Hi,
You will have to then investigate an option for java related monitor that interfaces with the licensing adapater in the java stack. Unfortunately the entries for example as in abap is stored in table SAPLIKEY but these are digitally signed hexadecimal format if Im not mistaken. So not sure how you would be able to determine expiry date from that. Perhaps log a query to sap oss they might be able to advise of assisting or alternate solution.
Regards.
Johan