Question

如果用户登录无效，我正在尝试在index.jsp页面中显示错误消息。

这是我的servlet代码：

if( passwordService.authenticate(password, attemptedPassword, salt)){


        User user = LogicFacade.login(email, password);

        HttpSession session = request.getSession();
        session.setAttribute("user", user);
        session.setAttribute("role", user.getRole());

        return user.getRole() + "page";  // i return the name of the jsp page, to get to the next jsp page

    }else{

    //here I make the error message I want to show
        String errorMessage ="The retrived password or username did not match";
        request.setAttribute("errorMessage", errorMessage );
           RequestDispatcher rd = request.getRequestDispatcher("/index.jsp");
                rd.forward(request, response);  
    }

}       catch (SQLException | NoSuchAlgorithmException | InvalidKeySpecException | ServletException | IOException ex) {
        Logger.getLogger(Login.class.getName()).log(Level.SEVERE, null, ex);
    }
    return null;

}
}

这里我在jsp中显示它：

 <%
if(null!=request.getAttribute("errorMessage"))
{
    out.println(request.getAttribute("errorMessage"));
    out.println("<p> Error!! </p>");
    //ved godt det ikke er super smart at printe paragraph tags med ud
}

 %>

为什么信息没有显示？

Answer 1

尝试这可以解决您的问题

#include <bits/stdc++.h>

using namespace std;
std::map<unsigned long long,unsigned long long> F;
unsigned long long fib(unsigned long long n)
{
    if(n==-1) return 0; // Shifting index by 1
    if(n==0) return 1;
    if(n==1) return 1;
    if(F.find(n) != F.end()) return F[n]; // This seems to be the problem,
    else
    {
        if(n%2==0) //
        {
            F[n/2-1] = fib(n/2-1)%1000000007;
            F[n/2] = fib(n/2)%1000000007;
            return F[n] = (F[n/2-1]*F[n/2-1]+F[n/2]*F[n/2])%1000000007;
        }
        else
        {
            F[n/2] = fib(n/2)%1000000007;
            F[n/2+1] = fib(n/2+1)%1000000007;
            return F[n] = (F[n/2]*(2*F[n/2+1]-F[n/2]))%1000000007;
        }
    }
}
int main() {
    unsigned long long int broj; 
    cin >> broj; // input the number
    cout << fib(broj-1) << endl;
    return 0;
}

在jsp中显示错误登录消息

1 个答案: