code: private String getCerticateSubject(AtomicServiceReference<Object> serviceRef, Properties sslProperties) {
          String certificateDN = null;
          try {
              certificateDN = sslHelper.getClientKeyCertSubject(serviceRef, sslProperties);
          } catch (KeyStoreException ke) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                  Tr.error(tc, "CWKKD0020.ssl.get.certificate.user", MONGO, id, ke);
              }
              throw new RuntimeException(Tr.formatMessage(tc, "CWKKD0020.ssl.get.certificate.user", MONGO, id, ke));
          } catch (CertificateException ce) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                  Tr.error(tc, "CWKKD0020.ssl.get.certificate.user", MONGO, id, ce);
              }
              throw new RuntimeException(Tr.formatMessage(tc, "CWKKD0020.ssl.get.certificate.user", MONGO, id, ce));
          }
  
          // handle null .... cannot find the client key
          if (certificateDN == null) {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                  Tr.error(tc, "CWKKD0026.ssl.certificate.exception", MONGO, id);
              }
              throw new RuntimeException(Tr.formatMessage(tc, "CWKKD0026.ssl.certificate.exception", MONGO, id));
          }
  
          return certificateDN;
      }
docs: Call security code to read the subject name from the key in the keystore
  
  @param serviceRef
  @param sslProperties
  @return