Pooling Datasource DBCP
Here's a simple example of how to use the PoolingDataSource. In this example, we'll construct the PoolingDataSource manually, just to show how the pieces fit together, but you could also configure it using an external conifguration file in OCL format (and eventually Digester).
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import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.Statement;
import java.sql.ResultSet;
import java.sql.SQLException;

//
// Here are the dbcp-specific classes.
// Note that they are only used in the setupDataSource
// method. In normal use, your classes interact
// only with the standard JDBC API
//
import org.apache.commons.pool.ObjectPool;
import org.apache.commons.pool.impl.GenericObjectPool;
import org.apache.commons.dbcp.ConnectionFactory;
import org.apache.commons.dbcp.PoolingDataSource;
import org.apache.commons.dbcp.PoolableConnectionFactory;
import org.apache.commons.dbcp.DriverManagerConnectionFactory;

//
// Note that this example is very similiar to the PoolingDriver
// example. In fact, you could use the same pool in both a
// PoolingDriver and a PoolingDataSource
//

//
// To compile this example, you'll want:
// * commons-pool-1.5.4.jar
// * commons-dbcp-1.2.2.jar
// * j2ee.jar (for the javax.sql classes)
// in your classpath.
//
// To run this example, you'll want:
// * commons-pool-1.5.4.jar
// * commons-dbcp-1.2.2.jar
// * j2ee.jar (for the javax.sql classes)
// * the classes for your (underlying) JDBC driver
// in your classpath.
//
// Invoke the class using two arguments:
// * the connect string for your underlying JDBC driver
// * the query you'd like to execute
// You'll also want to ensure your underlying JDBC driver
// is registered. You can use the "jdbc.drivers"
// property to do this.
//
// For example:
// java -Djdbc.drivers=oracle.jdbc.driver.OracleDriver
// -classpath commons-pool-1.5.4.jar:commons-dbcp-1.2.2.jar:j2ee.jar:oracle-jdbc.jar:.
// ManualPoolingDataSourceExample
// "jdbc:oracle:thin:scott/tiger@myhost:1521:mysid"
// "SELECT * FROM DUAL"
//
public class ManualPoolingDataSourceExample {

public static void main(String[] args) {
//
// First we load the underlying JDBC driver.
// You need this if you don't use the jdbc.drivers
// system property.
//
System.out.println("Loading underlying JDBC driver.");
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
System.out.println("Done.");

//
// Then, we set up the PoolingDataSource.
// Normally this would be handled auto-magically by
// an external configuration, but in this example we'll
// do it manually.
//
System.out.println("Setting up data source.");
DataSource dataSource = setupDataSource(args[0]);
System.out.println("Done.");

//
// Now, we can use JDBC DataSource as we normally would.
//
Connection conn = null;
Statement stmt = null;
ResultSet rset = null;

try {
System.out.println("Creating connection.");
conn = dataSource.getConnection();
System.out.println("Creating statement.");
stmt = conn.createStatement();
System.out.println("Executing statement.");
rset = stmt.executeQuery(args[1]);
System.out.println("Results:");
int numcols = rset.getMetaData().getColumnCount();
while(rset.next()) {
for(int i=1;i<=numcols;i++) {
System.out.print("t" + rset.getString(i));
}
System.out.println("");
}
} catch(SQLException e) {
e.printStackTrace();
} finally {
try { if (rset != null) rset.close(); } catch(Exception e) { }
try { if (stmt != null) stmt.close(); } catch(Exception e) { }
try { if (conn != null) conn.close(); } catch(Exception e) { }
}
}

public static DataSource setupDataSource(String connectURI) {
//
// First, we'll need a ObjectPool that serves as the
// actual pool of connections.
//
// We'll use a GenericObjectPool instance, although
// any ObjectPool implementation will suffice.
//
ObjectPool connectionPool = new GenericObjectPool(null);

//
// Next, we'll create a ConnectionFactory that the
// pool will use to create Connections.
// We'll use the DriverManagerConnectionFactory,
// using the connect string passed in the command line
// arguments.
//
ConnectionFactory connectionFactory = new DriverManagerConnectionFactory(connectURI,null);

//
// Now we'll create the PoolableConnectionFactory, which wraps
// the "real" Connections created by the ConnectionFactory with
// the classes that implement the pooling functionality.
//
PoolableConnectionFactory poolableConnectionFactory = new PoolableConnectionFactory(connectionFactory,connectionPool,null,null,false,true);

//
// Finally, we create the PoolingDriver itself,
// passing in the object pool we created.
//
PoolingDataSource dataSource = new PoolingDataSource(connectionPool);

return dataSource;
}
}