SpringMVC下获取验证码实例详解

前言：

1.用户一开始登录的时候, 不建议出现验证码, 这一点在很多网站上已经体现的很好了, 只有当用户连续输错三次或者以上才会要求用户输入验证码.

2.记录用户输错次数最好不要使用 session 来记录, 因为 session 是跟客户端浏览器会话有关的, 如果用重启浏览器或者换新的浏览器再来登录或者试错, 就是新的回话了, 原来记录的错误次数就失效了. 建议此处采用缓存机制来实现, 简单处理就是采用 Map<用户登录id, 错误次数> 来实现, 如果有多台服务器负载的话, 就需要采用另外的缓存机制, 比如采用 Redis.

3.当用户输入完用户名以后, 就需要用登录名进行判断, 是否需要进行验证码校验.

4.生成的验证码与 session 绑定, 是否需要校验验证码, 要根据用户规定时间内失败的次数来判断.

原生的 servlet 可以直接 write 图片到客户端. 但是刚用 springMVC 的童鞋可能不知道怎么在此框架下返回图片. 其实在本质上用 spring 返回图片跟用 servlet 是一样的。都是使用的 HttpServletResponse 来返回图片.

springMVC 的 controller 里获取验证码的方法

/** * 生成验证码 * @param request * @param response */ @RequestMapping(value = "login/getVerifyCode") public void getVerifyCode(HttpServletRequest request,HttpServletResponse response){ response.setHeader("Pragma","No-cache"); response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expires", 0); response.setContentType("image/jpeg"); //生成随机字符串 String verifyCode = VerifyCodeUtils.generateVerifyCode(4); //存入Session, 此处可以根据自己的需求 HttpSession session = request.getSession(); session.setAttribute("verifyCode",verifyCode); //生成图片 int w = 100, h = 35; try { //将图片写入到 response 的输出流即可将图片返回到客户端了 VerifyCodeUtils.outputImage(w, h , response.getOutputStream(), verifyCode); } catch (IOException e) { logger.error("生成验证码失败, Cause by: {}", e.getMessage(), e); } }

生成验证码图片的类

网上找到的一个, 还不错.

