Flask 中的 GET 请求 - 从 python 后端向客户端发送数据

Question

I have a page that asks the user for informations, the user selects options and confirms his choice. The answers are sent to the backend, and a file is made. I want to send back the file to the user but for this I have to send information from the backend to the frontend.

I tried using "return render_template" and "redirect" but it didn't work

I have been told I have to do a GET request but I'm not sure how to do this, I know how to send data from client to server but I never did from server to client and I haven't found how to do this with Flask.

@app.route('/createdocument', methods=['POST', 'GET'])
#@login_required
def create_document():
    playlists = get_playlists()
    if request.method == "POST":
        request_data = str(request.data.decode('UTF-8'))
        genre = get_header_genre(request_data)
        parsed_data = parse_request(request_data)           
        playlist_names = get_parsed_playlists(parsed_data)
        if genre == "playlist":
            #make_playlist_doc(playlist_names, genre)
            print("playlist option not ready yet")
        elif genre == "socan":
            name = make_socan_doc(playlist_names, genre)
            return render_template("tools/downloadfile.html", document=name)
        else:
            print("other request:")
            print(str(request.data.decode('UTF-8')))
    if request.method == "GET":
        ########################## Something I guess but I don't know what
   return render_template("tools/createdocument.html", playlists=playlists)

I found this looking for a GET request

function httpGetAsync(theUrl, callback)
{
    var xmlHttp = new XMLHttpRequest();
    xmlHttp.onreadystatechange = function() { 
        if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
            callback(xmlHttp.responseText);
    }
    xmlHttp.open("GET", theUrl, true); 
    xmlHttp.send(null);
}

If I understand well I should but /createdocument in theUrl, but what should I put in callback?

Answer 1

I think you are on the right track with the return render_template approach. What exactly isn't working?

For the client - can you use axios or fetch instead; those are fairly common libraries these days to get GET requests from the client.

axios.get('/createdocument', {
    params: {}
  })
  .then(function (response) {
    console.log(response);
  })
  .catch(function (error) {
    console.log(error);
  })
  .finally(function () {
    // always executed
  });   

That said if you are trying to do all of this asynchronously (ie the user submits the POST request and the file is not returned as part of that request, but is returned at some arbitrary later time), look into something like setting up a web socket

Here is a Flask-based websocket server that should work