Обсуждение: exception while upgrading driver

Hi
   i have the following code running without any errors with postgres 7.4.2.
driver.



String qry="select MAX(num) from (select
to_number((substr(acr_id,4)),'9999') as num from aircraft where acr_id  like
'ACR%'  group by acr_id) as num ";  // order by num desc";

try{
  ResultSet rs=Data.getResultSet(qry);
  while(rs.next())
   {
        try{
            acrmax=Integer.parseInt(rs.getString(1))+1;
           }catch(NumberFormatException ne){acrmax=0;}
   }
  }
  catch(SQLException ex) { System.err.println("for rs1 err
"+ex.getMessage());
        }



I changed the driver to postgres 8.0.1.  Strangely now, the above code gives
the exception "The resultset is closed". Please help.

regards,

Sathya

On Tue, 7 Jun 2005, Sathyajith G wrote:

>    i have the following code running without any errors with postgres 7.4.2.
> driver.
>
> String qry="select ...;
>
> try{
>   ResultSet rs=Data.getResultSet(qry);
>   while(rs.next())
>
> I changed the driver to postgres 8.0.1.  Strangely now, the above code gives
> the exception "The resultset is closed". Please help.
>

I suspect your Data.getResultSet() method looks something like this:


Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql);
stmt.close();
return rs;

This is not a legal thing to do, closing the Statement also closes the
ResultSet that was created by it.  The 7.4 driver did not correctly check
this, but the 8.0 version does.  You most postpone the Statement close
until you are done with the ResultSet.

Kris Jurka

>>
>
> On Tue, 7 Jun 2005, Sathyajith G wrote:
>
> >    i have the following code running without any errors with postgres
> 7.4.2.
> > driver.
> >
> > String qry="select ...;
> >
> > try{
> >   ResultSet rs=Data.getResultSet(qry);
> >   while(rs.next())
> >
> > I changed the driver to postgres 8.0.1.  Strangely now, the above code
> gives
> > the exception "The resultset is closed". Please help.
> >
>
> I suspect your Data.getResultSet() method looks something like this:
>
>
> Statement stmt = conn.createStatement();
> ResultSet rs = stmt.executeQuery(sql);
> stmt.close();
> return rs;
>
> This is not a legal thing to do, closing the Statement also closes the
> ResultSet that was created by it.  The 7.4 driver did not correctly check
> this, but the 8.0 version does.  You most postpone the Statement close
> until you are done with the ResultSet.
>
> Kris Jurka
>

-------------------------------------------------------------------

i am not closing the statement anywhere. this is how Data.getResultSet()
looks like:

public static  ResultSet getResultSet(String sql)
     {
       ResultSet rs;
        try{
             rs=stmt.executeQuery(sql);
            }catch(Exception e)
                   {System.err.println("error");
                    rs=null;
                    }
            return rs;
     }


Sathyajith Gopi

Sathyajith G wrote:

>   ResultSet rs=Data.getResultSet(qry);

> I changed the driver to postgres 8.0.1.  Strangely now, the above code gives
> the exception "The resultset is closed". Please help.

Perhapse Data.getResultSet() closes the Statement used to execute the
query before returning -- closing the Statement also closes the ResultSet.

It's hard to diagnose further without seeing all the code that's running.

-O

Sathyajith G wrote:

> public static  ResultSet getResultSet(String sql)
>      {
>        ResultSet rs;
>         try{
>              rs=stmt.executeQuery(sql);
>             }catch(Exception e)
>                    {System.err.println("error");
>                     rs=null;
>                     }
>             return rs;
>      }

Where does 'stmt' come from?

Can we see a compilable testcase that shows the problem? Code fragments
really aren't too useful for this sort of problem -- we need to see
everything involved with talking to the JDBC driver. e.g. perhaps the
lifetime of your Statement is not what you think it is and it's getting
GCed unexpectedly.. but I can't say for sure without seeing the actual
code you're running.

-O