import javax.imageio.ImageIO;import java.awt.*;import java.awt.geom.AffineTransform;import java.awt.image.BufferedImage;import java.io.File;import java.io.FileOutputStream;import java.io.IOException;import java.io.OutputStream;import java.util.Arrays;import java.util.Random;/** * 生成图片流 * @Description: Created by zcqshine on 2017/5/18. */public class VerifyCodeUtils { private static final String VERIFY_CODES = "23456789ABCDEFGHJKLMNPQRSTUVWXYZ"; private static Random random = new Random(); /** * 使用系统默认字符源生成验证码 * @param verifySize 验证码长度 * @return */ public static String generateVerifyCode(int verifySize){ return generateVerifyCode(verifySize, VERIFY_CODES); } /** * 使用指定源生成验证码 * @param verifySize 验证码长度 * @param sources 验证码字符源 * @return */ public static String generateVerifyCode(int verifySize, String sources){ if (sources == null || sources.trim().length() == 0){ sources = VERIFY_CODES; } int codesLen = sources.length(); Random rand = new Random(System.currentTimeMillis()); StringBuilder verifyCode = new StringBuilder(verifySize); for (int i = 0; i < verifySize; i++){ verifyCode.append(sources.charAt(rand.nextInt(codesLen -1 ))); } return verifyCode.toString(); } /** * 输出随机验证码图片流, 并返回验证码值 * @param w * @param h * @param outputFile * @param verifySize * @return */ public static String outputVerifyImage(int w, int h, File outputFile, int verifySize) throws IOException{ String verifyCode = generateVerifyCode(verifySize); outputImage(w,h,outputFile,verifyCode); return verifyCode; } /** * 生成指定验证码图像文件 * @param w * @param h * @param outputFile * @param verifyCode * @throws IOException */ public static void outputImage(int w, int h, File outputFile, String verifyCode) throws IOException{ if (outputFile == null){ return; } File dir = outputFile.getParentFile(); if(!dir.exists()){ dir.mkdirs(); } try { outputFile.createNewFile(); FileOutputStream fos = new FileOutputStream(outputFile); outputImage(w, h, fos, verifyCode); fos.close(); } catch (IOException e) { throw e; } } public static void outputImage(int w, int h, OutputStream os, String code) throws IOException{ int verifySize = code.length(); BufferedImage image = new BufferedImage(w,h, BufferedImage.TYPE_INT_RGB); Random rand = new Random(); Graphics2D g2 = image.createGraphics(); g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON); Color[] colors = new Color[5]; Color[] colorSpaces = new Color[]{Color.WHITE, Color.CYAN, Color.GRAY, Color.LIGHT_GRAY, Color.MAGENTA, Color.ORANGE, Color.PINK, Color.YELLOW}; float[] fractions = new float[colors.length]; for (int i = 0; i < colors.length; i++){ colors[i] = colorSpaces[rand.nextInt(colorSpaces.length)]; fractions[i] = rand.nextFloat(); } Arrays.sort(fractions); g2.setColor(Color.GRAY); //设置边框色 g2.fillRect(0,0, w, h); Color c = getRandColor(200, 250); g2.setColor(c); //设置背景色 g2.fillRect(0, 2, w, h-4); //绘制干扰线 Random random = new Random(); g2.setColor(getRandColor(160, 200));// 设置线条的颜色 for (int i = 0; i < 20; i++) { int x = random.nextInt(w - 1); int y = random.nextInt(h - 1); int xl = random.nextInt(6) + 1; int yl = random.nextInt(12) + 1; g2.drawLine(x, y, x + xl + 40, y + yl + 20); } // 添加噪点 float yawpRate = 0.05f;// 噪声率 int area = (int) (yawpRate * w * h); for (int i = 0; i < area; i++) { int x = random.nextInt(w); int y = random.nextInt(h); int rgb = getRandomIntColor(); image.setRGB(x, y, rgb); } shear(g2, w, h, c);// 使图片扭曲 g2.setColor(getRandColor(100, 160)); int fontSize = h-4; Font font = new Font("Algerian", Font.ITALIC, fontSize); g2.setFont(font); char[] chars = code.toCharArray(); for(int i = 0; i < verifySize; i++){ AffineTransform affine = new AffineTransform(); affine.setToRotation(Math.PI / 4 * rand.nextDouble() * (rand.nextBoolean() ? 1 : -1), (w / verifySize) * i + fontSize/2, h/2); g2.setTransform(affine); g2.drawChars(chars, i, 1, ((w-10) / verifySize) * i + 5, h/2 + fontSize/2 - 10); } g2.dispose(); ImageIO.write(image, "jpg", os); } private static Color getRandColor(int fc, int bc) { 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); } private static int getRandomIntColor() { int[] rgb = getRandomRgb(); int color = 0; for (int c : rgb) { color = color << 8; color = color | c; } return color; } private static int[] getRandomRgb() { int[] rgb = new int[3]; for (int i = 0; i < 3; i++) { rgb[i] = random.nextInt(255); } return rgb; } private static void shear(Graphics g, int w1, int h1, Color color) { shearX(g, w1, h1, color); shearY(g, w1, h1, color); } private static void shearX(Graphics g, int w1, int h1, Color color) { int period = random.nextInt(2); boolean borderGap = true; int frames = 1; int phase = random.nextInt(2); for (int i = 0; i < h1; i++) { double d = (double) (period >> 1) * Math.sin((double) i / (double) period + (6.2831853071795862D * (double) phase) / (double) frames); g.copyArea(0, i, w1, 1, (int) d, 0); if (borderGap) { g.setColor(color); g.drawLine((int) d, i, 0, i); g.drawLine((int) d + w1, i, w1, i); } } } private static void shearY(Graphics g, int w1, int h1, Color color) { int period = random.nextInt(40) + 10; // 50; boolean borderGap = true; int frames = 20; int phase = 7; for (int i = 0; i < w1; i++) { double d = (double) (period >> 1) * Math.sin((double) i / (double) period + (6.2831853071795862D * (double) phase) / (double) frames); g.copyArea(i, 0, 1, h1, 0, (int) d); if (borderGap) { g.setColor(color); g.drawLine(i, (int) d, i, 0); g.drawLine(i, (int) d + h1, i, h1); } } }public static void main(String[] args) { File dir = new File("/Users/zcqshine/Downloads/test"); int w = 200, h= 80; for (int i = 0; i< 50; i++){ String verifyCode = generateVerifyCode(4); File file = new File(dir, verifyCode + ".jpg"); try { outputImage(w, h, file, verifyCode); } catch (IOException e) { e.printStackTrace(); } } }}

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