Java 讀取 Nginx $ssl_client_s_dn 中文亂碼

解決思路：

1. 獲取證書Base64
2. 生成證書文件
3. 讀取證書信息

代碼以下：

// 取證書 Base64
    String cert = request.getHeader("SSLClientCERT");
    String certBase64 = cert.replaceAll(X509Factory.BEGIN_CERT, "").replaceAll(X509Factory.END_CERT, "");
    byte[] certByte = Base64.decodeBase64(certBase64);
    ByteArrayInputStream is = new ByteArrayInputStream(certByte);
    CertificateFactory cf = CertificateFactory.getInstance("X.509");
    // 生成X509證書
    X509Certificate certFile = (X509Certificate) cf.generateCertificate(is);
    // 獲取使用者
    String name = certFile.getSubjectDN().getName();