导入以下依赖

<!--图片验证码-->
        <dependency>
            <groupId>com.github.whvcse</groupId>
            <artifactId>easy-captcha</artifactId>
            <version>1.6.2</version>
        </dependency>

 编写controller

package com.anXin.user.controller;


import com.wf.captcha.*;
import com.wf.captcha.base.Captcha;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

@Controller
public class KaptchaController {

    private static final Logger logger = LoggerFactory.getLogger(KaptchaController.class);
    public static HttpSession session;

    @RequestMapping(path = "/kaptcha",method = RequestMethod.GET)
    public void getKaptcha(HttpServletResponse response, HttpSession session) throws Exception {
        Random r=new Random();
        int a = r.nextInt(5) + 1;
        switch (a){
            case 1:get1(response, session);break;
            case 2:get2(response, session);break;
            case 3:get3(response, session);break;
            case 4:get4(response, session);break;
            case 5:get5(response, session);break;
        }
    }

    private void get1(HttpServletResponse response, HttpSession session){
        SpecCaptcha captcha = new SpecCaptcha(130, 40);
        System.out.println("验证码为："+captcha.text());
        session.setAttribute("captcha",captcha.text());
        response.setContentType("image/png");
        try {
            OutputStream os = response.getOutputStream();
            captcha.out(os);
        } catch (IOException e) {
            logger.error("响应验证码失败" + e.getMessage());
        }
    }
    private void get2(HttpServletResponse response, HttpSession session) throws Exception {
        GifCaptcha gifCaptcha = new GifCaptcha(130, 40);
        gifCaptcha.setCharType(Captcha.TYPE_ONLY_UPPER);
        //设置字体
        gifCaptcha.setFont(Captcha.FONT_5);
        System.out.println("验证码为："+gifCaptcha.text());
        session.setAttribute("captcha",gifCaptcha.text());
        response.setContentType("image/gif");
        OutputStream os = response.getOutputStream();
        gifCaptcha.out(os);
    }
    private void get3(HttpServletResponse response, HttpSession session){
        ChineseCaptcha chineseCaptcha = new ChineseCaptcha(130, 40);
        System.out.println("验证码为："+chineseCaptcha.text());
        session.setAttribute("captcha",chineseCaptcha.text());
        response.setContentType("image/png");
        try {
            OutputStream os = response.getOutputStream();
            chineseCaptcha.out(os);
        } catch (IOException e) {
            logger.error("响应验证码失败" + e.getMessage());
        }
    }
    private void get4(HttpServletResponse response, HttpSession session){
        ChineseGifCaptcha chineseGifCaptcha = new ChineseGifCaptcha(130, 40);
        System.out.println("验证码为："+chineseGifCaptcha.text());
        session.setAttribute("captcha",chineseGifCaptcha.text());
        response.setContentType("image/gif");
        try {
            OutputStream os = response.getOutputStream();
            chineseGifCaptcha.out(os);
        } catch (IOException e) {
            logger.error("响应验证码失败" + e.getMessage());
        }
    }
    private void get5(HttpServletResponse response, HttpSession session){
        ArithmeticCaptcha arithmeticCaptcha = new ArithmeticCaptcha(180, 40);
        //设置几位数的运算，几个数计算
        arithmeticCaptcha.setLen(3);
        //打印算式
        System.out.println("算式为："+arithmeticCaptcha.getArithmeticString());
        System.out.println("验证码为："+arithmeticCaptcha.text());
        session.setAttribute("captcha",arithmeticCaptcha.text());
        response.setContentType("image/png");
        try {
            OutputStream os = response.getOutputStream();
            arithmeticCaptcha.out(os);
        } catch (IOException e) {
            logger.error("响应验证码失败" + e.getMessage());
        }
    }
}

以上为随机生成五种不同效果的验证码图片，可以根据自己的需求灵活改写

测试结果