GWT文件上传

Question

I have a following problem - we are using FormPanel which sends file to the Servlet which takes the arguments and tries to parse XML from this file. This works fine.

Problem is when the user uploaded a wrong file, so parsing ends with SAXException which I would like to propagate (or the exception's message) to client. I tried something like

catch (SAXException ex) {
    response.setStatus(HttpServletResponse.SC_UNSUPPORTED_MEDIA_TYPE);
    response.flushBuffer();
}

but it's not working, I always get empty tag pre ( <pre></pre> ). I am trying to catch this with

formPanel.addSubmitCompleteHandler(new SubmitCompleteHandler() {

    @Override
    public void onSubmitComplete(SubmitCompleteEvent event) {
        String s = event.getResults();
    });

I can use response.getWriter().write("Error"); in my Servlet but how the client will know if the error really occured or not?Using something like event.getResults().contains("error") doesn't seem to me as a correct solution.

So I am thinking about using RequestBuilder but I don't see a way how could I get the the uploaded file and push it to my servlet. Or maybe converting my message to JSON would help?

Answer 1

You should refer to this thread on the google gwt discussion group. The way you described, parsing the event.getResults() to determine if there was an error or the result in case of a success is the correct way to do it, even though it might seem barbaric.

As suggested in the linked discussion, you can look into GWT Upload for cleaner code, as well as upload progress information. I believe your only two options to upload files to a server from a web page are forms or Flash.