when running my servlet and when i have make resource in servere.xml
i get this message:

javax.servlet.ServletException: Cannot create JDBC driver of class '' for connect URL 'null'
ConnectToDB.doPost(ConnectToDB.java:55)
ConnectToDB.doGet(ConnectToDB.java:30)
javax.servlet.http.HttpServlet.service(HttpServlet .java:743)
javax.servlet.http.HttpServlet.service(HttpServlet .java:856)

connectDB is my servlet

Please help if you have any idea