As this tutorial uses SQL Server, you need a SQL Server-compatible JDBC driver. Download a Microsoft JDBC SQL Server Type 4 driver using this link, and install it using the Install Instructions on the download page:
The name of the driver file is sqljdbc4[n].jar where n is a single digit and is appended to the filename for some versions of the driver. Be sure to take note of the location of this file after installing it.
To run your application, the Tomcat application server must find an SQL Server JDBC driver file in the Apache Tomcat installation lib subdirectory. To ensure that Tomcat finds the file there, copy the installed sqljdbc4[n].jar file to the lib subdirectory of your Apache Tomcat installation.