/**   * 获取私钥。   *   * @param filename 私钥文件路径  (required)   * @return 私钥对象   */ public static PrivateKey getPrivateKey(String filename) throws IOException {   String content = new String(Files.readAllBytes(Paths.get(filename)), "utf-8");   try {     String privateKey = content.replace("-----BEGIN PRIVATE KEY-----", "")         .replace("-----END PRIVATE KEY-----", "")         .replaceAll("\\s+", "");     KeyFactory kf = KeyFactory.getInstance("RSA");     return kf.generatePrivate(         new PKCS8EncodedKeySpec(Base64.getDecoder().decode(privateKey)));   } catch (NoSuchAlgorithmException e) {     throw new RuntimeException("当前Java环境不支持RSA", e);   } catch (InvalidKeySpecException e) {     throw new RuntimeException("无效的密钥格式");   } }