Spring Boot 验证码的生成和验证详解

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);
 }
}

@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;
}

@RequestMapping(value = "/checkcode")
@ResponseBody
public 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";
 }
}