  We estimated the spectral evolution of white dwarfs with effective
temperature using the Javalambre Photometric Local Universe Survey (J-PLUS)
second data release (DR2), that provides twelve photometric optical passbands
over 2176 deg2. We analysed 5926 white dwarfs with r <= 19.5 mag in common
between a white dwarf catalog defined from Gaia EDR3 and J-PLUS DR2. We
performed a Bayesian analysis by comparing the observed J-PLUS photometry with
theoretical models of hydrogen (H) and helium (He) dominated atmospheres. We
estimated the PDF for effective temperature (Teff), surface gravity, parallax,
and spectral type; and the probability of having a H-dominated atmosphere (pH)
for each source. We applied a prior in parallax, using Gaia EDR3 measurements
as reference, and derived a self-consistent prior for the atmospheric
composition as a function of Teff. We described the fraction of He-dominated
atmosphere white dwarfs (fHe) with a linear function of Teff at 5000 < Teff <
30000 K. We found fHe = 0.24 +- 0.01 at Teff = 10000 K, a change rate along the
cooling sequence of 0.14 +- 0.02 per 10 kK, and a minimum He-dominated fraction
of 0.08 +- 0.02 at the high-temperature end. We tested the obtained pH by
comparison with spectroscopic classifications, finding that it is reliable. We
estimated the mass distribution for the 351 sources with distance d < 100 pc,
mass M > 0.45 Msun, and Teff > 6000 K. The result for H-dominated white dwarfs
agrees with previous work, with a dominant M = 0.59 Msun peak and the presence
of an excess at M ~ 0.8 Msun. This high-mass excess is absent in the
He-dominated distribution, which presents a single peak. The J-PLUS optical
data provides a reliable statistical classification of white dwarfs into H- and
He-dominated atmospheres. We find a 21 +- 3 % increase in the fraction of
He-dominated white dwarfs from Teff = 20000 K to Teff = 5000 K.
