Microsoft SQL Server 2019 (RTM-CU18) (KB5017593) - 15.0.4261.1 (X64) 
	Sep 12 2022 15:07:06 
	Copyright (C) 2019 Microsoft Corporation
	Developer Edition (64-bit) on Windows 10 Pro 10.0 <X64> (Build 19045: )

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.sql.PooledConnection;

public class SQLConnectionPool {

	 final private ReentrantLock _connLock = new ReentrantLock();
	 final private Map _userToConnectionsMap = new ConcurrentHashMap();
	 static String tableName = "batchTest";
	/**
	 * Crate a new connection
	 * 
	 * @return the new created connection
	 * @throws SQLException When fail to create a new connection.
	 */
	private Connection createNewConnection(final String username, final String password) throws SQLException {

		com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource msDs = new com.microsoft.sqlserver.jdbc.SQLServerConnectionPoolDataSource();
		msDs.setUser(username);
		msDs.setApplicationName("SQL Server Duplicate Row");
		msDs.setPassword(password);
		msDs.setServerName("<>");
		msDs.setPortNumber(0);
		msDs.setDatabaseName("<>");
		msDs.setInstanceName("<>");
		msDs.setEncrypt("false");
		msDs.setDisableStatementPooling(false);
		msDs.setStatementPoolingCacheSize(20);
		msDs.setServerPreparedStatementDiscardThreshold(20);
		msDs.setSendTemporalDataTypesAsStringForBulkCopy(false);
		// ... create the ACTUAL new connection...
		PooledConnection actual = msDs.getPooledConnection(username, password);
		// ... cache it...
		Collection conns = (Collection) _userToConnectionsMap.get(username);
		if (conns == null || conns.isEmpty()) {
			conns = new CopyOnWriteArrayList();
			_userToConnectionsMap.put(username, conns);
		}
		
		conns.add(actual);
		return actual.getConnection();
	}

	final public Connection getConnection(final String username, final String password)
			throws SQLException, InterruptedException {

		if (username == null) {
			throw new NullPointerException("The username cannot be null.");
		}
		if (password == null) {
			throw new NullPointerException("The password cannot be null.");
		}

		// Acquire a lock...
		_connLock.lock();
		// Declare the connection to be returned...
		Connection conn = null;
		try {

			conn = getAvailableConnection(username);
			// If none found...
			if (conn == null) {
				conn = createNewConnection(username, password);
			}
//	           
		} finally {
			// Ensure that the lock is released...
			_connLock.unlock();
		}
		// Return the connection...
		return conn;
	}

	private Connection getAvailableConnection(final String username) throws SQLException {
		// Get the connections for the specified user...
		Collection conns = (Collection) _userToConnectionsMap.get(username);
		// If none found, then NO connections are available...
		if (conns == null || conns.isEmpty()) {
			return null;
		}
		// ... otherwise, check to see if any of the connections are available...
		boolean isAvailable = false;
		final Iterator iterator = conns.iterator();
		PooledConnection pconn = null;
		while (iterator.hasNext()) {			
			pconn = (PooledConnection) iterator.next();

			return pconn.getConnection();
			// Is this connection available? ignore this check for this sample test
			
		}
		return null;
	}

	public static void main(String[] args) throws SQLException, ClassNotFoundException, InterruptedException {

		Logger logger = Logger.getLogger("com.microsoft.sqlserver.jdbc.Statement");
		logger.setLevel(Level.FINER);
		Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");

		SQLConnectionPool pool = new SQLConnectionPool();

		try {
		
			Connection conn = pool.getConnection("<>", "<>");
			try (Statement stmt = conn.createStatement();) {

				String dropSql = "if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[" + tableName
						+ "]') and OBJECTPROPERTY(id, N'IsUserTable') = 1) DROP TABLE [" + tableName + "]";
				stmt.execute(dropSql);

				String createSql = "create table " + tableName + " (c1 int, c2 varchar(20))";
				stmt.execute(createSql);
			}
			for (int j = 0; j < 5; j++) {

				conn = pool.getConnection("<>", "<>");
				conn.setAutoCommit(false);
				try (PreparedStatement pstmt = conn.prepareStatement("insert into " + tableName + " values (?, ?)");) {
					for (int i = 0; i < 3; i++) {
						pstmt.setInt(1, i);
						pstmt.setString(2, "test" + i);
						pstmt.addBatch();
					}

					long start = System.currentTimeMillis();
					pstmt.executeBatch();
					conn.commit();
					long end = System.currentTimeMillis();

					System.out.println("Finished. Time taken : " + (end - start) + " milliseconds.");
				}
				conn.close();
			}
		} finally {
			// nothing for this test
		}

	}
}