AW: [OJB-developers] Detecting and mapping null Integer values
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AW: [OJB-developers] Detecting and mapping null Integer values
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From: Mahler T. <tho...@it...> - 2002-02-14 11:17:49
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Hi all,
I prefer the wasNull() solution as getObject() is Problematic with =
several
JDBC drivers...
I will put this on my todo list !
thanks,
Thomas
> -----Urspr=FCngliche Nachricht-----
> Von: Darren Syzling [mailto:Dar...@cw...]
> Gesendet: Donnerstag, 14. Februar 2002 10:45
> An: obj...@li...;
> tho...@ho...
> Betreff: Re: [OJB-developers] Detecting and mapping null=20
> Integer values
>=20
>=20
> It appears to me there are two choices:
>=20
> - wasNull
>=20
> - getObject using a cast, is there any reason this wouldn't=20
> work ? For example:
>=20
> case Types.INTEGER :
> {
> result =3D (Integer)rs.getObject(columnId);
> break;
> }
>=20
> getObject will return a null reference if the column value is null.
>=20
>=20
>=20
> Darren
>=20
>=20
>=20
> |--------+----------------------->
> | | "Jakob |
> | | Braeuchi" |
> | | <jbraeuchi@ho|
> | | tmail.com> |
> | | |
> | | 02/13/02 |
> | | 07:44 PM |
> | | |
> |--------+----------------------->
> =20
> >-------------------------------------------------------------
> ---------------|
> | =20
> |
> | To: "Thomas Mahler"=20
> <tho...@ho...>, Darren |
> | Syzling/London/CWB@CWB =20
> |
> | cc: =20
> obj...@li... |
> | Subject: Re: [OJB-developers] Detecting and=20
> mapping null Integer |
> | values =20
> |
> =20
> >-------------------------------------------------------------
> ---------------|
>=20
>=20
>=20
>=20
> hi thomas,
>=20
> what about using wasNull of ResultSet ?
>=20
> /**
> * Reports whether
> * the last column read had a value of SQL <code>NULL</code>.
> * Note that you must first call one of the <code>getXXX</code> =
methods
> * on a column to try to read its value and then call
> * the method <code>wasNull</code> to see if the value read was
> * SQL <code>NULL</code>.
> *
> * @return <code>true</code> if the last column value read was SQL
> * <code>NULL</code> and <code>false</code> otherwise
> * @exception SQLException if a database access error occurs
> */
> boolean wasNull() throws SQLException;
>=20
> hth jakob
>=20
> ----- Original Message -----
> From: "Thomas Mahler" <tho...@ho...>
> To: "Darren Syzling" <Dar...@cw...>
> Cc: <obj...@li...>
> Sent: Wednesday, February 13, 2002 8:09 PM
> Subject: Re: [OJB-developers] Detecting and mapping null=20
> Integer values
>=20
>=20
> > Hi Darren,
> >
> > Darren Syzling wrote:
> >
> > > How can I detect null values for Integer, Long, Double=20
> etc Java class
> attributes
> > > ? Let's say we're mapping an object which has the=20
> following attributes:
> > >
> > > class Test
> > > {
> > > Integer id;
> > > String name;
> > > Integer sales;
> > > }
> > >
> > >
> > > Let's assume that both name and sales can be null. When=20
> retrieving this
> object
> > > from the database using the PersistenceBroker the String=20
> reference will
> be null
> > > but the sales reference will in fact refer to an Integer=20
> object with a
> zero
> > > value. If zero is within the valid range how can we=20
> detect that the
> value is
> > > actually null.
> > >
> > > This appears to boil down to:=20
> JdbcAccess.getObjectFromColumn. The code
> to
> > > convert a string looks like:
> > >
> > > case Types.VARCHAR:
> > > result =3D rs.getString(columnId);
> > > break;
> > >
> > > If the string value is null getString will return a null=20
> reference. But
> for
> > > Integer (and other classes) the following is used:
> > >
> > > case Types.INTEGER:
> > > result =3D new Integer(rs.getInt(columnId));
> > > break;
> > >
> >
> >
> >
> > I get your point. But: how should the above code look like to =
handle
> > your problem correctly? I have no idea.
> > If you (or somebody else) tell me how this section should=20
> look like I
> > will change it!
> >
> >
> > java.sql.ResultSet does not tell you that a column is NULL. It just
> > returns a 0. Of course this is wrong. But SUN specified it this =
way.
> > Or am I missing something? From the java.sql.ResultSet Source:
> >
> > /**
> > * Gets the value of the designated column in the current row
> > * of this <code>ResultSet</code> object as
> > * an <code>int</code> in the Java programming language.
> > *
> > * @param columnIndex the first column is 1, the=20
> second is 2, ...
> > * @return the column value; if the value is SQL=20
> <code>NULL</code>,
> > * the value returned is <code>0</code>
> > * @exception SQLException if a database access error occurs
> > */
> > int getInt(int columnIndex) throws SQLException;
> >
> >
> > > getInt will return 0 for null and the an integer will be=20
> created with a
> zero
> > > value.
> > >
> > > The Conversion Strategy stuff appears too late in the day=20
> to make the
> > > conversion.
> >
> >
> > You are right, things are already on the wrong track at=20
> this point....
> >
> > How is everybody else handling this or have I missed something ?
> >
> >
> > cu,
> >
> > Thomas
> >
> >
> > >
> > >
> > > Thanks
> > > Darren
> > >
> > >
> > >
> > >
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