Re: NullPointer error returned from ResultSet.java

Nagarajan,

If you submit a complete test case that demonstrates the problem I would
be willing to look into this. But there just isn't enough information
in what you have provided here to debug this. I don't even know the
exact error you are getting.

thanks,
--Barry

G.Nagarajan wrote:
> Hi,
> I am also getting the same error. In my case I am using a prepared
statement
> to create the resultset like
>
> PreparedStatemet stmt = "...";
>
> callerFunction()
> {
> createPreparedStatement();
> fun1();
> closePreparedStatement();
> }
> fun1()
> {
> Results rs = stmt.executeQuery();
>
> while (rs.next() )
> {
> fun1(); //recursive call
> }
> rs.close();
> }
>
> The null pointer exception is throws after three recursive calls. The
code
> at
> 113 is rows.size(). Perhaps it has something to do with caching? The
error
> doesn't come if I use normal statements.
>
> Regards,
> Nagarajan.
>
>
>
>>-----Original Message-----
>>From: pgsql-jdbc-owner(at)postgresql(dot)org
>>[mailto:pgsql-jdbc-owner(at)postgresql(dot)org]On Behalf Of Jeff Duffy
>>Sent: Monday, October 07, 2002 5:57 PM
>>To: pgsql-jdbc(at)postgresql(dot)org
>>Subject: [JDBC] NullPointer error returned from ResultSet.java
>>
>>
>>Greetings,
>>
>> I have a JSP page with a rather large scriptlet that uses multiple
nested
>>statements and ResultSets. Under very specific conditions I am
>>encountering
>>the following error:
>>
>>java.lang.NullPointerException
>> at org.postgresql.jdbc2.ResultSet.next(ResultSet.java:113)
>>
>>
>>Here's one pertinent snippet of my code:
>>( This code begins inside a while(rs.next()) loop for ResultSet rs,
>>using Statement stmt)
>>
>>
>>sql.append("AN SQL QUERY");
>>rs2 = stmt2.executeQuery(sql.toString());
>>
>>while(rs2.next()){
>> String courseId = rs2.getString(1);
>> String roleName = rs2.getString(2);
>>
>> rs3 = stmt3.executeQuery("SELECT nextval('assignment_id')");
>> rs3.next();
>> assignmentId = rs3.getString(1);
>>
>> sql.delete(0, sql.length());
>> sql.append("AN SQL QUERY");
>> stmt3.executeUpdate(sql.toString());
>>}
>>
>> Through debugging it appears that rs2 is throwing the error; the message
>>states the error is in method next(), but if I have only zero records or
>>only one record in rs2, there is no error. It's only when I have multiple
>>records that the error is thrown the second time round the while
>>loop, so I
>>suspect it may be thrown at the assignment of courseId.
>>
>> This error is reproduced given the same conditions (nested
>>ResultSets with
>>the innermost ResultSet executing an Update inside a
>>while(ResultSet.next())
>>loop. It almost seems that the call to rs3.executeUpdate() is
>>closing rs2,
>>but I cannot see why that would happen. This is occurring in at least six
>>different source files.
>>
>> If I create a new Vector and stuff the contents of rs2 into it, then
>>iterate over the vector and use rs3 as shown above, no error is thrown.
>>
>> Updating to the 7.3beta1 JDBC driver changes the error message to:
>>
>>javax.servlet.ServletException: postgresql.con.closed
>>
>> which is even more puzzling.
>>
>>
>> Notes about my coding style that may be relevant:
>>- I use one StringBuffer for all sql queries and clear it for
>>each new query
>>for efficiency. This hasn't ever caused problems elsewhere.
>>
>>- I predeclare all Statement and ResultSet objects at the
>>outermost block of
>>code (the 'top') like so:
>>
>>Statement stmt = conn.createStatement();
>>Statement stmt2 = conn.createStatement();
>>Statement stmt3 = conn.createStatement();
>>ResultSet rs, rs2, rs3;
>>
>>Other data:
>>
>>- The connections are obtained from a custom class that uses the jdbcpool
>>pool manager.
>>- I'm using the Sun JDK v1.4.0 for Linux (it happens on Win32 as well).
>>- The JDBC library is v7.2 (the pgjdbc2.jar binary download).
>>- PostgreSQL 7.2.1 on i686-pc-linux-gnu, compiled by GCC 2.96
>>
>> Any flashes of insight?
>>
>>Thanks
>>
>>Jeff Duffy
>>jeff(at)alanne(dot)com
>>
>>
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>
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