Kohei Nozaki's blog 

<Resource name="jdbc/derby" auth="Container"
		  driverClassName="org.apache.derby.jdbc.EmbeddedDriver"
		  username="sa" password="sa"
		  type="javax.sql.DataSource"
		  url="jdbc:derby:/Users/kyle/tmp/sampledb;create=true"/>

<Listener className="org.nailedtothex.derby.DerbyShutdownLifecycleListener" />

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"
         version="3.1">
    <resource-ref>
        <res-ref-name>jdbc/derby</res-ref-name>
        <res-type>javax.sql.DataSource</res-type>
        <res-auth>Container</res-auth>
    </resource-ref>
</web-app>

@WebServlet(urlPatterns = "/")
public class TestServlet extends HttpServlet {

    private Context context;
    private DataSource dataSource;

    @Override
    public void init() throws ServletException {
        try {
            context = new InitialContext();
            dataSource = (DataSource) context.lookup("java:comp/env/jdbc/derby");
        } catch (NamingException e) {
            throw new ServletException(e);
        }
    }

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        try (Connection cn = dataSource.getConnection();
             Statement st = cn.createStatement();
             ResultSet rs = st.executeQuery("SELECT CURRENT_TIMESTAMP FROM SYSIBM.SYSDUMMY1")) {
            while (rs.next()) {
                resp.getWriter().write(rs.getTimestamp(1).toString());
            }
        } catch (SQLException e) {
            throw new ServletException(e);
        }
    }

    @Override
    public void destroy() {
        if (context != null) {
            try {
                context.close();
            } catch (NamingException e) {
                // no-op
            }
        }
    }
}