CLIENT POST OLD_URL -> SERVER 302 NEW_URL -> CLIENT POST NEW_URL
实际302,303:重定向改变请求方法从POST到GET的NEW_URL
CLIENT POST OLD_URL -> SERVER 302 NEW_URL -> CLIENT GET NEW_URL (redirect uses GET)
CLIENT POST OLD_URL -> SERVER 303 NEW_URL -> CLIENT GET NEW_URL (redirect uses GET)
307的ACTUAL:重定向在NEW_URL上使用相同的请求方法POST
CLIENT POST OLD_URL -> SERVER 307 NEW_URL -> CLIENT POST NEW_URL