HttpsUrlConnection SSLHandshakeException certificate_required

如何解决HttpsUrlConnection SSLHandshakeException certificate_required

我正在尝试从 Java 访问我的 api，但出现以下错误：

javax.net.ssl.SSLHandshakeException: Received fatal alert: certificate_required

在我的个人 Windows 计算机上测试代码时没有收到此错误。但是这个错误确实发生在我运行 Ubuntu 和 openjdk 11 的 linux 生产服务器上。

服务器托管在同一台 ubuntu 服务器上，并使用 Cloudflare SSL Full 代理

HttpsURLConnection con = null;
    try {
        URL url = new URL("https://www.example.com/");
        con = (HttpsURLConnection) url.openConnection();
        con.addRequestProperty("XF-Api-Key","key");
        con.addRequestProperty("XF-Api-User","1");
        con.setConnectTimeout(5000);
        con.setReadTimeout(5000);
        con.addRequestProperty("User-Agent","Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0)");
        con.setRequestMethod("GET");
        con.setRequestProperty("Content-Type","application/json");
        try {
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer content = new StringBuffer();
            while ((inputLine = in.readLine()) != null)
                content.append(inputLine);
            in.close();

            System.out.println(content.toString());
        } catch (Exception e) {
            e.printstacktrace();
            BufferedReader in = new BufferedReader(new InputStreamReader(con.getErrorStream()));
            String inputLine;
            StringBuffer content = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                content.append(inputLine);
            }
            in.close();
            System.out.println(content.toString());
        }
    } catch (Exception exp) {
        System.out.println("Cant load data from API");
        exp.printstacktrace();
    } finally {
        if (con != null)
            con.disconnect();
    }

是不是我的 linux 服务器上配置不正确？