Re: Handling null values in char fields from JDBC

You should use wasNull after each getXxx method if the column being read
allows null. It's as simple as:

text = rs.getString(2);
if (rs.wasNull()) {
System.out.println("This column is SQL null");
} else {
// process data
}

It's particularly useful when you are reading values to basic data type
variables (not objects) because there is no value that uniquely
represents the SQL null. For example getInt returns 0 (zero) if the
value is null but it would also return 0 when the value is zero.
(ResultSet.getString must return null when the column value is null; I'm
using it in Posrgres JDBC driver and it works fine.)

Check
http://java.sun.com/j2se/1.4/docs/api/java/sql/ResultSet.html#wasNull()

Paulo Merson
Summa Technologies - www.summa-tech.com

-----Original Message-----
From: pgsql-jdbc-owner(at)postgresql(dot)org
[mailto:pgsql-jdbc-owner(at)postgresql(dot)org] On Behalf Of Sean Duffy
Sent: Tuesday, January 22, 2002 1:34 PM
To: Paulo Merson; pgsql-jdbc(at)postgresql(dot)org
Subject: Re: [JDBC] Handling null values in char fields from JDBC

-----Original Message-----
From: "Paulo Merson" <paulo(at)summa-tech(dot)com>
Date: Tue, 22 Jan 2002 09:46:44 -0500
To: <pgsql-jdbc(at)postgresql(dot)org>
Subject: Re: [JDBC] Handling null values in char fields from JDBC

Paulo -

I am using ResultSet.getString but Im not
sure how I can use ResultSet.wasNull. Is
there an example I could look at?

Thanks :)

Sean -

> Are you using ResultSet.getString and then ResultSet.wasNull?
>
> Paulo Merson
> Summa Technologies - www.summa-tech.com
>
> -----Original Message-----
> From: pgsql-jdbc-owner(at)postgresql(dot)org
> [mailto:pgsql-jdbc-owner(at)postgresql(dot)org] On Behalf Of Sean Duffy
> Sent: Tuesday, January 22, 2002 9:22 AM
> To: pgsql-jdbc(at)postgresql(dot)org
> Subject: [JDBC] Handling null values in char fields from JDBC
>
>
>
> I am running Postgresql 7.1.3 and using the 7.1-1.2 jar jdbc driver.
I
> noticed that when I used a ResultSet.getString("charfield") call to
> fetch null data from the char field I get a null pointer exception
> error. My question is two fold..
> 1) Is this normal behavior for the jdbc driver?
> 2) Is there a recommended way of trapping for a null value in a char
> field (besides just going into the db with psql and setting all null
> values to '')?
>
> I have looked thru two different Postgresql manuals but have not been
> able to find anything referring to null value handling at the jdbc
> level.
>
> If anyone can pt me in the right direction I
> would really appreciate it.
>
> Thanks!
> --
>
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