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实现带有验证码的简易登录页面

作者:互联网

需求:
  1. 访问带有验证码的登录页面login.jsp
  2. 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

login.jsp页面代码:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>login</title>
    <script>
       /*
            分析:
                点击图片,需要换一张
                1.给图片绑定单击事件
                2.重新设置图片的src属性值
           */
       window.onload = function(){
         document.getElementById("img").onclick = function(){
          this.src="/yanzhengma_war_exploded/checkCodeServlet?time="+new Date().getTime();
         }
       }
</script>

  <style> div{ color: red; } </style> </head> <body> <form action="/yanzhengma_war_exploded/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="/yanzhengma_war_exploded/checkCodeServlet"></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>

 

 

 

生成验证码的代码:

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {



        //设置验证码框的宽、高
        int width = 100;
        int height = 50;

        //1.创建一对象,在内存中图片(验证码图片对象)
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);


        //2.美化图片
        //2.1 填充背景色
        Graphics g = image.getGraphics();//画笔对象
        g.setColor(Color.PINK);//设置画笔颜色
        g.fillRect(0,0,width,height);

        //2.2画边框
        g.setColor(Color.BLUE);
        //宽高不减一,会有一半的边框样式体现不出来
        g.drawRect(0,0,width - 1,height - 1);

        String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz0123456789";
        //生成随机角标
        Random ran = new Random();
        StringBuilder sb = new StringBuilder();
        //验证码有4个数,故循环四次
        for (int i = 1; i <= 4; i++) {
            int index = ran.nextInt(str.length());
            //获取字符
            char ch = str.charAt(index);//随机字符
            sb.append(ch);

            //2.3写验证码
            g.drawString(ch+"",width/5*i,height/2);
        }
        String checkCode_session = sb.toString();
        //将验证码存入session
        request.getSession().setAttribute("checkCode_session",checkCode_session);

        //2.4画干扰线
        g.setColor(Color.GREEN);

        //随机生成坐标点
        for (int i = 0; i < 10; i++) {
            int x1 = ran.nextInt(width);
            int x2 = ran.nextInt(width);

            int y1 = ran.nextInt(height);
            int y2 = ran.nextInt(height);
            //两点确定一线,点(x1,y1)到点(x2,y2)形成一条线
            g.drawLine(x1,y1,x2,y2);
        }


        //3.将图片输出到页面展示
        ImageIO.write(image,"jpg",response.getOutputStream());            

 

loginServlet代码:(用户的登录涉及到数据库的操作,此处将DAO省去,简化编写 )

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.设置request编码
        request.setCharacterEncoding("utf-8");
        //2.获取参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        String checkCode = request.getParameter("checkCode");
        //3.先获取生成的验证码
        HttpSession session = request.getSession();
        String checkCode_session = (String) session.getAttribute("checkCode_session");
        //删除session中存储的验证码,为了防止返回登陆页面后原验证码依旧可用
        session.removeAttribute("checkCode_session");
        //3.先判断验证码是否正确
        if(checkCode_session!= null && checkCode_session.equalsIgnoreCase(checkCode)){
            //忽略大小写比较
            //验证码正确
            //判断用户名和密码是否一致
            if("zhangsan".equals(username) && "123".equals(password)){//需要调用UserDao查询数据库
                //登录成功
                //存储信息,用户信息
                session.setAttribute("user",username);
                //重定向到success.jsp
                response.sendRedirect(request.getContextPath()+"/success.jsp");
            }else{
                //登录失败
                //存储提示信息到request
                request.setAttribute("login_error","用户名或密码错误");
                //转发到登录页面
                request.getRequestDispatcher("/login.jsp").forward(request,response);
            }


        }else{
            //验证码不一致
            //存储提示信息到request
            request.setAttribute("cc_error","验证码错误");
            //转发到登录页面
            request.getRequestDispatcher("/login.jsp").forward(request,response);

        }

    }

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

 

success.jsp页面代码:

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

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

</body>
</html>

 

标签:登录,checkCode,request,验证码,session,jsp,页面
来源: https://www.cnblogs.com/churujianghudezai/p/11795680.html