  We report on mid-rapidity mass spectrum of di-electrons and cross sections of
pseudoscalar and vector mesons via $e^{+}e^{-}$ decays, from $\sqrt{s} = 200$
GeV $p+p$ collisions, measured by the large acceptance experiment STAR at RHIC.
The ratio of the di-electron continuum to the combinatorial background is
larger than 10% over the entire mass range. Simulations of di-electrons from
light-meson decays and heavy-flavor decays (charmonium and open charm
correlation) are found to describe the data. The extracted $\omega\rightarrow
e^{+}e^{-}$ invariant yields are consistent with previous measurements. The
mid-rapidity yields ($dN/dy$) of $\phi$ and $J/\psi$ are extracted through
their di-electron decay channels and are consistent with the previous
measurements of $\phi\rightarrow K^{+}K^{-}$ and $J/\psi\rightarrow
e^{+}e^{-}$. Our results suggest a new upper limit of the branching ratio of
the $\eta \rightarrow e^{+}e^{-}$ of $1.7\times10^{-5}$ at 90% confidence
level.
