//自己編寫一個類PreInterceptor 實現(xiàn) HandlerInterceptor接口 , 重寫preHandle方法
public class PreInterceptor implements HandlerInterceptor {
    //此方法返回true ,請求才能順利到達相應的處理方法中,否則會被攔截
    @Override
    public boolean preHandle(HttpServletRequest request, 
            HttpServletResponse response, Object handler) throws Exception {
        //第三個參數(shù)為目標控制器對象
        HttpSession session= request.getSession();
        //判斷信息是否有效
        Admin admin = (Admin) session.getAttribute("admin");
        if (admin==null){
            response.getWriter().print(202);
            return false;
        }else {
            return true;
        }
    }
}

<!--配置攔截器-->
<mvc:interceptors>
    <mvc:interceptor>
        <!--所有請求都進入攔截器-->
        <mvc:mapping path="/**"/>
        <!--指定哪些請求不進入攔截器-->
        <mvc:exclude-mapping path="/login/login"/>
        <mvc:exclude-mapping path="/css/**"/>
        <mvc:exclude-mapping path="/images/**"/>
        <mvc:exclude-mapping path="/js/**"/>
        <mvc:exclude-mapping path="/**.html"/>
        <!--攔截器實現(xiàn)類-->
        <bean id="login" class="com.ff.ssm.util.PreInterceptor"/>
    </mvc:interceptor>
</mvc:interceptors>

@RestController
@RequestMapping(value = "/login")
public class LoginController {
    @Autowired
    LoginService loginService;
    @PostMapping(value = "/login")
    public CommonResult adminLogin(Admin admin, HttpSession session){
        CommonResult commonResult;
        try {
            Admin admin1 = loginService.login(admin);
            if(admin1==null){
                commonResult=new CommonResult(201,"賬號或密碼錯誤",admin1);
            }else  {
                session.setAttribute("admin",admin1);
                commonResult=new CommonResult(200,"登錄成功",admin1);
            }
        }catch (Exception e){
            commonResult=new CommonResult(500,"登錄失敗","");
        }
        return commonResult;
    }
}