OpenSAML Object Signing with HSM based cert and key

Question

I am working on a gateway product where we are authenticating users with SAML SSO. Currently we are signing the SAML authN request before posting to IDP with a self signed certificate created locally in the virtual machine. Going forward we are suppose to sign the request with a certificate placed in Thales Luna Network HSM.

Our core application framework in based on JAVA and we are using OpenSAML library to address the signing. After doing some analysis i got to know that OpenSAML is internally using Apache Santuario library to this. But I want to do this signing with OpenSSL instead of the inbuilt framework because we have already done the OpenSSL integration with HSM. So i am looking for a solution where I can sign OpenSAML objects with OpenSSL.

I did some research to achieve this with OpenSSL but in some articles it is mentioned that OpenSSL can't be used for signing XML objects. I am looking for the below workaround to achieve this use case.

1. How i can sign OpenSAML objects with OpenSSL when the certs are placed in Thales Network HSM.
2. Is there any other command line utility or library is there to address the sane use case so that I can take this for reference.

Sample signing code reference what we are currently doing

AuthnRequest authnRequest = createSAMLObject(AuthnRequest.class);
// Setting other params
Issuer issuer = createSAMLObject(Issuer.class);
// Setting other params
authnRequest.setIssuer(issuer);
NameIDPolicy nameIDPolicy = createSAMLObject(NameIDPolicy.class);
// Setting other params
authnRequest.setNameIDPolicy(nameIDPolicy);
authnRequest.setSignature(getSelfSignedCertificateSignature(cacheData.getIdpPreferredSigningAlgorithm()));
XMLObjectProviderRegistrySupport.getMarshallerFactory().getMarshaller(authnRequest).marshall(authnRequest);
Signer.signObject(authnRequest.getSignature());

Any leads will be appreciated.

Thanks