java接口与实现类传参问题

Question

我想问一下这里的Controller层调用Service接口是怎么传参的，一个接口不是有多个实现类吗，怎么知道下面的AdminService.login()的返回值是哪个
LoginController

public class LoginController {
    @Autowired
    private IAdminService iAdminService;
    @ApiOperation(value = "登录之后返回token对象")
    @PostMapping("/login")
    public RespBean login(@RequestBody AdminLoginParam adminLoginParam, HttpServletRequest request){
        return iAdminService.login(adminLoginParam.getUsername(),adminLoginParam.getPassword(),adminLoginParam.getCode(),request);
    }

AdminService接口

public interface IAdminService extends IService<Admin> {
    //登录之后返回token
    RespBean login(String username, String password, String code, HttpServletRequest request);
}

AdminService实现类

public class AdminServiceImpl implements IAdminService {
    //登录后返回token
    @Override
    public RespBean login(String username, String password, String code, HttpServletRequest request) {
        String kaptcha = (String) request.getSession().getAttribute("kaptcha");
        if (StringUtils.isNullOrEmpty(code) || !kaptcha.equalsIgnoreCase(code)) {
            return RespBean.error("验证码错误，请重新输入！");
        }

Answer 1

返回值不是这个ServiceImpl的login方法最终返回的么