java实现随机验证码图片生成

 /**
     * 获取随机数验证码图片
     *
     * @param request  HttpServletRequest
     * @param response HttpServletResponse
     */
    @GetMapping(value = "/getRandomCode" ,produces = MediaType.APPLICATION_OCTET_STREAM_VALUE)
    public void getRandomCode(HttpServletRequest request, HttpServletResponse response) {
        baseService.getRandomCode(request, response);
}

void getRandomCode(HttpServletRequest request, HttpServletResponse response);

@Autowired
 private RedisTemplate redisTemplate;
    @Autowired
    private CodeImageUtils codeImageUtils;
    /**
     *  获取随机数验证码图片
     */
    @Override
    public void getRandomCode(HttpServletRequest request, HttpServletResponse response) {
        try {
            // 设置输出类型为图片
            response.setContentType("image/jpeg");
            // 生成随机码
            String verificationCode = codeImageUtils.getRandomCode();
            // 背景颜色与字符颜色
            Color color = codeImageUtils.getRandomColor();
            Color reverseColor = codeImageUtils.getReverseColor(color);
            //创建一张彩色的图片
            BufferedImage bi = new BufferedImage(100, 30, BufferedImage.TYPE_INT_RGB);
            Graphics2D graphics = bi.createGraphics();
            //设置字体
            graphics.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 16));
            graphics.setColor(color);
            //绘制背景
            graphics.fillRect(0, 0, 100, 30);
            graphics.setColor(reverseColor);
            //绘制字符
            graphics.drawString(verificationCode, 18, 20);
            //绘制最多50个随机噪点//绘制最多50个随机噪点
            Random random = new Random();
            int n = random.nextInt(50);
            for (int i = 0; i < n; i++) {
                graphics.drawRect(100, 30, 1, 1);
            }
            // 放到redis中 sessionId:code,过期时间60s
            redisTemplate.opsForValue().set(request.getSession().getId(),verificationCode,60, TimeUnit.SECONDS);
            //输出到客户端
            ServletOutputStream sos = response.getOutputStream();
            JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(sos);
            encoder.encode(bi);
            sos.flush();
        }catch (Exception ex){
            log.error("生成验证码失败！",ex);
        }
    }

@Component
public class CodeImageUtils {
    @Autowired
    RedisTemplate redisTemplate;
    /**
     * 生成4位随机的验证码字符串
     *
     * @return
     */
    public  String getRandomCode() {
        // 通过random生成4位随机数字码
        Random random = new Random();
        StringBuilder rs = new StringBuilder();
        for (int i = 0; i < 4; i++) {
            rs.append(random.nextInt(10));
        }
        return rs.toString();
    }
    /**
     * 生成随机的颜色
     *
     * @return
     */
    public  Color getRandomColor() {
        Random random = new Random();
        return new Color(random.nextInt(255), random.nextInt(255), random.nextInt(255));
    }
    /**
     * 获取某颜色的反色
     * @param color
     * @return
     */
    public  Color getReverseColor(Color color) {
        return new Color(255 - color.getRed(), 255 - color.getGreen(), 255 - color.getBlue());
    }
    /**
     * 校验
     * @param code
     * @return
     */
    public boolean valid(HttpServletRequest request,String code){
        // 获取缓存的code
       Object cacheCode =  redisTemplate.opsForValue().get(request.getSession().getId());
       if(cacheCode ==null){
           return false;
       }
       return code.equals(cacheCode);
    }
}

//输出到客户端
            ServletOutputStream sos = response.getOutputStream();
            /*JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(sos);
            encoder.encode(bi);*/
            ImageIO.write(bi, "PNG", sos);
            sos.flush();

<dependency>
            <groupId>org.springframework.session</groupId>
            <artifactId>spring-session-data-redis</artifactId>
            <version>2.1.12.RELEASE</version>
</dependency>

@EnableRedisHttpSession(maxInactiveIntervalInSeconds = 86400)