Code learning session +

 

 analysis

 

 

LoginServlet class

@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");

        determine whether the correct verification code//
        The session = the HttpSession request.getSession ();
         // get a code value 
        String checkCode_session = (String) session.getAttribute ( "checkCode" );
         // a complete acquisition, delete it immediately, in order to ensure a one-time authentication code 
        session. removeAttribute ( "checkCode" );
         iF (! checkCode_session = null && checkCode_session.equalsIgnoreCase (checkcode)) { // case-insensitive comparison
             // code is correct
             // 1. Analyzing codes and passwords are consistent 
            iF ( "zhangsan" .equals (username) && "123".the equals (password)) { // perfect userDao need to call to query the database
                 // landing successfully
                 //1. The user information stored 
                session.setAttribute ( "User" , username);
                 // 2. redirection success.jsp 
                Response.sendRedirect (request.getContextPath () + "/ success.jsp" ); 


            } the else {
                 // login failed
                 // 1. storage information to request domain 
                request.setAttribute ( "login_error", "user name or password is incorrect" );
                 // 2. forwarding 
                request.getRequestDispatcher ( "/ the login.jsp" ) .forward (request, the Response );
            } 

        } The else {
             // this code is not correct
             @1.存储信息到request域中
            request.setAttribute("cc_error","验证码不正确");
            //2.转发
            request.getRequestDispatcher("/login.jsp").forward(request,response);
        }
    }

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

Servlet class codes

@WebServlet("/checkCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        int width=100;
        int height=50;
        BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        g.setColor(Color.green);
        g.drawRect(0,0,width,height);
        g.setColor(Color.yellow);
        g.fillRect(0,0,width-1,height-1);

        String str="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        Random random=new Random();
        g.setColor(Color.magenta);

        StringBuilder sb = new StringBuilder();
        for (int i=1;i<=4;i++){
            int index = random.nextInt(str.length());
            char ch=str.charAt(index);
            g.drawString(ch+"",i*width/5,height/2);
            sb.append(ch);
        }
        String checkCode_session = sb.toString();
        HttpSession session=request.getSession();
        session.setAttribute("checkCode",checkCode_session);

        System.out.println("验证码是   :  " + checkCode_session);

        //画干扰线
        g.setColor(Color.green);
        for (int i = 0; i < 16; i++) {
            int x1=random.nextInt(width);
            int x2=random.nextInt(width);
            int y1=random.nextInt(height);
            int y2=random.nextInt(height);
            g.drawLine(x1,y1,x2,y2);
        }
        ImageIO.write(image,"jpg",response.getOutputStream());
    }

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

login.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>login</title>
    <script>
        window.onload=function () {
            var img = document.getElementById('img');
            img.onclick=function () {
                var date=new Date().getTime();
                // img.src="/session/checkCodeServlet?"+date
                this.src="/session/checkCodeServlet?time="+date
            }
        }
    </script>
    <style>
        div{
            color: red;
        }
    </style>
</head>
<body>
    <form action="/session/loginServlet">
        <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>
            <codes>TD<>TR
                </td>
                <td><input type="text" name="checkcode"></td>
            </tr>
            <tr>
                <td colspan="2"><img id="img" src="/session/checkCodeServlet"></td>
            </tr>
            <tr>
                <td colspan="2"><input type="submit" value="登录"></td>
            </tr>
        </table>
    </form>

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

</body>
</html>

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 success.jsp

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

欢迎登录，<h1><%=request.getSession().getAttribute("user") %></h1>
</body>
</html>

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