Serious enhancement bug

Question

Hi,
The following instance field which is marked in the XML metadata as
persistence-none, is not initialized with the enhancement-provided,
protected, no-args constructor (it remains null):
// this field marked as JDO transient
private DecimalFormat formatter = new DecimalFormat("##0.00");
If I create a public no-args constructor, then the field is initialized
correctly when the no-args constructor is called by your implementation.
David Ezzio

Answer 1

Hello David --
I agree that the behavior you're seeing is not intuitive and a pain in
the ass to deal with, but I don't think it is technically a bug.
When you initialize a member variable where it is declared, like so:
public int foo = 10;
java compilers simply add the initialization code to each of your
declared constructors just after the call to super(). In bytecode there
is no concept of initializing a field 'in-line'.
Because of this, there is absolutely no way to a bytecode parser can
differentiate between inline initializations and code present in the
class constructors. So any JDO implementation that uses bytecode
enhancement (like Kodo) is going to leave all fields -- even
non-persistent ones -- with their default values.
Parsing the .java file is out of the question: JDO is clearly not meant
to rely on the presence of these files for enhancement.
It is sometimes possible to guess at what fields are initialized inline
through tbe bytecode line number table, but there is no way to do so in
a robust manner.
The only real way around the problem is to declare your own default
constructor if you have non-persistent fields that must be initialized.
JDO will then use your constructor instead of creating its own.
At least, that's my take on things.
-- Abe White
Kodo Product Team
David Ezzio wrote:
Hi,
The following instance field which is marked in the XML metadata as
persistence-none, is not initialized with the enhancement-provided,
protected, no-args constructor (it remains null):
// this field marked as JDO transient
private DecimalFormat formatter = new DecimalFormat("##0.00");
If I create a public no-args constructor, then the field is initialized
correctly when the no-args constructor is called by your implementation.
David Ezzio