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@postgresql.org
 >>[mailto:pgsql-jdbc-owner@postgresql.org]On Behalf Of Jeff Duffy
 >>Sent: Monday, October 07, 2002 5:57 PM
 >>To: pgsql-jdbc@postgresql.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@alanne.com
 >>
 >>
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 >
 >
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