As you yourself already stated, EX4300 does not support IPSEC or MPLS (L3 VPN I assume is what you would be looking for?).
2milindmistry already told you solution was to run some Routing protocol, like OSPF, on both L3 links and then you could either let protocol choose best path, or potential enable ECMP to let both pathes, if equal, to be active. You might also want to consider running BFD over OSPF for faster end-to-end failure detection.
@milindmistry has provided you the answer, not sure what the confusion is? Have you asked this question to your local Juniper Partner or Sales team, from whom you purchased the Juniper gear? Both should be able to assist you.