java利用captcha实验图片验证码

//前端页面

<dl>
    <dt><label class="title">验证码</label></dt>
    <dd>
        <input type="text" id="code" value="" maxlength="4" style="width: 172px;" placeholder="点击图片刷新">
        <img src="/captcha?width=153&height=33&number=4" id="codeImage" style="float: left" onclick="this.src='/captcha?width=153&height=33&number=4'" />
        <label class="msg"></label>
    </dd>
</dl>

/**
 * 验证码
 *
 * @param width  图片宽度
 * @param height 图片高度
 * @param number 验证码数量
 */
@RequestMapping(value = "/captcha")
public void captcha(HttpServletRequest request, HttpServletResponse response, int width, int height, int number) throws IOException {
    ConfigurableCaptchaService cs = new ConfigurableCaptchaService();
    cs.setColorFactory(new SingleColorFactory(new Color(25, 60, 170)));
    cs.setFilterFactory(new CurvesRippleFilterFactory(cs.getColorFactory()));
    RandomFontFactory ff = new RandomFontFactory();
    ff.setMinSize(30);
    ff.setMaxSize(30);
    RandomWordFactory rwf = new RandomWordFactory();
    rwf.setMinLength(number);
    rwf.setMaxLength(number);
    cs.setWordFactory(rwf);
    cs.setFontFactory(ff);
    cs.setHeight(height);
    cs.setWidth(width);

    response.setContentType("image/png");
    response.setHeader("Cache-Control", "no-cache, no-store");
    response.setHeader("Pragma", "no-cache");
    long time = System.currentTimeMillis();
    response.setDateHeader("Last-Modified", time);
    response.setDateHeader("Date", time);
    response.setDateHeader("Expires", time);

    ServletOutputStream stream = response.getOutputStream();
    String validate_code = EncoderHelper.getChallangeAndWriteImage(cs,
            "png", stream);

    request.getSession().setAttribute("REG_VAL_CODE", validate_code);

    stream.flush();
    stream.close();
}