Establish Connection Using Connection Pool And Retrieve Username

I have created a JSP page, on click of a particular button, the control moves to the servlet "TestServlet".

This is the code under TestServlet:

import java.io.IOException;
import java.io.PrintWriter;
import java.security.Principal;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;

[Code]...

Now, I have got a comment saying I should get the database connection from connection pool. And one more issue is that I have used the function System.getProperty("user.name") to get the username which i have logged in. But this code will be run on Unix which will not support this function. Any function where I can get the windows username. There is a function getUserPrincipal(), but this function returns a NULL. How to resolve this.