前后端完全分离:后端响应的都是json数据，而不再是网页。

1. 登录成功或者失败应该返回json数据 2. 当未登录时返回的也是json数据 3. 访问未授权的资源，也要分会json。

1. 登录成功或者失败应该返回json数据

修改登录接口

@Controller
@ResponseBody
public class LoginController {
    @GetMapping("login")
    public CommonResult login(String username, String password) {
        Subject subject = SecurityUtils.getSubject();
        UsernamePasswordToken token = new UsernamePasswordToken(username,password);
        try {
            subject.login(token);
            return new CommonResult(2000,"登陆成功",null);
        }catch (Exception e){
            e.printStackTrace();
            return new CommonResult(5000,"账号密码输入错误",null);
        }
    }
}

2 当未登录时返回的也是json数据

创建一个过滤器，继承登录校验的某个接口。

@Override
  protected boolean onAccessDenied(ServletRequest request, ServletResponse response) throws Exception {
      response.setContentType("application/json;charset=utf-8");
      PrintWriter writer = response.getWriter();
      CommonResult commonResult = new CommonResult(4001, "未登录", null);
      ObjectMapper objectMapper=new ObjectMapper();
      String json = objectMapper.writeValueAsString(commonResult);
      writer.print(json); //响应给客户json数据
      writer.flush();
      writer.close();
      return false;
  }

3 如果没有权限应该返回json数据

@ControllerAdvice
@ResponseBody
public class MyException {
    @ExceptionHandler(value = UnauthorizedException.class)
    public CommonResult auth(UnauthorizedException u){
        u.printStackTrace();
        return new CommonResult(4002,"没有权限",null);
    }
}