What is the values of the following integral:

$$\int_{w \in S^{n-1}} e^{i\lambda< x,w >} dw.$$ where $\lambda\in\Bbb R, i^2=-1,x\in\Bbb R^n;<,>$ the inner product scalar on $\Bbb R^n$ and $S^{n-1}$ the unit sphere of $\Bbb R^n$.