无法使用java连接到MS数据库

Question

尝试打开与数据库的连接时，它无法给我一个NullPointerException。当它尝试获取con = DriverManager.getConnection（url）上的连接时会发生这种情况;线。它从这一行到catch异常。什么是正确的方法？

    public void openDatabase () {
    url = "jdbc:odbc:student";              

    try{                                    
        con = DriverManager.getConnection(url);
        stmt = con.createStatement();
        txtOutput.setText("Database " + url + " is connected\n");
    }
    catch (Exception e) {
        txtOutput.setText("Problems connecting to " + url + "\n");
    }
}