HTTP 后端无法接收header参数

HTTP 后端无法接收header参数

前后端分离，跨域
前端发送请求

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
       
        String token = request.getHeader("Token");
        if (token.isEmpty()){
            response.setStatus(401);
            response.setCharacterEncoding("utf-8");
            PrintWriter writer = response.getWriter();
            writer.println("未查询到认证信息");
            return false;
        }
        boolean b = authClient.checkToken(token);
        if (!b){
            response.setStatus(401);
            response.setCharacterEncoding("utf-8");
            PrintWriter writer = response.getWriter();
            writer.println("未查询到认证信息");
            return false;
        }
        return true;
    }

后端始终报空指针异常，无法正常获取参数

原因
会在发起正式请求之前先发送一个预检请求OPTIONS，需要将此请求过滤

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        if ("OPTIONS".equals(request.getMethod())){
            return true;
        }
        String token = request.getHeader("Token");
        if (token.isEmpty()){
            response.setStatus(401);
            response.setCharacterEncoding("utf-8");
            PrintWriter writer = response.getWriter();
            writer.println("未查询到认证信息");
            return false;
        }
        boolean b = authClient.checkToken(token);
        if (!b){
            response.setStatus(401);
            response.setCharacterEncoding("utf-8");
            PrintWriter writer = response.getWriter();
            writer.println("未查询到认证信息");
            return false;
        }
        return true;
    }

什么情况下会存在OPTIONS请求
https://blog.csdn.net/weixin_34074740/article/details/91444311