java - 如何在登录页面中传递已保存在我的数据库中的用户名和密码参数？

Question

+----------+-------------+------+-----+---------+-------+
| Field    | Type        | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+-------+
| name     | varchar(30) | YES  |     | NULL    |       |
| password | varchar(30) | YES  |     | NULL    |       |
| mno      | varchar(30) | YES  |     | NULL    |       |
| eid      | varchar(30) | YES  |     | NULL    |       |
| city     | varchar(30) | YES  |     | NULL    |       |
| pin      | varchar(30) | YES  |     | NULL    |       |
| status   | varchar(30) | YES  |     | NULL    |       |
| cname    | varchar(30) | YES  |     | NULL    |       |
| aincome  | varchar(30) | YES  |     | NULL    |       | 
+----------+-------------+------+-----+---------+-------+

这是我的表描述..我已在该表中注册了一些用户。我想以特定用户身份从该数据库登录。我想在jsp和servlet编码中实现

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
public class loginservlet extends HttpServlet
{
public void doGet(HttpServletRequest req,HttpServletResponse res) throws ServletException,IOException
{

        doPost(req,res);

}
public void doPost(HttpServletRequest req,HttpServletResponse res) throws    ServletException,IOException
    {
res.setContentType("text/html");
PrintWriter pw=res.getWriter();
    String s1=req.getParameter("name");
    String s2=req.getParameter("password");
    try
    {

         //Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
         //Connection con=DriverManager.getConnection("jdbc:odbc:cinfo");
        Class.forName("com.mysql.jdbc.Driver"); 
        Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/cinfo","root","root");
        Statement st=con.createStatement();
        //string query="select * from newuser where  name='"+name+"',password='"+password"'";
  //ResultSet rs=st.executeQuery("select * from newuser where name='"+s1+"'");
            //,password='"+password"'");

        if(s1.equals("name") || s2.equals("password"))
        {

                RequestDispatcher rd=req.getRequestDispatcher("index.jsp");
                    rd.forward(req,res);
        }
    else
        {
        //req.getAttirbute("You are not a valid customer");
        pw.println("You are not a valid customer");
        }
    }
    catch(Exception e)
    {
        pw.println(e);
    }
    }
}

Answer 1

您的 Servlet 可能看起来像这样(Java 7 语法) - 未经测试。

想法是使用 PreparedStatement 查找并输入匹配的用户名和密码(顺便说一句。不要将纯文本密码存储在数据库)。

如果找不到该条目 (resp.first() == false) 将用户重定向到登录 (login.jsp) 页面 - 可能会显示一些错误消息。

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class Loginservlet extends HttpServlet {


public void doPost(HttpServletRequest req, HttpServletResponse res)
        throws ServletException, IOException {

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

    try (
            Connection con = DriverManager.getConnection(
            "jdbc:mysql://localhost:3306/cinfo", "root", "root");
            PreparedStatement st = con.prepareStatement("select name from newuser where name = ? and password = ?");

        )
        {
            st.setString(1, name);
            st.setString(2, password);

            try (
                    ResultSet result = st.executeQuery();
                )
            {

                if (result.first()) {

                    RequestDispatcher rd = req.getRequestDispatcher("index.jsp");
                    rd.forward(req, res);

                } else {
                    // username or password wrong - back to the login page.
                    RequestDispatcher rd = req.getRequestDispatcher("longin.jsp");
                    rd.forward(req, res);
                }

        }
    } catch (Exception e) {
        throw new ServletException("Internal Server Error", e);
    }
}
}