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Postgresql JDBC errors
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* Postgresql JDBC errors
@ 2000-04-18 04:16 Nick Rathke <render@uswest.net>
  0 siblings, 0 replies; 2+ messages in thread

From: Nick Rathke @ 2000-04-18 04:16 UTC (permalink / raw)
  To: pgsql-interfaces

I an using Postgresql-6.5.3 with jdbc6.5-1.2 and jdk1.2.2 on redhat
linux 6.2 . I
have tried to check the jdbc link using JDBCtest.java. Here is the info.

my classpath is

CLASSPATH=/lib/jdbc6.5-1.1.jar

JDBCtest.java

/*
    This file is part of the tutorial in Chapter 3 of "Getting Started
with Enhydra".
    It is not meant to be used in any other context.

    Simple program to test JDBC connectivity.  Assumes you have created
and populated
    a table called LE_TUTORIAL_DISCS in your database.
    Edit the connection string in the call to
DriverManager.getConnection()/

*/

import java.sql.*;
public class JDBCTest {
 public static void main( String[] args ) {
  Connection con  = null;
  Statement  stmt = null;
  ResultSet  rs   = null;
// Load the driver, get a connection, create statement, run query, and
print.
  try {
   Class.forName("postgresql.Driver");
   // Replace parameters below your database connection string,
username, and password
   con = DriverManager.getConnection("jdbc:postgresql:dbtest"
,"appserver", "appserver" );
   stmt = con.createStatement();
   rs = stmt.executeQuery("SELECT * FROM LE_TUTORIAL_DISCS");
   rs.next();
   System.out.println("Title = " + rs.getString("title") + " -- Artist =

" + rs.getString("artist"));
  }
  catch(ClassNotFoundException e) {
   System.err.println("Couldn't load the driver: " + e.getMessage());
  }
  catch(SQLException e) {
   System.err.println("SQLException caught: " + e.getMessage());
  }
 }
}

which gives me the errors:

Exception in thread "main" java.lang.NullPointerException:
                                    at
postgresql.jdbc2.ResultSet.getString(ResultSet.java:148)
                                    at
postgresql.jdbc2.ResultSet.getString(ResultSet.java:531)
                                    at JDBCTest.main(JDBCTest.java:25)

I don't know enough about Java or databases to make any sense of this.
Any help would be great.

Nick Rathke







^ permalink  raw  reply  [nested|flat] 2+ messages in thread

* RE: Postgresql JDBC errors
@ 2000-04-18 07:19 Peter Mount <petermount@it.maidstone.gov.uk>
  0 siblings, 0 replies; 2+ messages in thread

From: Peter Mount @ 2000-04-18 07:19 UTC (permalink / raw)
  To: 'Nick Rathke' <render@uswest.net>; pgsql-interfaces

Which line is line 25 exactly?

Technically after the executeQuery(), rs may be null, so you should wrap
the next two lines in an if statement. ie:

rs = stmt.executeQuery("SELECT * FROM LE_TUTORIAL_DISCS");
if(rs) {
   rs.next();
   System.out.println("Title = " + rs.getString("title") + " -- Artist =
" + rs.getString("artist"));
   rs.close(); // note to close the ResultSet
}

Peter

-- 
Peter Mount
Enterprise Support
Maidstone Borough Council
Any views stated are my own, and not those of Maidstone Borough Council.



-----Original Message-----
From: Nick Rathke [mailto:render@uswest.net]
Sent: Tuesday, April 18, 2000 5:17 AM
To: pgsql-interfaces@postgresql.org
Subject: [INTERFACES] Postgresql JDBC errors


I an using Postgresql-6.5.3 with jdbc6.5-1.2 and jdk1.2.2 on redhat
linux 6.2 . I
have tried to check the jdbc link using JDBCtest.java. Here is the info.

my classpath is

CLASSPATH=/lib/jdbc6.5-1.1.jar

JDBCtest.java

/*
    This file is part of the tutorial in Chapter 3 of "Getting Started
with Enhydra".
    It is not meant to be used in any other context.

    Simple program to test JDBC connectivity.  Assumes you have created
and populated
    a table called LE_TUTORIAL_DISCS in your database.
    Edit the connection string in the call to
DriverManager.getConnection()/

*/

import java.sql.*;
public class JDBCTest {
 public static void main( String[] args ) {
  Connection con  = null;
  Statement  stmt = null;
  ResultSet  rs   = null;
// Load the driver, get a connection, create statement, run query, and
print.
  try {
   Class.forName("postgresql.Driver");
   // Replace parameters below your database connection string,
username, and password
   con = DriverManager.getConnection("jdbc:postgresql:dbtest"
,"appserver", "appserver" );
   stmt = con.createStatement();
   rs = stmt.executeQuery("SELECT * FROM LE_TUTORIAL_DISCS");
   rs.next();
   System.out.println("Title = " + rs.getString("title") + " -- Artist =

" + rs.getString("artist"));
  }
  catch(ClassNotFoundException e) {
   System.err.println("Couldn't load the driver: " + e.getMessage());
  }
  catch(SQLException e) {
   System.err.println("SQLException caught: " + e.getMessage());
  }
 }
}

which gives me the errors:

Exception in thread "main" java.lang.NullPointerException:
                                    at
postgresql.jdbc2.ResultSet.getString(ResultSet.java:148)
                                    at
postgresql.jdbc2.ResultSet.getString(ResultSet.java:531)
                                    at JDBCTest.main(JDBCTest.java:25)

I don't know enough about Java or databases to make any sense of this.
Any help would be great.

Nick Rathke






^ permalink  raw  reply  [nested|flat] 2+ messages in thread

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