零基础入门SpringMVC拦截器的配置与使用

//自己编写一个类PreInterceptor 实现 HandlerInterceptor接口 , 重写preHandle方法
public class PreInterceptor implements HandlerInterceptor {
    //此方法返回true ,请求才能顺利到达相应的处理方法中,否则会被拦截
    @Override
    public boolean preHandle(HttpServletRequest request, 
            HttpServletResponse response, Object handler) throws Exception {
        //第三个参数为目标控制器对象
        HttpSession session= request.getSession();
        //判断信息是否有效
        Admin admin = (Admin) session.getAttribute(\"admin\");
        if (admin==null){
            response.getWriter().print(202);
            return false;
        }else {
            return true;
        }
    }
}

@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,\"账号或密码错误\",admin1);
            }else  {
                session.setAttribute(\"admin\",admin1);
                commonResult=new CommonResult(200,\"登录成功\",admin1);
            }
        }catch (Exception e){
            commonResult=new CommonResult(500,\"登录失败\",\"\");
        }
        return commonResult;
    }
}