HTTP状态500 - 在第11行处理JSP页面/checkusername.jsp时发生异常

Question

我的代码是

<% 
 String sn=request.getParameter("ver");
 Class.forName("com.mysql.jdbc.Driver");
 Connection con =DriverManager.getConnection("jdbc:mysql://localhost:3306/publiccloud","root","root");
 Statement st=con.createStatement();
 ResultSet rs = st.executeQuery("select * from reg where Username='"+sn+"'");  // this is for name