code: protected String getSignatureAlgorithmURI(SignatureSigningParameters signingParameters)
              throws MessageEncodingException {
  
          if (signingParameters.getSignatureAlgorithm() != null) {
              return signingParameters.getSignatureAlgorithm();
          }
  
          throw new MessageEncodingException("The signing algorithm URI could not be determined");
      }
docs: Gets the signature algorithm URI to use.
  
  @param signingParameters the signing parameters to use
  
  @return signature algorithm to use with the associated signing credential
  
  @throws MessageEncodingException thrown if the algorithm URI is not supplied explicitly and
  could not be derived from the supplied credential