file-from-amazon-s3

本地

require "fileutils"
data = File.open("#{Rails.root}/../dfs/pdf/a.pdf")
send_data data.read, type: "application/pdf", disposition: "inline", stream: "true"

服务器

require "open-uri"
data = open("http://www.......    a.pdf")
send_data data.read, type: "application/pdf", disposition: "inline", stream: "true"