code: private static InitialDirContext createDnsDirContext() {
          Hashtable<String, String> envProps = new Hashtable<String, String>();
          envProps.put(Context.INITIAL_CONTEXT_FACTORY, "com.sun.jndi.dns.DnsContextFactory");
          try {
              return new InitialDirContext(envProps);
          } catch (NamingException e) {
              throw new MongoClientException("Unable to support mongodb+srv// style connections as the 'com.sun.jndi.dns.DnsContextFactory' "
                      + "class is not available in this JRE. A JNDI context is required for resolving SRV records.", e);
          }
      }
docs: /*
  It's unfortunate that we take a runtime dependency on com.sun.jndi.dns.DnsContextFactory.
  This is not guaranteed to work on all JVMs but in practice is expected to work on most.