Is there a concept of initialization in package?

Question

Hi,
I am trying to simulate object initialization in package.
CREATE OR REPLACE PACKAGE PKG_TEST AS
FUNCTION abc RETURN DATE;
FUNCTION def RETURN DATE;
FUNCTION ghi RETURN DATE;
END;
CREATE OR REPLACE PACKAGE BODY PKG_TEST AS
  FUNCTION abc RETURN DATE IS
  BEGIN
   RETURN SYSDATE;
  END;
  FUNCTION def RETURN DATE IS
  BEGIN
   RETURN SYSDATE-1;
  END;
  FUNCTION ghi RETURN DATE IS
  BEGIN
   RETURN SYSDATE-2;
  END;
BEGIN
  DBMS_OUTPUT.put_line('Body executed');
END;
--test script
-- Created on 21/12/2007 by TANBKT
declare
  -- Local variables here
  i integer;
begin
  -- Test statements here
  for x in 1..2 loop
   DBMS_OUTPUT.put_line('abc:'||PKG_TEST.abc);
   DBMS_OUTPUT.put_line('abc:'||PKG_TEST.def);
   DBMS_OUTPUT.put_line('abc:'||PKG_TEST.ghi);
  end loop;
end;
--Output
Body executed
abc:21-DEC-2007
abc:20-DEC-2007
abc:19-DEC-2007
abc:21-DEC-2007
abc:20-DEC-2007
abc:19-DEC-2007The above shows that the message "Body executed" was printed only once, somehow similar to object/class constructor(i am referring to Java).
Is it safe to deduce above conclusion? Will there be any cases when the message "Body executed" will not be printed at all? (in other words, the initialization didn't take place)
Thanks.

Answer 1

> Is it safe to deduce above conclusion?
Yes and no.
Yes, the main body of a package is executed when the package is loaded. A package is similar to a shared object or dynamic link library - it gets loaded once into session memory (when used) and stays there until unloaded.
The no part - this relates to the "unloaded" portion. PL/SQL state memory can be reset - and under certain circumstances (like re-using sessions for stateless clients) this is usually a given. The package can be invalidated due to an dependent object being "touched" (DDL) - in which case the session state will also be invalid and the package will be recompiled and reloaded.
Thus the "safeness" of your deduction depends on what you want to do using this "load/constructor" feature of packages.