JSP验证码页面-Servlet
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Servlet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); }
