Get opened input stream from rest template for large file processing

Question

I am looking for a way to get opened input stream from rest template - I was trying to used ResponseExtractor, but the stream is getting closed before returning, as written here:

https://jira.spring.io/browse/SPR-7357

"Note that you cannot simply return the InputStream from the extractor, because by the time the execute method returns, the underlying connection and stream are already closed"

I hope that there is a way and I will not have to write to my output stream directly in the rest template.

Answer 1

I didn't find a way to do it, the stream is always getting closed. As a workaround I created the following code:

public interface ResourceReader {
    void read(InputStream content);
}

with the following implementation:

public class StreamResourceReader implements ResourceReader {

private HttpServletResponse response;

public StreamResourceReader(HttpServletResponse response) {
    this.response = response;
}

@Override
public void read(InputStream content) {
    try {
        IOUtils.copy(content, response.getOutputStream());
    } catch (IOException e) {
        throw new IllegalStateException(e);
    }
}
}

then in controller:

@RequestMapping(value = "document/{objectId}")
public void getDocumentContent(@PathVariable String objectId, HttpServletResponse response) {
    ResourceReader reader = new StreamResourceReader(response);
    service.readDocumentContent(objectId, reader);
}

call to rest template:

restTemplate.execute(uri, HttpMethod.GET, null,
            new StreamResponseExtractor(reader));

and the string response extractor:

@Override
public ResponseEntity extractData(ClientHttpResponse response) throws IOException {
    reader.read(response.getBody());
    return null;
}

and it works like a charm! :)