Servlet+JDBC实现登陆功能的小例子(带验证码)

案例需求：访问带有验证码的登录页面login.jsp用户输入用户名，密码以及验证码。如果用户名和密码输入有误，跳转登录页面，提示:用户名或密码错误如果验证码输入有误，跳转登录页面，提示：验证码错误如果全部输入正确，则跳转到主页success.jsp，显示：用户名,欢迎您分析

步骤

文件树展示

1.配置文件和jar包在上个案例均有配置过，需要改的有：User类新增验证码成员变量，数据库增加了一个验证码字段（无用，只是为了UserDao包把查找到的数据值导入到User类不出错）。

2.登陆界面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
  <title>login</title>
  <script>
    window.onload = function(){
      document.getElementById("img").onclick = function(){
        this.src="/CaS/checkCodepic?time="+new Date().getTime();
      }
    }
  </script>
  <style>
    div{
      color: red;
    }
  </style>
</head>
<body>

  <form action="/CaS/loginServlet" method="post">
    <table>
      <tr>
        <td>用户名</td>
        <td><input type="text" name="username"></td>
      </tr>
      <tr>
        <td>密码</td>
        <td><input type="password" name="password"></td>
      </tr>
      <tr>
        <td>验证码</td>
        <td><input type="text" name="checkCode"></td>
      </tr>
      <tr>
        <td colspan="2"><img id="img" src="/CaS/checkCodepic"></td>
      </tr>
      <tr>
        <td colspan="2"><input type="submit" value="登录"></td>
      </tr>
    </table>


  </form>


  <div><%=request.getAttribute("cc_error") == null ? "" : request.getAttribute("cc_error")%></div>
  <div><%=request.getAttribute("login_error") == null ? "" : request.getAttribute("login_error") %></div>

</body>
</html>

3.验证码，画了个验证码，每次都把随机数加入session中以便进行对比

package Test;

import javax.imageio.ImageIO;
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.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

@WebServlet("/checkCodepic")
public class CheckCodepic extends HttpServlet {
  @Override
  protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    int width=100;
    int height=50;
    //创建图片对象
    BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);

    //美化图片
    //创建画笔
    Graphics g = image.getGraphics();
    //画笔颜色
    g.setColor(Color.pink);
    //画个矩形，填充为粉红色
    g.fillRect(0,0,width,height);
    //给矩形加边框
    g.setColor(Color.blue);
    g.drawRect(0,0,width-1,height-1);
    //写字母或数字
    g.setColor(Color.green);
    String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
    Random rd=new Random();
    StringBuilder sb=new StringBuilder();
    for(int i=1;i<=4;i++){
      int index = rd.nextInt(str.length());
      char c = str.charAt(index);
      sb.append(c);
      g.drawString(c+"",width/5*i,height/2);
    }
    String checkCode_session = sb.toString();
    //将验证码存入session
    req.getSession().setAttribute("checkCode_session",checkCode_session);
    //加干扰线
    g.setColor(Color.blue);
    for(int i=1;i<=10;i++){
      int x1 = rd.nextInt(width);
      int x2 = rd.nextInt(width);
      int y1 = rd.nextInt(height);
      int y2 = rd.nextInt(height);
      g.drawLine(x1,y1,x2,y2);
    }

    //输出展示
    ImageIO.write(image,"jpg",resp.getOutputStream());
  }

  @Override
  protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    this.doPost(req,resp);
  }
}

4.loginServlet类，用来判断验证码和用户名密码是否正确，注意先判断验证码；注意重定向和请求转发的不同，还有session的应用。

package Test;

import Test.dao.UserDao;
import Test.userclass.User;
import org.apache.commons.beanutils.BeanUtils;

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.IOException;
import java.lang.reflect.InvocationTargetException;
import java.util.Map;

@WebServlet("/loginServlet")
public class loginServlet extends HttpServlet {
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    //设置request编码
    request.setCharacterEncoding("utf-8");
    //获取参数
//    String username = request.getParameter("username");
//    String password = request.getParameter("password");
//    String checkCode = request.getParameter("checkCode");
//    User user=new User();
//    user.setUsername(username);
//    user.setPassword(password);
//    user.setCheckCode(checkCode);
    Map<String, String[]> parameterMap = request.getParameterMap();
    User user=new User();
    try {
      BeanUtils.populate(user,parameterMap);
    } catch (IllegalAccessException e) {
      e.printStackTrace();
    } catch (InvocationTargetException e) {
      e.printStackTrace();
    }
    UserDao userDao=new UserDao();
    //先判断验证码是否正确
    String checkCode_session = (String)request.getSession().getAttribute("checkCode_session");
    request.getSession().removeAttribute("checkCode_session");
    if(checkCode_session!=null && checkCode_session.equalsIgnoreCase(user.getCheckCode())){//忽略大小写
      //如果正确，判断用户名密码是否正确
      User login = userDao.login(user);
      if(login!=null){
        //登陆成功，存储用户信息
        request.getSession().setAttribute("username",login.getUsername());
        //重定向到success.jsp
        response.sendRedirect(request.getContextPath()+"/success.jsp");

      }else{//登陆失败，转发到登陆界面
        request.setAttribute("login_error","用户名或密码不正确");
        request.getRequestDispatcher("/login.jsp").forward(request,response);

      }
    }else{ //如果不正确，转发到登陆界面
      request.setAttribute("cc_error","验证码不正确");
      request.getRequestDispatcher("/login.jsp").forward(request,response);

    }
  }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    this.doPost(request, response);
  }
}

5.成功登陆界面

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
  <title>Title</title>
</head>
<body>

  <h1><%=request.getSession().getAttribute("username")%>,欢迎您</h1>

</body>
</html>

结果

登陆界面

验证码错误情况

用户名或密码不正确情况

成功登陆

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