如何从servlet重定向到jsp页面

Question

well I have a jsp page with a login form, i'm using a servlet, if the username and password are correct the servlet redirects the user to another page else it redirects him to the login page again

when i log in with a correct username and password i'm redirected perfectly to reservation.jsp but when i put a wrong username or password in the form when i click on the submit button the page became blank

here is the servlet

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.*;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.mysql.jdbc.PreparedStatement;

/**
 * Servlet implementation class LogServlet
 */
@WebServlet("/LogServlet")
public class LogServlet extends HttpServlet {
private static final long serialVersionUID = 1L;




public LogServlet() {
    super();

}



protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    response.setContentType("text/html");


    String name=request.getParameter("name");
    String password=request.getParameter("password");

    PreparedStatement ps = null;
    ResultSet rs = null;

    try {
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/log",
                "root","");
        ps = (PreparedStatement) conn.prepareStatement("select nom_client,username,password from client where username = ? and password = ?");

        ps.setString(1, name);
        ps.setString(2, password);
        rs=ps.executeQuery();



    try {
        while(rs.next()){
        if(password.equals(rs.getString("password")) && name.equals(rs.getString("username"))){

        HttpSession session=request.getSession();
        session.setAttribute("name",name);
        PrintWriter out=response.getWriter();
        request.getRequestDispatcher("reservation.jsp").include(request, response);
        }
        else{
            response.sendRedirect("/login.jsp");

        }}
    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();

    }
    System.out.close();


    }
    catch(Exception e){e.printStackTrace();}


}
}

Answer 1

use request.getContextPath() , It will redirect you to login page.

response.sendRedirect(request.getContextPath()+"/login.jsp");

and if you are reaching to your login page in that case, pass request and response objects to your jsp page.

request.getRequestDispatcher(request.getContextPath()+"/login.jsp").forward(request,response);

Answer 2

use this.

request.getRequestDispatcher("/login.jsp").forward(request,response);

As you have used

request.getRequestDispatcher("reservation.jsp").include(request, response); 

to forward after successful login and as it is working, why not forwarding after failed also in this way .?

Which mean to use

request.getRequestDispatcher("/login.jsp").include(request, response); 

Answer 3

request.getRequestDispatcher("login.jsp").include(request, response);

Have u tried above code in else part ? I think it should work

Answer 4

Problem is response.sendRedirect(...) does not prepend the context path where the resource (jsp) is bundled. Try using request.getRequestDispatcher(...) in both cases.

Answer 5

The problem could be here:

response.sendRedirect("/login.jsp");

This means that in the location header of the redirect response you will have:

http://localhost:8080/login.jsp

If you change it to:

response.sendRedirect("login.jsp");

than its relative to your webabb context path:

http://localhost:8080/app/login.jsp

Try with firebug or similar and trace down request/response you should find out quickly. And be sure jsp files are were expected in the hierarchy.

Hope this helps

Answer 6

Rather than giving response.sendRedirect("\\login.jsp"); use response.sendRedirect("/yourprojectname/"); and in welcome file in web.xml set login.jsp as welcome file.

Answer 7

Add this

response.sendRedirect("/yourprojectname/");

and set login.jsp as welcome file in web.xml

Answer 8

来自数据库的响应为空，因此我不得不将该案例添加到类中（通过if/else条件）。