1、生成验证码的工具类

可以直接用

将随机生成的验证码保存在session中

public class RandomValidateCodeUtil {


    public static final String RANDOMCODEKEY= "RANDOMVALIDATECODEKEY";//放到session中的key
    private String randString = "0123456789";//随机产生只有数字的字符串 private String
    //private String randString = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生只有字母的字符串
    //private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生数字与字母组合的字符串
    private int width = 95;// 图片宽
    private int height = 25;// 图片高
    private int lineSize = 40;// 干扰线数量
    private int stringNum = 4;// 随机产生字符数量

    private static final Logger logger = LoggerFactory.getLogger(RandomValidateCodeUtil.class);

    private Random random = new Random();

    /**
     * 获得字体
     */
    private Font getFont() {
        return new Font("Fixedsys", Font.CENTER_BASELINE, 18);
    }

    /**
     * 获得颜色
     */
    private Color getRandColor(int fc, int bc) {
        if (fc > 255)
            fc = 255;
        if (bc > 255)
            bc = 255;
        int r = fc + random.nextInt(bc - fc - 16);
        int g = fc + random.nextInt(bc - fc - 14);
        int b = fc + random.nextInt(bc - fc - 18);
        return new Color(r, g, b);
    }

    /**
     * 生成随机图片
     */
    public void getRandcode(HttpServletRequest request, HttpServletResponse response) {
        HttpSession session = request.getSession();
        // BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
        Graphics g = image.getGraphics();// 产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
        g.fillRect(0, 0, width, height);//图片大小
        g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18));//字体大小
        g.setColor(getRandColor(110, 133));//字体颜色
        // 绘制干扰线
        for (int i = 0; i <= lineSize; i++) {
            drowLine(g);
        }
        // 绘制随机字符
        String randomString = "";
        for (int i = 1; i <= stringNum; i++) {
            randomString = drowString(g, randomString, i);
        }
        logger.info(randomString);
        //将生成的随机字符串保存到session中
        session.removeAttribute(RANDOMCODEKEY);
        session.setAttribute(RANDOMCODEKEY, randomString);
        g.dispose();
        try {
            // 将内存中的图片通过流动形式输出到客户端
            ImageIO.write(image, "JPEG", response.getOutputStream());
        } catch (Exception e) {
            logger.error("将内存中的图片通过流动形式输出到客户端失败>>>>   ", e);
        }

    }

    /**
     * 绘制字符串
     */
    private String drowString(Graphics g, String randomString, int i) {
        g.setFont(getFont());
        g.setColor(new Color(random.nextInt(101), random.nextInt(111), random
                .nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(randString
                .length())));
        randomString += rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13 * i, 16);
        return randomString;
    }

    /**
     * 绘制干扰线
     */
    private void drowLine(Graphics g) {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x + xl, y + yl);
    }

    /**
     * 获取随机的字符
     */
    public String getRandomString(int num) {
        return String.valueOf(randString.charAt(num));
    }
}

2、前端页面代码

前端部分代码

注意src="login/getVerify"

代码

<body>
            <!--密码-->
            <div style="margin-top: 16px">
                <input type="password"
                       autocomplete="off" placeholder="登录密码" name="password"  id="password" required maxlength="32"/>
            </div>
            <!-- 验证码  -->
            <div style="margin-top: 17px">
                <input type="text"
                       autocomplete="off" placeholder="验证码" name="verify"  id="verify" required maxlength="32"/>
                <a href="javascript:void(0);" title="点击更换验证码">
                    <img id="imgVerify" src="login/getVerify" alt="更换验证码" height="36" width="170" onclick="getVerify(this);">
                </a>
            </div>
</body>
<!--js中的代码-->
<script type="text/javascript" src="./js/jquery.min.js"></script>
<script>

    //获取验证码
    /*function getVerify(obj){
        obj.src =  "login/getVerify?"+Math.random();//原生js方式
    }*/
	
	//获取验证码
    function getVerify() {
        // $("#imgCode").on("click", function() {
        $("#imgVerify").attr("src", 'login/getVerify?' + Math.random());//jquery方式
        // });
    }
    function aVerify(){
        var value =$("#verify_input").val();
        // alert(value);
        $.ajax({
            async: false,
            type: 'post',
            url: 'login/checkVerify',
            dataType: "json",
            data: {
                verifyInput: value
            },
            success: function (result) {
                if (result) {
                    alert("success!");
                } else {
                    alert("failed!");
                }
                // window.location.reload();
                getVerify();
            }
        });
    }
</script>

3、编写Controller以让验证码图片显示在前端

前端的src是"login/getVerify"
在controller中调用之前写好的验证码图片生成类

@RestController
@RequestMapping("/login")
public class PictureVerify {

    /**
     * 生成验证码
     */
    @RequestMapping(value = "/getVerify")
    public void getVerify(HttpServletRequest request, HttpServletResponse response) {
        try {
            response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片
            response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容
            response.setHeader("Cache-Control", "no-cache");
            response.setDateHeader("Expire", 0);
            RandomValidateCodeUtil randomValidateCode = new RandomValidateCodeUtil();
            randomValidateCode.getRandcode(request, response);//输出验证码图片方法
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 校验验证码
     */
    @RequestMapping(value = "/checkVerify", method = RequestMethod.POST,headers = "Accept=application/json")
    public boolean checkVerify(@RequestParam String verifyInput, HttpSession session) {
        try{
            //从session中获取随机数
            String inputStr = verifyInput;
            String random = (String) session.getAttribute("RANDOMVALIDATECODEKEY");
            if (random == null) {
                return false;
            }
            if (random.equals(inputStr)) {
                return true;
            } else {
                return false;
            }
        }catch (Exception e){
            return false;
        }
    }
}