  We report discovering an exoplanet from following up a microlensing event
alerted by Gaia. The event Gaia22dkv is toward a disk source rather than the
traditional bulge microlensing fields. Our primary analysis yields a Jovian
planet with M_p = 0.59^{+0.15}_{-0.05} M_J at a projected orbital separation
r_perp = 1.4^{+0.8}_{-0.3} AU, and the host is a ~1.1 M_sun turnoff star at
~1.3 kpc. At r'~14, the host is far brighter than any previously discovered
microlensing planet host, opening up the opportunity of testing the
microlensing model with radial velocity (RV) observations. RV data can be used
to measure the planet's orbital period and eccentricity, and they also enable
searching for inner planets of the microlensing cold Jupiter, as expected from
the ''inner-outer correlation'' inferred from Kepler and RV discoveries.
Furthermore, we show that Gaia astrometric microlensing will not only allow
precise measurements of its angular Einstein radius theta_E, but also directly
measure the microlens parallax vector and unambiguously break a geometric
light-curve degeneracy, leading to definitive characterization of the lens
system.
