Testing for empty columns in resultset

On 16.08.2006 15:30 glen RemoveThis @selfs.net wrote:
> This seems too trivial.
> After populating a resultset with a query, what is the best way to test
> if a column is null to avoid the dreaded null pointer exception when
> attempting a tostring() call.
> thanks
>

ResultSet.wasNull() (very important if you use getInt() or other get
methods that return primitive data types)

As an alternative you can always test your return value (if it's an
Object) agains null , e.g:

String value = rs.getString(1);
if (value != null) ....


Thomas


--
It's not a RootKit - it's a Sony
 >> Stay informed about: Testing for empty columns in resultset 

On 16.08.2006 15:50 gself wrote:
> I was hoping for something like an isnull test.
> String value = rs.getString(1); requires an extra creation of a String
> var
> wasNull requires the getString first to set it's status anyway
> Oh well, I'm justing longing for the good old days of 'C' where if you
> could think of it you could do it.

How should the driver decide that without fetching the value from the
server? There is no way around the getXXXX()

Btw: I doubt that rs.getString(1) will create a *new* String (in the
sense that additional memory is allocated to hold the character data)

If the driver simply does a "return value" where value is the String
that it created, no additional memory is required (except for your local
reference).
Even a "return new String(value)" does not copy the character data. The
new String merely references the character array of the source (this is
possible as Strings are imutable)


Thomas


--
It's not a RootKit - it's a Sony
 >> Stay informed about: Testing for empty columns in resultset 

glen.TakeThisOut@selfs.net writes:

> This seems too trivial.
> After populating a resultset with a query, what is the best way to test
> if a column is null to avoid the dreaded null pointer exception when
> attempting a tostring() call.

If all you are going to do with your ResultSet is to print it, I would
do

System.out.println(rs.getObject(x)+" somestring"+...

which would produce
null somestring

I've tried this with integer, varchar and double columns, but I don't
know if it will work for all types (I guess that depends on how the
getObject() method is implemented in the driver)

--
dt
 >> Stay informed about: Testing for empty columns in resultset