session_login

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<title>Insert title here</title><script type="text/javascript">    function changeImage(){        document.getElementById("myimage").src = "/d_session/checkimage?"+new Date().getTime();    }</script></head><body>    <h3>XX网站的登录页面</h3>    <font color="red" size="5">${message }</font>    <form action="/d_session/login" method="post">        用户名:<input type="text" name="username"><br/>        密码:<input type="password" name="password"><br/>        验证码:<input type="text" name="checkcode">        <img src="/d_session/checkimage" style="cursor: pointer" onclick="changeImage();" id="myimage"><br/>        <input type="submit" value="登录">    </form></body>

CheckImageServlet doGet

public class CheckImageServlet extends HttpServlet {    private final int WIDTH = 120;      private final int HEIGHT = 30;    public void doGet(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        BufferedImage bf = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);        Graphics2D graphics = (Graphics2D) bf.getGraphics();//--Graphics2D is Graphics's child        Color color = new Color(203, 222, 225);        graphics.setColor(color);        graphics.fillRect(0, 0, WIDTH, HEIGHT);        String base ="ABCDEFGHIJKLMN";        Random random = new Random();        graphics.setColor(Color.RED);        graphics.setFont(new Font("楷体",Font.BOLD,18));        int m = 13;        StringBuilder sb = new StringBuilder();        for (int i = 0; i < 4; i++) {            int index = random.nextInt(base.length());            char charAt = base.charAt(index);            int jiaodu = random.nextInt(60)-30;            double theta = jiaodu*Math.PI/180;            graphics.rotate(theta,  m, 15);            graphics.drawString(charAt+"", m, 19);            sb.append(charAt);            graphics.rotate(-theta,  m, 15);            m+=20;        }    request.getSession().setAttribute("checkcode_session", sb.toString());        graphics.setColor(Color.BLUE);        for (int i = 0; i < 4; i++) {            int x1 = random.nextInt(WIDTH);            int x2 = random.nextInt(WIDTH);            int y1 = random.nextInt(HEIGHT);            int y2 = random.nextInt(HEIGHT);            graphics.drawLine(x1, y1, x2, y2);        }        graphics.dispose();        ImageIO.write(bf, "png", response.getOutputStream());    }    public void doPost(HttpServletRequest request, HttpServletResponse response)            throws ServletException, IOException {        doGet(request, response);    }}

LoginServlet doGet

        request.setCharacterEncoding("UTF-8");        String username = request.getParameter("username");        String password = request.getParameter("password");        String checkcode = request.getParameter("checkcode");        String checkcode_session = (String) request.getSession().getAttribute("checkcode_session");    if(checkcode==null||!checkcode.equalsIgnoreCase(checkcode_session)){            request.setAttribute("message", "对不起, 您输入验证码信息不正确...");     request.getRequestDispatcher("/login.jsp").forward(request, response);            return ;        }        // 做用户名和密码的校验        // admin         if("admin".equals(username)&&"admin".equals(password)){            request.getSession().setAttribute("loginUser", "admin");            response.sendRedirect(request.getContextPath()+"/index.jsp");   }else{            request.setAttribute("message", "对不起, 您 是用户名或密码不正确...");request.getRequestDispatcher("/login.jsp").forward(request, response);          }

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