App Transport Security (ATS) lets an app add a declaration to its Info.plist file that specifies the domains with which it needs secure communication. ATS prevents accidental disclosure, provides secure default behavior, and is easy to adopt. You should adopt ATS as soon as possible, regardless of whether you’re creating a new app or updating an existing one.
If you’re developing a new app, you should use HTTPS exclusively. If you have an existing app, you should use HTTPS as much as you can right now, and create a plan for migrating the rest of your app as soon as possible.
在iOS9 beta1中，苹果将原http协议改成了https协议，使用 TLS1.2 SSL加密请求数据。
<key>NSAppTransportSecurity</key><dict> <key>NSAllowsArbitraryLoads</key> <true/></dict>