JSP中的MongoDB输入流

Question

我正在尝试编写一个方法，该方法接受存储在mongoDB中的JSON对象并向用户提供ics / ics文件。 到目前为止，这是我的代码：

@RequestMapping(value = "/ical", method = RequestMethod.GET)
public void getIcalFile(
        String json,
        HttpServletResponse response) {
    try {
        // get your file as InputStream
        InputStream is = //Input stream from JSON. HOW?
        // copy it to response's OutputStream
        IOUtils.copy(is, response.getOutputStream());
        response.flushBuffer();
    } catch (IOException ex) {
        //log.info("Error writing file to output stream. Filename was '" + fileName + "'");
        throw new RuntimeException("IOError writinethod that takes a JSON object and serves a ical/ics file to the user. This is my code so far:g file to output stream");
    }

}

我不知道如何获取JSON对象并将其用作输入流。如果有更好的方法来实现我想要实现的目标，我会喜欢一个建议。