对不同的servlet使用一个会话属性

Question

I've made a login environment for a user, i've retrieved username and password from database for login.And set user name as a string in a session.now i want to use same user name for another servlet.But i can't use the same string in two servlet.How can i use the same session attribute for another servlet.Below is my code. loginservlet

import java.io.IOException;
import java.io.PrintWriter;
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 java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
@WebServlet(urlPatterns = {"/LoginServlet"})
public class LoginServlet extends HttpServlet {

String userid, pwd;

protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    Connection connection = null;
    Statement statement = null;

    userid = request.getParameter("uname");
    pwd = request.getParameter("pass");
    try {
        dbconnector dbc = new dbconnector();
        connection = dbc.Open();
        PreparedStatement ps = connection.prepareStatement("select * from member where uname='" + userid + "' and pass='" + pwd + "'");

        ResultSet rs = ps.executeQuery();
        if (rs.next()) {
            HttpSession session = request.getSession();
            session.setAttribute("userid", userid);
            //out.println("welcome " + userid);
            //out.println("<a href='logout.jsp'>Log out</a>");
            response.sendRedirect("success.jsp");
        } else {

            request.setAttribute("errorMessage", "Invalid user or password");
            RequestDispatcher rd = getServletContext().getRequestDispatcher("/index.jsp");
            rd.include(request, response);

        }

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

}
}

profile servlet here i want to use the session value userid

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;
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;


@WebServlet(urlPatterns = {"/usesesvaluegetdbdata"})
public class usesesvaluegetdbdata extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
      Connection connection = null;
    Statement statement = null;
    String userid;

    try {
        dbconnector dbc = new dbconnector();
        connection = dbc.Open();
        PreparedStatement ps = connection.prepareStatement("select eid,ename from member where uname='" + userid + "' and pass='" + pwd + "'");



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

}

Answer 1

In first servlet you are storing value(s) in session like.

HttpSession session = request.getSession();
session.setAttribute("userid", userid);

In the same you need to retrieve those values from session in second servlet like

HttpSession session = request.getSession();
String userid=(String)session.getAttribute("userid");//cast to String, default its Object

Now use this userid variable in the second servlet .

HttpSession#getAttribute()

preparestatement follow like this to avoid sql injection

session

Answer 2

first store the value in session like this

HttpSession session = request.getSession();
session.setAttribute("userid", userid);

Access the session value like this

  HttpSession session=request.getSession();
  String username = session.getAttribute("userid").toString() ;

Answer 3

In the 'profile' servlet you can lookup HttpSession using following method.

HttpSession httpSession = request.getSession( false );

'false' will make sure you don't create new session in case profile servlet is called before login servlet.

Once you get the session you can read the value of attribute stored earlier.

Answer 4

What do u meant by i can't use ?

if u want to use stored value in other servlet do this HttpSession session = request.getSession(); String user= session.getAttribute("userid");

if u want to use same key("userid") to set new value into it you cannot do that because session scope is common everywhere even if you create new session object you are using same session in background so you should choose new string.

Answer 5

try this ....

import java.io.IOException;
import java.io.PrintWriter;
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 java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;

@WebServlet(urlPatterns = {"/LoginServlet"})
public class LoginServlet extends HttpServlet {

    String userid, pwd;

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        Connection connection = null;
        Statement statement = null;

        userid = request.getParameter("uname");
        pwd = request.getParameter("pass");

    try {
        HttpSession session = request.getSession(true);//true if first session else use false
        if (SessionManager.checkUserSession(session)) {
            dbconnector dbc = new dbconnector();
            connection = dbc.Open();
            PreparedStatement ps = connection.prepareStatement("select * from member where uname='" + userid + "' and pass='" + pwd + "'");

            ResultSet rs = ps.executeQuery();
            if (rs.next()) {

                session.setAttribute("userid", userid);
                //out.println("welcome " + userid);
                //out.println("<a href='logout.jsp'>Log out</a>");
                response.sendRedirect("success.jsp");
            } else {

                request.setAttribute("errorMessage", "Invalid user or password");
                RequestDispatcher rd = getServletContext().getRequestDispatcher("/index.jsp");
                rd.include(request, response);

            }
        }
        request.setAttribute("statuscode", "HTTP_STATUS_INVALID_SESSION");
    } catch (Exception e) {
        e.printStackTrace();
    }

}

}

code for sessionmanager

public class SessionManager {

    public static boolean checkUserSession(HttpSession loginSession) {
        if ((loginSession == null) || (loginSession.toString().isEmpty())) {
            return false;
        } else if (loginSession.isNew()) {
            return false;
        } else {
            return true;
        }
    }
}

for changing the user name or accessing it use

HttpSession session = request.getSession();
String userid=(String)session.getAttribute("userid");