JSP验证码页面-Serverlet

浏览数：23 / 时间：2015年06月09日

使用 Get方法，通过设置session和request设置页面状态

 <body>
        <div>
        <form method=get>
            <tr>
                <td align=left>请输入认证码：<input type=text name=rand maxlength=4 value=""></td>
                <td><img border=0 src="checkcode" onclick="this.src = ‘checkcode?a=‘ + Math.random() + 100"></td>
                <td colspan=2 align=center><input type=submit value="check"></td>
            </tr>
        </form>
            
        <%
            String rand = (String) session.getAttribute("rand");
            String input = request.getParameter("rand");
            if (input != null) {
                if (rand.equals(input)) {
        %>
        <font color=green>验证码正确！</font>
        <%
        } else {
        %>
        <font color=red>验证码错误！</font>
        <%
                }
            }
        %>
        </div>
    </body>

上面是login.jsp下面是serverlet的

protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //设置页面不缓存
        response.setHeader("Pragma","No-cache");
        response.setHeader("Cache-Control","no-cache");
        response.setDateHeader("Expires", 0);

        // 在内存中创建图象
        int width=60, height=20;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

        // 获取图形上下文
        Graphics g = image.getGraphics();

        //生成随机类
        Random random = new Random();

        // 设定背景色
        g.setColor(getRandColor(200,250));
        g.fillRect(0, 0, width, height);

        //设定字体
        g.setFont(new Font("Times New Roman",Font.PLAIN,18));

        //画边框
        g.setColor(new Color(height));
        g.drawRect(0,0,width-1,height-1);


        // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
        g.setColor(getRandColor(160,200));
        for (int i=0;i<150;i++)
        {
                int x = random.nextInt(width);
                int y = random.nextInt(height);
                int xl = random.nextInt(12);
                int yl = random.nextInt(12);
                g.drawLine(x,y,x+xl,y+yl);
        }

        // 取随机产生的认证码(4位数字)
        String sRand="";
        for (int i=0;i<4;i++){
            String rand=String.valueOf(random.nextInt(36));
                    if(Integer.parseInt(rand)>9){            
                        int a = Integer.parseInt(rand)-9+64;
                        rand = String.valueOf((char)a);
                        //生成随机大写字母
                    }
                    sRand+=rand;
            // 将认证码显示到图象中
            g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
            g.drawString(rand,13*i+6,16);
        }

        // 将认证码存入SESSION
        HttpSession session = request.getSession(); 
        session.setAttribute("rand",sRand);


        // 图象生效
        g.dispose();

        // 输出图象到页面
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }

   
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

     Color getRandColor(int fc,int bc){//给定范围获得随机颜色
        Random random = new Random();
        if(fc>255) fc=255;
        if(bc>255) bc=255;
        int r=fc+random.nextInt(bc-fc);
        int g=fc+random.nextInt(bc-fc);
        int b=fc+random.nextInt(bc-fc);
        return new Color(r,g,b);
        }