By combining the algebraic Bethe ansatz and the off-diagonal Bethe ansatz, we investigate the supersymmetric t − J model with generic open boundaries. The eigenvalues of the transfer matrix are given in terms of an inhomogeneous T − Q relation, and the corresponding eigenstates are expressed in terms of nested Bethe states which have welldefined homogeneous limit. This exact solution provides basis for further analyzing the thermodynamic properties and correlation functions of the model.