微信jsapi支付v3版本获取商户私钥报错：Illegal base64 character 2e

微信支付v3版本获取商户私钥报错：Illegal base64 character 2e

Exception in thread "main" java.lang.IllegalArgumentException: Illegal base64 character 2e
    at java.util.Base64$Decoder.decode0(Base64.java:714)
    at java.util.Base64$Decoder.decode(Base64.java:526)
    at java.util.Base64$Decoder.decode(Base64.java:549)
    at com.wechat.pay.contrib.apache.httpclient.util.PemUtil.loadPrivateKey(PemUtil.java:31)
    at com.wechat.pay.contrib.apache.httpclient.util.PemUtil.loadPrivateKey(PemUtil.java:52)
    at com.weixin.WxPayUtils.main(WxPayUtils.java:92)

源代码：

/**
     * 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");
     System.out.println("content :"+content);
     try {
       String privateKey = content.replace("-----BEGIN PRIVATE KEY-----", "")
           .replace("-----END PRIVATE KEY-----", "")
           .replaceAll("\\s+", "");

       System.out.println("privateKey :"+privateKey);
       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");
     }
   }

请教是哪里问题？