code: protected AttributeCertificate getACFromResponse(VOMSACRequest request,
      VOMSResponse response) {
  
      byte[] acBytes = response.getAC();
  
      if (acBytes == null)
        return null;
  
      ASN1InputStream asn1InputStream = new ASN1InputStream(acBytes);
  
      AttributeCertificate attributeCertificate = null;
  
      try {
  
        attributeCertificate = AttributeCertificate.getInstance(asn1InputStream
          .readObject());
  
        asn1InputStream.close();
        return attributeCertificate;
  
      } catch (Throwable e) {
  
        requestListener.notifyVOMSRequestFailure(request, null, new VOMSError(
          "Error unmarshalling VOMS AC. Cause: " + e.getMessage(), e));
  
        return null;
      }
    }
docs: Extracts an AC from a VOMS response
  
  @param request
  the request
  @param response
  the received response
  @return a possibly <code>null</code> {@link AttributeCertificate} object