jquery 下载图片另存为

1，场景：附件列表上传操作字段，有一个下载按钮，现在附件，当附件类型为图片时，A标签无法另存为。
2，解决办法，采用表单提交的方式，由后端java处理完，采用iamgeIo输出到页面。
前端代码

js

function downloadImg(imagePathURL){
        $("#queryForm").attr("action","${request.getContextPath()}/ajaxUpload/downloadPic");
        $("#queryForm").submit();
    }

java代码

def downloadPic(){
        String path = params.path;
        String[] spUrl = path.toString().split("/");
        int len = spUrl.length;
        String endUrl = spUrl[len - 1];
        int dot = endUrl.lastIndexOf('.');
        String suffix = endUrl.substring(dot + 1, endUrl.length());

        URL url = new URL(path);
        BufferedImage img = ImageIO.read(url);

        response.setContentType("application/octet-stream");
        response.setHeader("Content-Disposition", "attachment;filename=".concat(String.valueOf(URLEncoder.encode(endUrl, "UTF-8"))));

        OutputStream os = response.getOutputStream();

        ImageIO.write(img,suffix,os);

        os.close();
    }

3，效果
[img]http://dl2.iteye.com/upload/attachment/0099/4279/e32123ef-bf55-36de-80e3-c22b82ca7952.jpg[/img]