后台生成4位图像验证码

主要依赖：

   com.github.penggle
   kaptcha
   2.3.2

spring相关依赖参照用到的另行添加。

package com.math.controller;

import com.google.code.kaptcha.Producer;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.util.StringUtils;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.imageio.ImageIO;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.image.BufferedImage;
import java.io.IOException;

/**
 * @ClassName: VerifyCodeController
 * @Description: 图像验证码
 * @author: math
 * @date: 2023/1/16 16:33
 * @version: 1.0
 */
@Controller
@RequestMapping("/verifyCode")
public class VerifyCodeController {
    public static final String KAPTCHA_SESSION_KEY = "kaptcha_key";

    @Autowired
    private Producer producer = null;

    /**
     * @Author Math
     * @Description 生成验证码
     * @Date  2023/1/16
     * @Version 1.0
     * @Param
     * @return
     **/
    @RequestMapping("/getImg")
    public void getImg(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ServletOutputStream out = null;
        try {
            // 设置页面不缓存
            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");
            // 生成验证码编码
            String capText = producer.createText();
            // 将验证码编码生成图片
            BufferedImage kaptchaImage = producer.createImage(capText);
            // 输出验证码PNG格式图片
            response.setHeader("content-type", "image/png");
            out = response.getOutputStream();
            ImageIO.write(kaptchaImage, "png", out);
            out.flush();
            // 获取session，并将验证码编码存放到session中
            HttpSession session = request.getSession();
            session.setAttribute(KAPTCHA_SESSION_KEY, capText);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * @Author Math
     * @Description 检验验证码
     * @Date  2023/1/16
     * @Version 1.0
     * @Param
     * @return
     **/
    public boolean captchaVerify(HttpServletRequest request, String kaptchaCode) throws Exception {
        HttpSession session = request.getSession();
        String code = (String) session.getAttribute(KAPTCHA_SESSION_KEY);
        System.out.println("kaptchaCode:" + kaptchaCode + "  ;code:" + code);
        if (!StringUtils.isEmpty(kaptchaCode) && kaptchaCode.equalsIgnoreCase(code)) {
            // 检验通过
            return true;
        }
        return false;
    }
}

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