Taylor Swift has three words for John Mayer: "Oh, come on!"

The singer, who has been everywhere this week promoting her new album, was put in the hot seat by Katie Couric in an interview airing tomorrow.

During the interview, Katie asks Taylor what she thinks of her ex-boyfriend saying he was "humiliated" by the song "Dear John" ... which was reportedly written about their relationship.

Clearly, she doesn't think much of it. Check out her reaction above!

Swifty also reveals a couple of her exes have written her "very long e-mails" -- and was asked if she's ever written a song that was so mean she didn't release it.

The clip comes after Swift taped another interview with Ellen DeGeneres, where she was grilled over which ex her song "We Are Never Ever Getting Back Together" is about. Check out that hilarious clip below:

UPDATE: Swift was reportedly called it quits with Conor Kennedy  ... wonder if there will be another song?

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