How to use

decode

method

in

com.nimbusds.jose.util.Base64

/**
 * Decodes this Base64 object to an unsigned big integer.
 *
 * <p>Same as {@code new BigInteger(1, base64.decode())}.
 *
 * @return The resulting big integer.
 */
public BigInteger decodeToBigInteger() {
  return new BigInteger(1, decode());
}

/**
 * Decodes this Base64 object to a string.
 *
 * @return The resulting string, in the UTF-8 character set.
 */
public String decodeToString() {
  return new String(decode(), StandardCharset.UTF_8);
}

  /**
   * Convert secret to bytes honoring {@link RegisteredServiceProperty.RegisteredServiceProperties#TOKEN_SECRETS_ARE_BASE64_ENCODED}
   * config parameter.
   *
   * @param secret                - String to be represented to byte[]
   * @param secretIsBase64Encoded - is this a base64 encoded #secret?
   * @return byte[] representation of #secret
   */
  private static byte[] getSecretBytes(final String secret, final boolean secretIsBase64Encoded) {
    return secretIsBase64Encoded ? new Base64(secret).decode() : secret.getBytes(UTF_8);
  }
}

public void setSecretBase64(final String secret) {
  this.secret = new Base64(secret).decode();
}

private static byte[] getSecretKey() {
  return new Base64(SECRET_KEY).decode();
}

public void setSecretBase64(final String secret) {
  this.secret = new Base64(secret).decode();
}

X509Certificate cert = X509CertUtils.parse(b64List.get(i).decode());

/**
 * Parses a PEM-encoded X.509 certificate.
 *
 * @param pemEncodedCert The PEM-encoded X.509 certificate, as a
 *                       string. May be {@code null}.
 *
 * @return The X.509 certificate, {@code null} if parsing failed.
 */
public static X509Certificate parse(final String pemEncodedCert) {
  if (pemEncodedCert == null || pemEncodedCert.isEmpty()) {
    return null;
  }
  final int markerStart = pemEncodedCert.indexOf(PEM_BEGIN_MARKER);
  if (markerStart < 0) {
    return null;
  }
  String buf = pemEncodedCert.substring(markerStart + PEM_BEGIN_MARKER.length());
  final int markerEnd = buf.indexOf(PEM_END_MARKER);
  if (markerEnd < 0) {
    return null;
  }
  buf = buf.substring(0, markerEnd);
  buf = buf.replaceAll("\\s", "");
  return parse(new Base64(buf).decode());
}

JWSObject jwsObject = JWSObject.parse(reader.readLine());
List<String> certificateChain = jwsObject.getHeader().getX509CertChain().stream().map(c -> base64Service.encodeToString(c.decode()))
    .collect(Collectors.toList());
JWSAlgorithm algorithm = jwsObject.getHeader().getAlgorithm();