Using an Oracle SQL Function from JPA/TopLink

Question

How do I get the return value from a simple (one string input parameter, returns a string) Oracle SQL Function?
Thanks!

Answer 1

If you mean calling a stored function in Oracle, you might try something like:
    ValueReadQuery vrq = new ValueReadQuery();
    SQLCall call = new SQLCall("begin ###res := pkg.funcInp(#inp); end;");
    vrq.setCall(call);
    Query q = em.createNativeQuery("");   // we need a Query; any query would do; we replace its contents below
    ((EJBQuery)q).setDatabaseQuery(vrq);
    q.setParameter("inp", "paramValue");
    String result = (String)q.getSingleResult();
    // #=input; ###=output; ####=input/output;
    // if you want to explicitly specify the type of an output parameter, use #### instead of ###,
    // because pure "output" parameters are always treated as java.lang.StringThis will only work in TopLink Essentials, though. I don't know how to do it in Hibernate. I have dealt mainly with TopLink, and just a little with Hibernate.
In my opinion, it's a HUGE omission not to have support for stored procedures in JPA. Virtually every project I have worked on (in two large companies) has consisted of a large portion of code in stored procedures (sometimes as much as 50% of the overall code). It's a pain to have to go through all that trouble to call the stored procedures.
Also, pay special attention to TopLink's shared L2 cache. If a stored procedure changes something in the database, TopLink won't know about it and chances are that you will end up with stale objects in the cache which you will either have to refresh, or you'd have to invalidate TopLink's cache for these objects.
Best regards,
Bisser