  We investigate the angular momentum decomposition with a quantum
electrodynamics example to clarify the proton spin decomposition debates. We
adopt the light-front formalism where the parton model is well defined. We
prove that the sum of fermion and boson angular momenta is equal to half the
sum of the two gravitational form factors $A(0)$ and $B(0)$, as is well known.
However, the suggestion to make a separation of the above relation into the
fermion and boson pieces, as a way to measure the orbital angular momentum of
fermions or bosons, respectively, is not justified from our explicit
calculation.
