Re: [OJB-developers] Detecting and mapping null Integer values
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Re: [OJB-developers] Detecting and mapping null Integer values
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From: Jakob B. <jbr...@ho...> - 2002-02-14 16:55:11
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hi,
i experimented with mySql. they do not have a real boolean, so when using
rs.getObject() the result is either a Byte or a String leading to an
exception in PersistentField::set(). when using getBoolean() the driver
converts the string ('f' in this case) to a Boolean (false).
jakob
----- Original Message -----
From: "Mahler Thomas" <tho...@it...>
To: "'Darren Syzling'" <Dar...@cw...>;
<obj...@li...>
Sent: Thursday, February 14, 2002 12:16 PM
Subject: AW: [OJB-developers] Detecting and mapping null Integer values
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
> -----Ursprüngliche 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
> Integer values
>
>
> It appears to me there are two choices:
>
> - wasNull
>
> - getObject using a cast, is there any reason this wouldn't
> work ? For example:
>
> case Types.INTEGER :
> {
> result = (Integer)rs.getObject(columnId);
> break;
> }
>
> getObject will return a null reference if the column value is null.
>
>
>
> Darren
>
>
>
> |--------+----------------------->
> | | "Jakob |
> | | Braeuchi" |
> | | <jbraeuchi@ho|
> | | tmail.com> |
> | | |
> | | 02/13/02 |
> | | 07:44 PM |
> | | |
> |--------+----------------------->
>
> >-------------------------------------------------------------
> ---------------|
> |
> |
> | To: "Thomas Mahler"
> <tho...@ho...>, Darren |
> | Syzling/London/CWB@CWB
> |
> | cc:
> obj...@li... |
> | Subject: Re: [OJB-developers] Detecting and
> mapping null Integer |
> | values
> |
>
> >-------------------------------------------------------------
> ---------------|
>
>
>
>
> hi thomas,
>
> what about using wasNull of ResultSet ?
>
> /**
> * 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;
>
> hth jakob
>
> ----- 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
> Integer values
>
>
> > Hi Darren,
> >
> > Darren Syzling wrote:
> >
> > > How can I detect null values for Integer, Long, Double
> etc Java class
> attributes
> > > ? Let's say we're mapping an object which has the
> following attributes:
> > >
> > > class Test
> > > {
> > > Integer id;
> > > String name;
> > > Integer sales;
> > > }
> > >
> > >
> > > Let's assume that both name and sales can be null. When
> retrieving this
> object
> > > from the database using the PersistenceBroker the String
> reference will
> be null
> > > but the sales reference will in fact refer to an Integer
> object with a
> zero
> > > value. If zero is within the valid range how can we
> detect that the
> value is
> > > actually null.
> > >
> > > This appears to boil down to:
> JdbcAccess.getObjectFromColumn. The code
> to
> > > convert a string looks like:
> > >
> > > case Types.VARCHAR:
> > > result = rs.getString(columnId);
> > > break;
> > >
> > > If the string value is null getString will return a null
> reference. But
> for
> > > Integer (and other classes) the following is used:
> > >
> > > case Types.INTEGER:
> > > result = 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
> 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
> second is 2, ...
> > * @return the column value; if the value is SQL
> <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
> created with a
> zero
> > > value.
> > >
> > > The Conversion Strategy stuff appears too late in the day
> to make the
> > > conversion.
> >
> >
> > You are right, things are already on the wrong track at
> this point....
> >
> > How is everybody else handling this or have I missed something ?
> >
> >
> > cu,
> >
> > Thomas
> >
> >
> > >
> > >
> > > Thanks
> > > Darren
> > >
> > >
> > >
> > >
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