java 下载功能的实现

在jsp中有一个a标签 ，当用户点击a标签的时候下载文件。

我们采用href属性直接指向一个服务器地址，只要链接的文件存在,就会给出弹出保存对话框.

点击a标签 先执行onclick事件，再请求href中指向的地址。

前端jsp：

<a href="#" onclick="javascript:downloadtest('${app.id}')"  id="pluginurl"  style="color: #83AFE2;text-decoration:underline;"></a>

然后在js中：

 function downloadtest(id){
var url = "<%=request.getContextPath()%>/app/download" + "/" + id;
$("#pluginurl").attr("href",url);
}

后台java代码： 我的是springmvc

[java] view plaincopy

/**
     * 下载文件
     * @param id appid
     * @param response
     */
    @RequestMapping(value="/download/{id}")
    public void download(@PathVariable String id, HttpServletResponse response){
        String filepath = "";
        Result result = appService.getAppById(id);
        App app = (App) result.getMap().get("app");
        if(app == null){
            return;
        }
        filepath = app.getUrl();

        File file = new File(filepath);
        InputStream inputStream = null;
        OutputStream outputStream = null;
        byte[] b= new byte[1024];
        int len = 0;
        try {
            inputStream = new FileInputStream(file);
            outputStream = response.getOutputStream();

            response.setContentType("application/force-download");
            String filename = file.getName();
            filename = filename.substring(36, filename.length());
            response.addHeader("Content-Disposition","attachment; filename=" + URLEncoder.encode(filename, "UTF-8"));
            response.setContentLength( (int) file.length( ) );

            while((len = inputStream.read(b)) != -1){
                outputStream.write(b, 0, len);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }finally{
            if(inputStream != null){
                try {
                    inputStream.close();
                    inputStream = null;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(outputStream != null){
                try {
                    outputStream.close();
                    outputStream = null;
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

注意：response.addHeader("Content-Disposition","attachment; filename=" + URLEncoder.encode(filename, "UTF-8"));