Java图片验证码的生成与验证

前言：这篇文章里面的代码是基于spring boot的，直接拷贝可用，可以先用了再去理解里面原理
1.请求获取验证码图片的API：CaptchaController.java

**
 * Author: SamGroves
 *
 * Description: 该Api能够直接获取到验证码图片
 *
 * Date: 2017/8/29
 */
@Controller
@RequestMapping("/api")
public class CaptchaController {
    /**
     * 用于生成带四位数字验证码的图片
     */
    @RequestMapping(value = "/captcha")
    @ResponseBody
    public String imagecode(HttpServletRequest request, HttpServletResponse response) throws Exception {
        response.setDateHeader("Expires", 0);
        response.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");
        response.addHeader("Cache-Control", "post-check=0, pre-check=0");
        response.setHeader("Pragma", "no-cache");
        response.setContentType("image/jpeg");
        
        OutputStream os = response.getOutputStream();
        //返回验证码和图片的map
        Map<String,Object> map = Captcha.getImageCode(86, 37, 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"), "jpg", os);
        } catch (IOException e) {
            return "";
        }   finally {
            if (os != null) {
                os.flush();
                os.close();
            }
        }
        return null;
    }
}

2.验证前端输入的验证码API：

/**
 * Author: SamGroves
 *
 * Description: 获得前端输入验证码的验证
 *
 * Date: 2017/8/26
 */

@Controller
@RequestMapping("/api")
public class VerifyController extends BaseController{
    /**
     * @param checkCode 前端用户输入返回的验证码
     * 参数若需要，自行添加
     */
    @RequestMapping(value = "/verify")
    @ResponseBody
    public String checkcode(HttpServletRequest request,
                            HttpSession session,
                            String checkCode) throws Exception {
      
        // 获得验证码对象
        Object cko = session.getAttribute("simpleCaptcha"); 
        if (cko == null) {
            request.setAttribute("errorMsg", "请输入验证码！");
            return "请输入验证码！";
        }
        String captcha = cko.toString();
        // 判断验证码输入是否正确
        if (StringUtils.isEmpty(checkCode) || captcha == null || !(checkCode.equalsIgnoreCase(captcha))) {
            request.setAttribute("errorMsg", "验证码错误！");
            return "验证码错误，请重新输入！";

          // 验证码有效时长为1分钟
        Date now = new Date();
        Long codeTime = Long.valueOf(session.getAttribute("codeTime") + "");
        } else if ((now.getTime() - codeTime) / 1000 / 60 > 1) {
            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 {

           // 在这里可以处理自己需要的事务，比如验证登陆等

            return "验证通过！";
        }
    }
}

3.前两个接口类中所包含的方法的工具类：Captcha.java

/**
 * Author: SamGroves
 *
 * Description: 验证码生成器
 *
 * Date: 2017/8/29
 */
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 Captcha {
    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);
            // 设置随便码在背景图图片上的位置
            g.drawString(str, 13 * i + 20, 25);
        }
        // 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);
    }
}

结语：前端显示图片验证码并能点击图片重新请求方法：http://127.0.0.1:8080/api//captcha + new date();

原文作者：@疯狂的米老鼠(已授权)    
文章地址：http://www.jianshu.com/p/29f005992527

Java图片验证码的生成与验证

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