Katy Perry and John Mayer leave Osteria Mozza Restaurant on January 4, 2012 in Hollywood. Credit: FameFlynet

Katy Perry and John Mayer can't keep their hands off each other!

After enjoying a meal at West Hollywood Italian eatery Osteria Mozza on Friday, Jan. 4, the couple exited the restaurant hand-in-hand, with Mayer leading his lady protectively down the street. Perry, clad in a forest-green floral dress and carrying a studded leather jacket, held tight to her on-again boyfriend as they made their way back to their car. See more pictures from their date.

"They are seriously in love and exclusive," a friend told Us Weekly recently of the pair, who celebrated Christmas with the "Wide Awake" singer's parents in Santa Barbara, Calif.

Indeed, aside from their brief split in August, the two have been nearly inseparable since first hooking up in June 2011. Last month, they bonded with Mayer's dad, Richard, at a performance of A Christmas Story on Broadway, where Perry introduced the musician to the cast as her "boyfriend."

"John is surprised at just how cool and smart she is," a pal of the "Born and Raised" songwriter told Us.

Another friend added: "John has proved he's matured and learned from his mistakes...Katy is blown away."