kazabubu

public class PoolableRegisteredConnectionFactory extends PoolableConnectionFactory {
  private ConnectionRegister connectionRegister;
  
@Override
public Object makeObject() throws Exception {
  PoolableConnection conn = (PoolableConnection) super.makeObject();
  if (connectionRegister != null) {
    connectionRegister.register(conn);
  }
  return conn;

kazabubu

public class ClosingPoolableConnectionsDataSource extends BasicDataSource implements ConnectionRegister {

  private Set<PoolableConnection> connections = new HashSet<>();

  @Override
  public synchronized void register(Connection conn) {
    if (PoolableConnection.class.isAssignableFrom(conn.getClass())) {
      connections.add((PoolableConnection) conn);
    }
  }