Re: please help: PostgreSQL JDBC Pooling problem

Marcus,

I can't reproduce your problem. When I run the modifed version of your
test (changes made so that it compiles and runs standalone) I don't have
any errors. My test table has about 1000 rows in it and everything
works fine without any errors.

I am running the latest 7.3 build (109) against a 7.3.2 database using
the sun 1.4.1_01 jdk on Redhat8.

Is there something else I need to do to reproduce the problem?

thanks,
--Barry

Marcus Andree S. Magalhaes wrote:
> Dear list,
>
>
> I'm having a couple problems while implementing a JDBC Connection pool using
> Postgresql Jdbc3PoolingDataSource.
>
> I was able to reproduce the errors with a simple java program. I'll be
> grateful if someone could analyse this problem for a while...
>
> The class io_property is a local class using standard java Properties
> classes to load data from a simple text file. This is done when calling
> the io_property.startService() static method.
>
> If I run the program exactly as show below, it works wonderfully. However,
> when commenting the return line of openConnection and uncommenting the
> previous 3 lines as:
>
> this.loConnection = loPoolSource.getConnection();
> System.out.println("loConnection = " + this.loConnection);
> loStatement = this.loConnection.createStatement();
> System.out.println("Statement = " + loStatement);
> return loStatement;
> // return this.loConnection.createStatement();
>
> The JDBC Statement returned is null. That's the problem I'm facing with my
> main application...
>
> Why is this happening?? In which circumstances
> does Connection.createStatement() return null???
>
>
> My main application is a bit different... It uses threads and lots of SQL
> code. I have to return a Statement instead of a Connection for historical
> reasons...
>
>
> Any help is welcome. The source file follows...
>
>
> Marcus
>
> ===============================================================================
>
> public class con_database {
>
> static Jdbc3PoolingDataSource loPoolSource = null;
> private Connection loConnection = null;
>
> con_database() {
> io_property.startService();
> }
>
> private static void setPool() {
> // DataSource initialization
> System.out.println("setPool()");
> try {
> System.out.println("setting pool");
> // constructs a pool only when loPoolSource is not assigned.
> // this will prevent problems if the same pool is set more than
> // one time
> if (loPoolSource == null) {
> loPoolSource = new Jdbc3PoolingDataSource();
> // DataSource configuration.
> loPoolSource.setDataSourceName(io_property.DATABASE_POOL_DATA_SOURCE_NAME); //
> any name is valid here
> loPoolSource.setServerName(io_property.DATABASE_POOL_SERVER_NAME);
> loPoolSource.setPortNumber(io_property.DATABASE_POOL_SERVER_PORT);
> loPoolSource.setDatabaseName(io_property.DATABASE_POOL_DATABASE_NAME);
> loPoolSource.setUser(io_property.DATABASE_POOL_USER_NAME);
> loPoolSource.setPassword(io_property.DATABASE_POOL_PASSWORD);
> loPoolSource.setMaxConnections(io_property.DATABASE_POOL_MAXCONNECTIONS);
>
> } else {
> System.out.println("pool is set");
> return;
> }
> } catch (Exception loException) {
> // logger.logToFile(loException);
> loException.printStackTrace();
> }
>
> }
>
>
>
> public Statement openConnection() {
> Statement loStatement;
> System.out.println("opening con");
> try {
> // gets a connection from Pool
> this.loConnection = loPoolSource.getConnection();
> System.out.println("loConnection = " + this.loConnection);
> // loStatement = this.loConnection.createStatement();
> // System.out.println("Statement = " + loStatement);
> // return loStatement;
> return this.loConnection.createStatement();
>
> } catch (Exception loException) {
> loException.printStackTrace();
> }
>
> return null;
> }
>
> public void closeConnection() {
> System.out.println("closing con");
> try {
> if (this.loConnection != null) this.loConnection.close();
> } catch (Exception loException) {
> loException.printStackTrace();
> }
> }
>
>
> public static void main(String args[]) {
>
> Statement loStatement = null;
> con_database loPoolConnection = new con_database();
> loPoolConnection.setPool();
> loStatement = loPoolConnection.openConnection();
> ResultSet lors = null;
> try {
> lors = loStatement.executeQuery("select * from <tablename>");
> while (lors.next()) {
> System.out.println(lors.getString(1));
> }
> } catch (Exception e) {
> e.printStackTrace();
> }
> finally {
> try {
> lors.close();
> loStatement.close();
> loPoolConnection.closeConnection();
> } catch (Exception loException) {
> loException.printStackTrace();
> }
> }
>
> loPoolConnection = new con_database();
> loPoolConnection.setPool();
> loStatement = null;
> loStatement = loPoolConnection.openConnection();
> lors = null;
> try {
> lors = loStatement.executeQuery("select * from <table_name>");
> while (lors.next()) {
> System.out.println(lors.getString(2));
> }
> } catch (Exception e) {
> e.printStackTrace();
> }
> finally {
> try {
> lors.close();
> loStatement.close();
> loPoolConnection.closeConnection();
> } catch (Exception loException) {
> loException.printStackTrace();
> }
> }
> }
> }
>
>
>
>
>
>
>
>
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