Re: [OJB-developers] Detecting and mapping null Integer values

[Jakob B. <jbr...@ho...>]

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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