File upload progress bar using RestTemplate.postForLocation

Question

I have a Java desktop client application that uploads files to a REST service.

All calls to the REST service are handled using the Spring RestTemplate class.

I'm looking to implement a progress bar and cancel functionality as the files being uploaded can be quite big.

I've been looking for a way to implement this on the web but have had no luck.

I tried implementing my own ResourceHttpMessageConverter and substituting the writeInternal() method but this method seems to be called during some sort of buffered operation prior to actually posting the request (so the stream is read all in one go before sending takes place).

I've even tried overriding the CommonsClientHttpRequestFactory.createRequest() method and implementing my own RequestEntity class with a special writeRequest() method but the same issue occurs (stream is all read before actually sending the post).

Am I looking in the wrong place? Has anyone done something similar.

A lot of the stuff I've read on the web about implementing progress bars talks about staring the upload off and then using separate AJAX requests to poll the web server for progress which seems like an odd way to go about it.

Any help or tips greatly appreciated.

Answer 1

This is an old question but it is still relevant.

I tried implementing my own ResourceHttpMessageConverter and substituting the writeInternal() method but this method seems to be called during some sort of buffered operation prior to actually posting the request (so the stream is read all in one go before sending takes place).

You were on the right track. Additionally, you also needed to disable request body buffering on the RestTemplate's HttpRequestFactory, something like this:

HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory();
clientHttpRequestFactory.setBufferRequestBody(false);
RestTemplate restTemplate = new RestTemplate(clientHttpRequestFactory);

Here's a working example for tracking file upload progress with RestTemplate.