JSP彩色验证码
<%@ page contentType="image/jpeg" pageEncoding="gb2312"import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%><%!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);}%><%//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());//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 < 155; 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(10)); 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)));//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成 g.drawString(rand, 13 * i + 6, 16);}// 将认证码存入SESSIONsession.setAttribute("rand", sRand);// 图象生效g.dispose();// 输出图象到页面ImageIO.write(image, "JPEG", response.getOutputStream());//加上下面两条代码,运行时才不会出现java.lang.IllegalStateException: getOutputStream() has already been called ..........等异常out.clear();out = pageContext.pushBody();%>testimage.jsp<%@ page contentType="text/html;charset=gb2312"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head> <title>认证码输入页面</title> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <meta http-equiv="pragma" content="no-cache"> <meta http-equiv="cache-control" content="no-cache"> <meta http-equiv="expires" content="0"></head><body> <form method=post action="check.jsp"> <table> <tr> <td align=left> 系统产生的认证码： </td> <td> <img border=0 src="image.jsp"> </td> </tr> <tr> <td align=left> 输入上面的认证码： </td> <td> <input type=text name=rand maxlength=4 value=""> </td> </tr> <tr> <td colspan=2 align=center> <input type=submit value="提交检测"> </td> </tr> </table> </form></body></html>check.jsp<%@ page contentType="text/html; charset=gb2312" language="java"import="java.sql.*" errorPage=""%><html><head> <title>认证码验证页面</title> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <meta http-equiv="Pragma" content="no-cache"> <meta http-equiv="Cache-Control" content="no-cache"> <meta http-equiv="Expires" content="0"></head><body> <% String rand = (String) session.getAttribute("rand"); String input = request.getParameter("rand"); %> 系统产生的认证码为： <%=rand%> <br> 您输入的认证码为： <%=input%> <br> <br> <% if (rand.equals(input)) { %> <font color=green>输入相同，认证成功！</font> <% } else { %> <font color=red>输入不同，认证失败！</font> <% } %></body></html>
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