I want to call a PL/SQL stored procedure from within a Java program via an entity manager:
StoredProcedureQuery storedProcedureQuery = entityManager.createStoredProcedureQuery("someProcedure");
Now my understanding was that I have to call execute() on this storedProcedureQuery in order to execute the procedure and be able to retrieve the OUT-parameters. However, I can retrieve these values without calling the execute()-Method by simply calling
someValue1 = (Integer)storedProcedureQuery.getOutputParameterValue(1);
someValue2 = (Integer)storedProcedureQuery.getOutputParameterValue(2);
How is this possible ? When exactly will the stored procedure be executed in this code snippet? Will the procedure be executed every time when getOutputParameterValue() is called ? Is there any official documentation for this behaviour ?
I am a new learner in his field and as curious as you with the question. However i have taken this opportunity to test it and below is my observation,
According to the documentation execute() returns:
> Return true if the first result corresponds to a result set,
> and false if it is an update count or if there are no results
> other than through IN OUT and OUT parameters, if any.
therefore I would say, the returned true or false doesn't mean a successful or not execution.
Again we must register the parameters before we call to getOutputParameterValue
. If we looked into the implementation of getOutputParameterValue
, we would able to find exactly where the hibernate provider ( which is JPA in case of mine) calls to the actual execution.
Further to how many times the execution happened I tested it in a way to check it by inserting to another table inside the calling procedure.
create table test_procedure_call(msg varchar2(100));
CREATE OR REPLACE PROCEDURE test (
p_in_1 IN NUMBER,
p_out_1 OUT VARCHAR2,
p_out_2 OUT VARCHAR2
) AS
BEGIN
insert into test_procedure_call values ('Executed..');
commit;
select 'FirstName'||' '||'LastName','HR' into p_out_1,p_out_2
from dual
where p_in_1=1;
END;
/
@Test
public void testStoredProcedureQuery() {
StoredProcedureQuery sp = em.createStoredProcedureQuery("test");
// set parameters
sp.registerStoredProcedureParameter("p_in_1", Integer.class, ParameterMode.IN);
sp.registerStoredProcedureParameter("p_out_1", String.class, ParameterMode.OUT);
sp.registerStoredProcedureParameter("p_out_2", String.class, ParameterMode.OUT);
sp.setParameter("p_in_1", 1);
String name = sp.getOutputParameterValue("p_out_1").toString();
String dept = sp.getOutputParameterValue("p_out_2").toString();
System.out.println("Name : " + name);
System.out.println("Department : " + dept);
}
select * from test_procedure_call;
MSG
----------------------------------------------------------------------------------------
Executed..
By this out of the table test_procedure_call, we can confirm it executes only once per test. (as we saw in above example).