JAVA驗證碼生成包括（包括算數計算值和純char驗證）

package com.jiliang;

import com.google.code.kaptcha.Constants;
import com.google.code.kaptcha.Producer;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;

import javax.annotation.Resource;
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;

/**
 * 圖片驗證碼（支持算術形式）
 *
 * @author admin
 */
@Controller
@RequestMapping("/validate")
public class SysCaptchaController{
    @Resource(name = "captchaProducer")
    private Producer captchaProducer;

    @Resource(name = "captchaProducerMath")
    private Producer captchaProducerMath;

    /**
     * 驗證碼生成
     */
    @GetMapping(value = "/image")
    public void getKaptchaImage(HttpServletRequest request, HttpServletResponse response) {
        ServletOutputStream out = null;
        try {
            HttpSession session = request.getSession();
            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");

            String type = request.getParameter("type");
            String capStr = null;
            String code = null;
            BufferedImage bi = null;
            if ("math".equals(type)) {
                String capText = captchaProducerMath.createText();
                capStr = capText.substring(0, capText.lastIndexOf("@"));
                code = capText.substring(capText.lastIndexOf("@") + 1);
                bi = captchaProducerMath.createImage(capStr);
            } else if ("char".equals(type)) {
                capStr = code = captchaProducer.createText();
                bi = captchaProducer.createImage(capStr);
            }
            //將生成的code存放到session中，待登陸後從session獲取比較
            //鍵值爲：KAPTCHA_SESSION_KEY
            session.setAttribute(Constants.KAPTCHA_SESSION_KEY, code);
            out = response.getOutputStream();
            ImageIO.write(bi, "jpg" , out);
            out.flush();

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (out != null) {
                    out.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

注：需要到一個jar包

<!-- https://mvnrepository.com/artifact/com.github.penggle/kaptcha -->
<dependency>
    <groupId>com.github.penggle</groupId>
    <artifactId>kaptcha</artifactId>
    <version>2.3.2</version>
</dependency>