前言

本文介绍的imagecode方法是一个生成图形验证码的请求，checkcode方法实现了对这个图形验证码的验证。从验证码的生成到验证的过程中，验证码是通过Session来保存的，并且设定一个验证码的最长有效时间为5分钟。验证码的生成规则是从0~9的数字中，随机产生一个4位数，并增加一些干扰元素，最终组合成为一个图形输出

1、验证码生成类

import java.awt.*;import java.awt.image.BufferedImage;import java.io.OutputStream;import java.util.HashMap;import java.util.Map;import java.util.Random;public class ImageCode { private static char mapTable[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9'}; public static Map<String, Object> getImageCode(int width, int height, OutputStream os) { Map<String,Object> returnMap = new HashMap<String, Object>(); if (width <= 0) width = 60; if (height <= 0) 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)); // 随机产生168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 < 168; 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); } //取随机产生的码 String strEnsure = ""; //4代表4位验证码,如果要生成更多位的认证码,则加大数值 for (int i = 0; i < 4; ++i) { strEnsure += mapTable[(int) (mapTable.length * Math.random())]; // 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))); //直接生成 String str = strEnsure.substring(i, i + 1); g.drawString(str, 13 * i + 6, 16); } // 释放图形上下文 g.dispose(); returnMap.put("image",image); returnMap.put("strEnsure",strEnsure); return returnMap; } //给定范围获得随机颜色 static Color getRandColor(int fc, int bc) { 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); }}

2、获取验证码API

@RequestMapping(value = "/images/imagecode")public String imagecode(HttpServletRequest request, HttpServletResponse response) throws Exception { OutputStream os = response.getOutputStream(); Map<String,Object> map = ImageCode.getImageCode(60, 20, os); String simpleCaptcha = "simpleCaptcha"; request.getSession().setAttribute(simpleCaptcha, map.get("strEnsure").toString().toLowerCase()); request.getSession().setAttribute("codeTime",new Date().getTime()); try { ImageIO.write((BufferedImage) map.get("image"), "JPEG", os); } catch (IOException e) { return ""; } return null;}

3、验证验证码API

@RequestMapping(value = "/checkcode")@ResponseBodypublic String checkcode(HttpServletRequest request, HttpSession session) throws Exception { String checkCode = request.getParameter("checkCode"); Object cko = session.getAttribute("simpleCaptcha") ; //验证码对象 if(cko == null){ request.setAttribute("errorMsg", "验证码已失效，请重新输入！"); return "验证码已失效，请重新输入！"; } String captcha = cko.toString(); Date now = new Date(); Long codeTime = Long.valueOf(session.getAttribute("codeTime")+""); if(StringUtils.isEmpty(checkCode) || captcha == null || !(checkCode.equalsIgnoreCase(captcha))) { request.setAttribute("errorMsg", "验证码错误！"); return "验证码错误！"; } else if ((now.getTime()-codeTime)/1000/60>5) { //验证码有效时长为5分钟 request.setAttribute("errorMsg", "验证码已失效，请重新输入！"); return "验证码已失效，请重新输入！"; }else { session.removeAttribute("simpleCaptcha"); return "1"; }}

总结

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