Consider adding a progress listener for Callback

[joshgontijo]

From #26

One thing that would make this library even better is to add a simple progress callback that updates as a request is made. For POST/PUT/PATCH etc it would be great for this to monitor upload progress, and for GET/DELETE etc it would be great for download progress. Thoughts? This is another side note, but it would be nice to include a default callback class that provides stubbed implementations of the callback interface for those who don't wish to provide functionality for some of the methods.

Future<HttpResponse<JsonNode>> future = Unirest.post("http://httpbin.org/post")
  .header("accept", "application/json")
  .field("param1", "value1")
  .field("param2", "value2")
  .asJsonAsync(new Callback<JsonNode>() {

    public void failed(UnirestException e) {
        System.out.println("The request has failed");
    }

    public void completed(HttpResponse<JsonNode> response) {
         int code = response.getCode();
         Map<String, String> headers = response.getHeaders();
         JsonNode body = response.getBody();
         InputStream rawBody = response.getRawBody();
    }

    public void cancelled() {
        System.out.println("The request has been cancelled");
    }

    public void progress(long current, long total) {
        System.out.println("Progress: " + ((float)current / (float)total));
    }

});

[smarg120]

I saw this feature is being requested for 3 years without response....I switched to jodd http client that has this feature.

[joshgontijo]

@smarg120, I think the maintainers abandoned the original Unirest. I will have a look on jodd http, never heard of it.