UsernamePasswordAuthenticationTo

UsernamePasswordAuthenticationToken
里面有UserDetails【principal】，credentials，authorities

UserDetails-里面有账号密码

UsernamePasswordAuthenticationToken authentication =
new UsernamePasswordAuthenticationToken(userDetails, null, userDetails.getAuthorities());

authentication.setDetails(new WebAuthenticationDetailsSource().buildDetails(request));
WebAuthenticationDetailsSource是干啥的？