Some features of JEE (compatible app servers) require a supported datastore. This usually involves a JDBC datastore (tied to a JNDI name). Using ArangoDB for such features seems to be problematic at present due to absence of a JDBC-compatible driver/wrapper.
Such a wrapper wouldn't need to be 100% compatible. Just support for simple inserts & reads might be sufficient (at least initially): for what i have in mind, it might even work without any support for joins (in reads), & without any support for transactional isolations levels (perhaps with just no-op stubs, etc.).