昨天做SpringMVC 文件上传下载功能时遇到一堆问题。其中有个问题就是txt css js html xml pdf 等等文件下载时浏览器（html5的a标签download属性不是所有浏览器都支持的）是直接打开,而不是下载保存。网上有许多解决的方法，我这边只是整合下，做个mark。

场景就是有个url，老大提醒说用后台访问url获取文件流 前台来处理。。大概这个流程 代码如下：

前端js部分，参考http://www.alloyteam/2014/01/use-js-file-download/

//得到拼接字符串
function getFJInfo(name, url) {
	return "<tr><td style=''><a  href='javascript:void(0)' οnclick='getDownFile(\"" + url + "\",\"" + name + "\")'>" + name + "</a></td></tr>"
}
//文件下载
function getDownFile(url, name) {
	var param = {
		"url": url
	};
	$.ajax({
		url: contextPath + '/product-label/file2Stream',
		type: 'GET',
		data: Base64.encode(JSON.encode(param)),
		dataType: "text",
		success: function(data) {
			downloadFile(name, data)
		}
	})
}
//流处理触发下载事件
function downloadFile(fileName, content) {
	var aLink = document.createElement('a');
	var blob = new Blob([content]);
	var evt = document.createEvent("MouseEvents");
	evt.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
	aLink.download = fileName;
	aLink.href = URL.createObjectURL(blob);
	aLink.dispatchEvent(evt)
}

后台controller处理，参考http://blog.sina/s/blog_87216a0001014sm7.html

/**
     * 返回流
     * 
     * @param requestMap 请求参数
     * @param response 返回对象
     */
    @RequestMapping(value = "/file2Stream", method = RequestMethod.GET)
    public void file2Stream(@Json Map<String, Object> requestMap, HttpServletResponse response) {
        try {
            String url = String.valueOf(requestMap.get("url"));
            // URL url =new URL(String.valueOf(requestMap.get("url")));
            InputStream iStream = getFileStream(url);
            OutputStream stream = response.getOutputStream();
            stream.write(StreamUtils.getBytes(iStream));
            stream.flush();
            stream.close();
        } catch (Exception e) {
            LOG.error("ProductSalesRecommendController.file2Stream  error | ({})", e);
        }
    }

    /**
     * HttpURLConnection获取网络路径的文件流
     * 
     * @param url 链接
     * @return InputStream
     * @throws IOException
     */
    private InputStream getFileStream(URL url) throws IOException {
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setConnectTimeout(5 * 1000);
        conn.setRequestMethod("GET");
        InputStream inStream = conn.getInputStream();
        return inStream;
    }

    /**
     * HttpClient获取网络路径的文件流
     * 
     * @param url 链接字符串
     * @return InputStream
     * @throws IllegalStateException
     * @throws IOException
     */
    private InputStream getFileStream(String url) throws IllegalStateException, IOException {
        HttpParams httpParams = new BasicHttpParams();
        HttpConnectionParams.setConnectionTimeout(httpParams, 5000); // 设置连接超时为5秒
        HttpClient client = new DefaultHttpClient(httpParams); // 生成一个http客户端发送请求对象
        HttpResponse httpResponse = client.execute(new HttpGet(url)); // 发送请求并等待响应
        HttpEntity entity = httpResponse.getEntity(); // 获取响应里面的内容
        InputStream inStream = entity.getContent();
        return inStream;
    }