JSP/Servlet 实现简单的留言板

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package com.cnblogs.jbelial.Validation; import java.awt.*; import java.awt.image.BufferedImage; import java.io.* ; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; @SuppressWarnings("serial") public class ValidationCode extends HttpServlet { // 图形验证码的字符集合，系统通过随机从这些字符串中选择一些字符作为验证码 private static String codeChars = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTYVWXYZ" ; // 返回一个随机颜色 private static Color getRandomColor(int minColor , int maxColor) { Random random = new Random() ; if (minColor > 255) minColor = 255 ; if (maxColor > 255) maxColor = 255 ; // 获取颜色的随机值 int red = minColor + random.nextInt(maxColor - minColor) ; int green = minColor + random.nextInt(maxColor - minColor) ; int blue = minColor + random.nextInt(maxColor - minColor) ; return new Color(red,green,blue) ; } public void doGet (HttpServletRequest request , HttpServletResponse response) throws IOException { // 获取验证码集合的长度。 int charsLength = codeChars.length() ; // 关闭浏览器缓冲区 response.setHeader("ragma", "No-cache") ; response.setHeader("Cache-Control", "no-cache") ; response.setDateHeader("Expires", 0) ; // 设置图片传送的格式。 response.setContentType("image/jpeg"); // 设置图形验证码的长和宽度 int width = 90 ; int height = 20 ; // 建立图形缓冲区 BufferedImage image = new BufferedImage(width , height, BufferedImage.TYPE_INT_RGB) ; // 获取用于输出文字的Graphics对象 Graphics graphics = image.getGraphics() ; Random random = new Random() ; // 设置要填充的颜色 graphics.setColor(getRandomColor(180 , 250)) ; // 填充图形背景 graphics.fillRect(0, 0, width, height) ; // 设置初始字体和颜色 graphics.setFont(new Font("Time New Roman" , Font.ITALIC, height)) ; graphics.setColor(getRandomColor(120,180)) ; // 保存验证码 StringBuilder validationCode = new StringBuilder() ; // 验证码的随机字体 String[] fontNames = {"Times New Roman" , "Book antiqua" , "Arial" } ; // 随机生成验证码 for (int i = 0 ; i < 4 ; ++ i) { // 设置当前验证码字符的字体 graphics.setFont(new Font(fontNames[random.nextInt(3)] , Font.ITALIC , height)) ; // 随机获得验证码的字符 char codeChar = codeChars.charAt(random.nextInt(charsLength)) ; validationCode.append(codeChar) ; graphics.setColor(getRandomColor(20,120)) ; // 在图形上输出验证码字符 graphics.drawString(String.valueOf(codeChar), 16*i+random.nextInt(7), height - random.nextInt(6) ) ; } // 获得Session对象，并设置Session对象为3分钟 HttpSession session = request.getSession(); session.setMaxInactiveInterval(5*60) ; // 将验证码放入session对象中. session.setAttribute("validationCode",validationCode.toString() ) ; // 关闭graphics对象。 graphics.dispose() ; // 向客户端发送图形验证码 ImageIO.write(image,"JPEG" ,response.getOutputStream()) ; } public void doPost (HttpServletRequest request , HttpServletResponse response) throws IOException { doGet(request , response) ; } }