Servlet转发到jsp空白页面

Question

这是我用来通过java中的servlet页面连接到MySQL数据库的代码，我试图将用户从注册页面转发到感谢页面或注册错误页面

// Get parameters from the request
        String uname = request.getParameter("uname");
        String pass = request.getParameter("pass");
        String email = request.getParameter("email");
        String country = request.getParameter("country");
        // Check Mandatory Fields
        if(pass == null||uname == null||email == null){
            RequestDispatcher dispatcher =
            request.getRequestDispatcher("regerror.jsp");
            dispatcher.forward(request, response);

        }

        else{
        //Establish connection to Database
        Connection con = null;
        Statement stmt = null;
        String databaseURL = "jdbc:mysql://localhost:3306/account";
        String driverName = "com.mysql.jdbc.Driver";
        String user = "root";
        String password = "root";

        try {
            Class.forName(driverName).newInstance();
            con = DriverManager.getConnection(databaseURL, user, password);
            stmt = con.createStatement();
        } catch (Exception e) {
            System.out.println("ERROR Connecting to DB: " + e);
            return;
        }

        //Insert SQL statement
        String insertStmt = "insert into account values ("
                + "'" + uname + "', "
                + "'" + pass + "', "
                + "'" + email + "',"
                + "'" + country + "'"
                + ")";
        // Execute the insert statement
        try {
            stmt.executeUpdate(insertStmt);
        } catch (Exception e) {
            System.out.println("ERROR: Insert into DB: " + e);
            return;
        }
        //Close the database connection


        try {
            stmt.close();
            con.close();
        } catch (SQLException e) {
            System.out.println("ERROR: closing DB connection: " + e);
        }

    }
        RequestDispatcher dispatcher3 =
            request.getRequestDispatcher("thanks.jsp");
            dispatcher3.forward(request, response);
}

当您单击“提交”按钮时，会有一个注册表单页面将您带到此servlet，但是当您单击“提交”按钮时，它只会显示一个空白页面，而不是将我带到＆＃34; thanks.jsp＆＃ 34;或者＆＃34; regerror.jsp＆＃34;页。当我删除if，else语句并在页面开头放置一个请求调度程序时，代码似乎有效，所以我知道寄存器jsp将你带到这个servlet。