<!--图片验证码-->
<div>
    <div>
        <input type="text" id="codeYZM" placeholder="请输入验证码" maxlength="4">
    </div>
    <div>
        <a href="javascript:void(0);" title="点击更换验证码">
            <img id="imgYZM" src="" alt="更换验证码" onclick="getYZM(this);">
        </a>
    </div>
</div>
<script type="text/javascript">
    var imgYZM = $("#imgYZM").get(0);
    $(function () {
        getYZM(imgYZM);
    });
//    图片验证码
    function getYZM(obj) {
        obj.src = httpRequestUrl+"/getYZMPic?"+Math.random();
    }
</script>

@RequestMapping(value="/getYZMPic",method = RequestMethod.GET)
public void getYZMPic(HttpServletResponse response, HttpSession session) {
    OutputStream out = null;
    try {
        // 设置响应类型
        response.setContentType("image/jpg");
        // 获取创建验证码工具类实例
        CreateYZMCodeUtils yzm = CreateYZMCodeUtils.getInstance();
        // 获取生成的验证码字符串
        String code = yzm.getCreateYZMCode();
        // 将验证码存放在session
        session.setAttribute("code", code);
        // 获取验证码图片
        BufferedImage img = yzm.getCreateYZMImg(code);
        out = response.getOutputStream();
        // 通过ImageIO写出图片
        ImageIO.write(img, "jpg", out);
        out.flush();//强制将缓冲区中的数据发送出去

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

            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

public class CreateYZMCodeUtils {
    private Integer width;//验证码图片宽度
    private Integer height;//验证吗图片高度
    private Integer num;//验证码的个数
    private String code;//生成验证码一组字符串

    private static final Random ran=new Random();//随机数
    private static CreateYZMCodeUtils createYZMCodeUtils;
    /**
     * 通过默认构造初始化参数
     */
    private CreateYZMCodeUtils(){
        width=100;
        height=30;
        code="123456789adcdefghijklmnopqrstuvwxyz";
        num=4;
    }
    /**
     * 利用单利模式创建该验证码工具类
     * @return
     */
    public static CreateYZMCodeUtils getInstance(){
        if(createYZMCodeUtils==null){
            createYZMCodeUtils=new CreateYZMCodeUtils();
        }
        return createYZMCodeUtils;
    }
    public Integer getWidth() {
        return width;
    }

    public void setWidth(Integer width) {
        this.width = width;
    }

    public Integer getHeight() {
        return height;
    }

    public void setHeight(Integer height) {
        this.height = height;
    }

    public Integer getNum() {
        return num;
    }

    public void setNum(Integer num) {
        this.num = num;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public static Random getRan() {
        return ran;
    }
    public void setCreateYZMCodeUtils(Integer width,Integer height,Integer num,String code){
        this.width=width;
        this.height=height;
        this.num=num;
        this.code=code;
    }
    public void setCreateYZMCodeUtils(Integer width,Integer height,String code){
        this.width=width;
        this.height=height;
        this.code=code;
    }
    /**
     * 随机生成验证码 生成验证码的一组字符串
     * @return
     */
    public String getCreateYZMCode(){
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < num; i++) {
            sb.append(code.charAt(ran.nextInt(code.length())));
        }
        return sb.toString();
    }
    /**
     * 生成buffere Image图片
     * @param finshCode 生成好的验证码字符串
     * @return
     */
    public BufferedImage getCreateYZMImg(String finshCode){
        // 创建BufferedImage对象
        BufferedImage img = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);
        Graphics2D graphic = img.createGraphics();// 创建画笔
        graphic.setColor(Color.WHITE);// 设置颜色
        graphic.fillRect(0, 0, width, height);//是用预定的颜色填充一个矩形，得到一个着色的矩形块。
        graphic.setColor(Color.black);
//        graphic.drawRect(0, 0, width - 1, height - 1);// 画正方形
        // 设置字体 风格 风格 高度
        Font font = new Font("微软雅黑", Font.BOLD + Font.ITALIC,(int) (height * 0.8));
        graphic.setFont(font);
        for (int i = 0; i < num; i++) {
            // 随机设置字体RGB颜色
            graphic.setColor(new Color(ran.nextInt(255), ran.nextInt(255),ran.nextInt(255)));
            // 画出验证码
            graphic.drawString(String.valueOf(finshCode.charAt(i)), i* (width / num) + 4, (int) (height * 0.8));
        }
        for (int i = 0; i < (width + height); i++) {
            // 随机设置字体RGB颜色
            graphic.setColor(new Color(ran.nextInt(255), ran.nextInt(255),ran.nextInt(255)));
            // 生成干扰点
            graphic.drawOval(ran.nextInt(width), ran.nextInt(height), 1, 1);
        }
        for(int i = 0; i <2; i++){
            // 随机设置字体RGB颜色
            graphic.setColor(new Color(ran.nextInt(255), ran.nextInt(255),ran.nextInt(255)));
            // 随机生成干扰线
            graphic.drawLine(0, ran.nextInt(height), width,ran.nextInt(height));
        }
        return img;
    }
}