对不同的servlet使用一个会话属性

Question

我已经为用户创建了登录环境，我已经从数据库中检索了用户名和密码进行登录。并将用户名设置为会话中的字符串。现在我想对另一个servlet使用相同的用户名。在两个servlet中使用相同的字符串。如何为另一个servlet使用相同的会话属性。下面是我的代码。 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();
    }

}
}

我要在此处使用会话值userid的profile servlet

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

在第一个servlet您将像session那样存储值。

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

同样，您需要从第二个servlet session中检索这些值，例如

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

现在，使用此userid在第二个变量servlet 。

HttpSession＃getAttribute（）

像这样准备preparestatement以避免SQL注入

会议

Answer 2

首先像这样将值存储在会话中

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

这样访问会话值

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

Answer 3

在“配置文件” Servlet中，您可以使用以下方法查找HttpSession。

HttpSession httpSession = request.getSession（false）;

如果在登录servlet之前调用了概要文件servlet，则“ false”将确保您不会创建新的会话。

一旦获得会话，就可以读取之前存储的属性值。

Answer 4

我不能使用什么意思？

如果您想在其他servlet中使用存储的值，请执行此HttpSession session = request.getSession（）;。 字符串user = session.getAttribute（“ userid”）;

如果您想使用相同的key（“ userid”）为其设置新值，则无法执行此操作，因为即使创建新的会话对象，会话范围在每个地方都是通用的，所以您在后台使用同一会话，因此应选择新的字符串。

Answer 5

尝试这个 ....

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();
    }

}

}

sessionmanager的代码

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;
        }
    }
}

用于更改用户名或访问它的使用

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